. .7.

. A. . ‘ I; .i. . ;
, . f .
.9: .

twang" A _ ‘ . A .1...
I“ *‘vld

1.

 

7%! l.
. .E .t
t .ua...

 

 

 

 

 

V- a. .1
. . \ i a
P}. Land. :2.

 

 

 

 

 

. ..i a. . , ., .,£1..!waﬂ.
waﬁkvﬂ ; ‘ , . . I: ..

 

This is to certify that the
dissertation entitled

A Novel Application of Ozone Chemistry for Biodiesel
Improvement: Product Development and Characterization

presented by
Tylisha Marie Baber

has been accepted towards fulfillment
of the requirements for the

PhD. degree in Chemical Engineering

CW AN; N Mk}, (LA/J

 

  

Major Professor’s Signature’J
Dec 0 Cl, 4m 5

Date

MSU is an Afﬂnnative Action/Equal Opportunity Institution

 

 

LIBRARY
Michigan State
University

PLACE IN RETURN Box to remove this checkout from your record.
TO AVOID FINES return on or before date due.
MAY BE RECALLED with earlier due date if requested.

 

DATE DUE DATE DUE DATE DUE

DE§ 29 68W}

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2/05 p:/ClRC/DaleDue.indd-p.1

A NOVEL APPLICATION OF OZONE CHEMISTRY FOR BIODIESEL
IMPROVEMENT: PRODUCT DEVELOPMENT AND CHARACTERIZATION

By

Tylisha Marie Baber

A DISSERTATION

Submitted to
Michigan State University
in partial fulﬁllment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY
Department of Chemical Engineering and Materials Science

2005

ABSTRACT

A NOVEL APPLICATION OF OZONE CHEMISTRY FOR BIODIESEL
IMPROVEMENT: PRODUCT DEVELOPMENT AND CHARACTERIZATION

By
Tylisha Marie Baber

Although there are numerous beneﬁts to utilizing biodiesel as an alternative fuel,
several challenges still remain, including poor oxidative stability, viscosity, volatility, and
low-temperature ﬂow properties. These research challenges are due to the structural
properties of biodiesel. The speciﬁc goal of this research study was to modify biodiesel
using ozone chemistry to improve its overall fuel quality. The oxidative cleavage of a
mixture of alkenes in biodiesel was conducted at room temperature in a gas washing
bottle-type reactor equipped with a fritted disc. Methanol was used as a reactant in a 2:1
alcohol to fuel molar ratio; and calcium carbonate was used as the catalyst at 10 wt% of
the starting fuel amount.

F TIR and GC/MS analysis conﬁrmed that the double bonds in methyl soyate were
successfully cleaved by ozone-mediate oxidation. The total amount of double bonds in
the mixture was reduced by more than 90% after three hours of ozonolysis. FTIR and
1H NMR indicated the presence of hydroperoxides and ozonides in the ozonated fuel.
However, these products thermally decomposed during the GC/MS analysis, producing
additional methyl esters. Hydroperoxide formation may have been the result of water, a
by-product in the conversion of both the hemiacetal and hydroperoxide intermediates to
methyl esters, reacting with the secondary ozonide. Another possible route for
hydroperoxide production is the reaction of the carboxyl oxide intermediate with

methanol. Ozonide formation was most likely due to the steric hindrance in the biodiesel

molecule. GC/MS analysis also conﬁrmed that three of the ﬁve expected esters for the
ozonolysis of methyl soyate- methyl hexanoate, nonanoate, and azelate-were formed
during the ozonation experiments. Two derivative forms of dimethyl malonate were
detected in the volatile fraction.

Similar products were formed in the ozonation and autoxidation of methyl soyate.
It was also found that the amount of double bond degradation was signiﬁcantly lower
when ozone was not the primary oxidant. Thus, it can be deduced that ozone was
simultaneously inducing lipid oxidation (ozone-induced oxidation) and oxidatively
cleaving the alkene moiety (ozonolysis) of biodiesel.

According to TGA analysis, the volatility of methyl soyate became comparable to
that of No. 2 diesel fuel after 3 hours of ozone-mediated oxidation. Two maximums
occurred for the rate of weight loss during TGA of ozonated methyl soyate. The ﬁrst
maximum occurred at 210°C from the presence of the long, hydrocarbon chains of the
starting esters and the second maximum occurred at 145°C from the presence of more
volatile products formed after ozonation. One broad maximum occurred at about 150°C
for No. 2 diesel fuel. The DSC cooling thermograms for methyl soyate exhibited two
major exothermic regions: region 1 between -10°C and -15°C and region 2 under -65°C.
There was a slight increase in both Tc. and Ta after a reaction time of 60 mins. This
observation was most likely due to the presence of monomeric and polymeric ozonides in
the product mixture. Selected low-temperature flow properties were evaluated for methyl
soyate. It was concluded that these properties were not enhanced for the ozonated fuel

due to the presence of ozonides.

DEDICATION
This dissertation is dedicated to MY PEOPLE-from ancestral, slavery, civil rights

movement, to now. They sacriﬁced their lives for the future generations, like me, to have
an equal educational opportunity.

iv

ACKNOWLEDGEMENTS

I would like to first of all thank the Trinity: God, Jesus Christ, and the Holy Spirit.
Throughout this process, God has pruned me so that I could regain my conﬁdence in Him
and, as a result, have a stronger faith-walk with Him. I thank my parents, Professors
Willie Lorenzo and Ceola Ross Baber, for their love and planting the seed in me by
always stressing the importance of education. I also thank my two siblings, Lorenzo
DuBois and Cheickna St. Clair Baber, for their support and love.

I thank my research advisor, Dr. Ramani Narayan, for his candid advise, wisdom,
and patience. I thank Dr. Daniel Graiver and Ken Farminer for their additional support
and help. I thank my Ph.D. committee members- Drs. Lira, Dale, Worden, Dolan- for
serving on my committee. I thank all of my current and past friends of the BMRC
(SINAS) research group — Chisa, Alison, Laura, Madhu, Yogaraj, Ben, Weipeng,
Guoren, Sunder, and Phuong. I thank Mike Rich for training me on the analytical
equipment in the CMSC and allowing me to have unlimited access to the lab! I thank
Drs. Mackay (Tiffany and Dave), Mohanty (Yash), and Steffe for allowing me to use
their analytical equipment. 1 thank Bev Chamberlin, Dr. Holmes, and Savant, Inc.. for
conducting the GC/MS, NMR, and selected fuel properties analysis, respectively.

I thank all of my brothers and sisters of Ebenezer Missionary Baptist Church for
their spiritual support and prayers. In particular, 1 thank Pastor Rodney and Sis. Charlene
Patterson for being my spiritual parents; and Rev. Keith Bigelow and Elder Demetrius
Marlowe for being my spiritual teachers and mentors. I also want to thank my
companion, Dr. Terence Brown, who came into my life at an unexpected time, but has

truly been a blessing in my life!

TABLE OF CONTENTS

LIST OF TABLES ............................................................................... viii
LIST OF FIGURES .............................................................................. x
Chapter 1: Introduction
1.1 Research Rationale & Motivation ....................................................... 1
1.2 Vegetable Oil Chemistry .................................................................. 3
1.3 Biodiesel Fuel Research & Development .............................................. 5
1.4 Research Problem Description ........................................................... 8
1.5 Ozone Chemistry ............................................................................ 15
1.6 Research Hypothesis ...................................................................... 18
1.7 Speciﬁc Goal & Research Objectives ................................................... 21
1.8 Organization of Dissertation ............................................................. 22
Chapter 2: Literature Review
2.1 Pyrolysis ..................................................................................... 23
2.2 Dilution ..................................................................................... 28
2.3 Microemulsion ............................................................................. 30
2.4 Transesteriﬁcation ......................................................................... 33
2.4.1 Mechanism & Kinetics ........................................................... 34
2.4.2 Effects of Moisture & Free Fatty Acids ....................................... 37
2.4.3 Effect of Molar Ratio ............................................................ 39
2.4.4 Effect of Catalyst Type .......................................................... 40
2.4.5 Effect of Reaction Time ......................................................... 42
2.4.6 Effect of Temperature ............................................................ 42
2.4.7 Effect of Mixing .................................................................. 43
2.4.8 Engine Performance ............................................................. 44
2.5 Summary of the Physicochemical Processes ................................. 45

Chapter 3: Materials & Methods

3.1
3.2
3.3
3.4

3.5

Chemicals .................................................................................. 46
Tranesteriﬁcation of Soybean Oil ....................................................... 47
Ozonolysis of Methyl Soyate ............................................................ 48
Structural Analysis ........................................................................ 50
3.4.1 Fourier Transform Infra-Red ................................................... 50
3.4.2 Nuclear Magnetic Resonance Spectroscopy .................................. 53
3.4.3 Gas Chromatography ............................................................ 53
3.4.4 Gas Chromatography/Mass Spectrometry .................................... 57
Thermal Analysis .......................................................................... 60
3.5.1 Thermogravimetrical Analysis .................................................. 60
3.5.2 Differential Scanning Calorimetry ............................................. 62
3.5.3 Low-Temperature Flow Properties ............................................. 65

vi

3.5.4 Viscosity Measurements ............................................................ 67

Chapter 4: Results & Discussion Part 1: Structural Analysis & Reaction Kinetics..... 71

4.] FTIR Analysis .............................................................................. 71
4.2 NMR Analysis .............................................................................. 79
4.3 GC Analysis ................................................................................ 80
4.4 GC/MS Analysis ........................................................................... 91
Chapter 5: Results & Discussion Part II: Thermal Analysis ............................... 107
5.1 TGA Analysis .............................................................................. 107
5.2 DSC Analysis .............................................................................. 111
5.3 Low-Temperature Flow Properties ...................................................... 115
5.3.1 Cloud, Pour, and Cold Filter Plugging Point Measurement .................. 115
5.3.2 Viscosity Measurement ............................................................ 116
Chapter 6: Conclusions, Future Work & Biodiesel Research Considerations ............ 118
6.1 Conclusions ................................................................................. 118
6.1.1 Structural Analysis ................................................................. 118
6.1.2 Thermal Analysis .................................................................. 120
6.2 Future Work ................................................................................ 122
6.2.1 Ozonide Analysis .................................................................. 122
6.2.2 Process Development and Mass Transfer Studies .............................. 122
6.2.3 Quality Assurance Test for Reliable Vehicle Operation ...................... 123
6.3 Other Uses of Biodiesel Fuel ............................................................ 124
References .......................................................................................... 125

vii

LIST OF TABLES

Table 1.1 Average Biodiesel Emissions Compared to Conventional Diesel ........... 7

Table 1.2 Properties of the Initial and Expected Product Esters ......................... 21
Table 2.1 Compositional Data of Pyrolyzed Oils .......................................... 24
Table 2.2 Comparative Fuel Properties of Soybean Oil and Diesel Fuel ............... 25
Table 2.3 Fuel Properties of Microemulsions .............................................. 32
Table 2.4 Fuel Properties of Soybean Esters ................................................ 44
Table 3.1 Spindle Geometric Parameters ................................................... 70
Table 4.] Characteristic Absorption Frequencies for Several Ozonides ................ 75
Table 4.2 Direct Conversion of Oleﬁns to Esters: Nomenclature and Yields .......... 76

Table 4.3 Theoretical and Experimental Absorption Frequency Ranges for
Common Functional Groups Present in Ozonated Methyl Soyate ......... 78

Table 4.4 Fatty Acid Composition of Transesteriﬁed, RB Soybean Oils ............... 81

Table 4.5 Reaction Rate Constants for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Palmitate, Stearate, Oleate Constituents ............................... 84

Table 4.6 Reaction Rate Constants for the Ozonolysis of Regular Methyl Soyate:
Methyl Palmitate, Stearate, Oleate Constituents ................................. 85

Table 4.7 Reaction Rate Constants for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Linoleate, Linolenate......... .......................................................... 88

Table 4.8 Reaction Rate Constants for the Ozonolysis of Regular Methyl Soyate:
Methyl Linoleate, Linolenate Constituents............................................ 88

Table 4.9 Reaction Order Constants for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Linoleate, Linolenate Constituents............................................ 88

Table 4.10 Reation Order Constants for the Ozonolysis of Regular Methyl Soyate:
Methyl Linoleate, Linolenate Constituents ..................................... 89

viii

Table 4.1 1

Table 4.12

Table 4.13

Table 4.14

Table 4.15

Table 4.16

Table 4.17

Table 5.1

Table 5.2

Table 5.3

Table 5.4

Table 5.5

Table 5.6

Table 6.1

Peak Identiﬁcations and Their Structures for Ozonated Low-Sat

Methyl Soyate at a Reaction Time of 180 mins ............................... 93
Mass Estimation for the Major Components in the Catalytic, Ozonated
Low-Sat Methyl Soyate at a Reaction Time of 180 mins .................... 97
Peak Identiﬁcations and Their Structures for Ozonated Low-Sat

Methyl Soyate at a Reaction Time of 180 mins: Volatile Fraction ......... 100
Products Formed During the Autoxidation of Methyl Oleate, Linoleate,

and Linolenate in the Present of Metallic Promoters .......................... 103
Volatile Compounds of the Thermally Decomposed Pure Hydroperoxides
from Autoxidized Methyl Oleate, Linoleate, and Linolenate ................ 104
Double Bond Decomposition Between the Autoxidation and Ozonolysis

of Regular Methyl Soyate .......................................................... 105
Peak Identiﬁcations and Their Structures for the Autoxidation of Regular

Methyl Soyate at a Reaction Time of 180 mins: Volatile Fraction .......... 106
Boling Point Data for Compounds Present in Ozonated Methyl Soyate. . .. 108

Freezing Point Data for Compounds Present in Ozonated Methyl Soyate. 1 12

Onset Crystallization Temperatures for Methyl Soyate ....................... 114
Physicochemical Properties of Cyclohexene Ozonides ....................... 1 15
Low-Temperature Flow Properties of Methyl Soyate and

No. 2 Diesel Fuel .................................................................. 1 15
Dynamic Viscosity Values of Selected Oils at 25°C .......................... 1 17
ASTM D 6751 Fuel Speciﬁcations .............................................. 123

ix

Figure 1.1
Figure 1.2
Figure 1.3
Figure 1.4
Figure 1.5

Figure 1.6

Figure 1.7

Figure 1.8

Figure 1.9
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 2.6
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4

Figure 3.5

LIST OF FIGURES

Sustainable Development Initiative Diagram ................................. 2

Basic Structure of a Triglyceride Molecule with Major Reactive Sites....4

Five Chemical Building Blocks for the OIeochemical Industry ............ 5
General Mechanism for Lipid Oxidation ....................................... 10
Resonance Structure of Ozone .................................................. 15

Criegee Mechanism for the Ozonolysis of the Alkene
Functional Group ................................................................. 16

A Typical Electric Discharge Ozone Generator .............................. 17

Mechanism for the Direct Conversion of Oleﬁns to Esters Via

Ozonoylsis ......................................................................... 19
Expected Ester Products from the Ozonolysis of Methyl Soyate .......... 20
Transesteriﬁcation Reaction of Vegetable Oil ................................ 33
Stepwise Conversion of Glycerides to Esters ................................. 35

Mechanism of Base-Catalyzed Transesteriﬁcation of Vegetable Oils. . .. 35

Saponiﬁcation of Ester ........................................................... 38
Hydrolysis of Triglyceride ...................................................... 38
Saponiﬁcation of Free Fatty Acid .............................................. 38

Experimental Apparatus for the Transesteriﬁcation of RB Soybean Oil..47

Process Flow Diagram for the Ozonolysis of Methyl Soyate ............... 50
A Typical Michelson Interferometer ........................................... 52
Basic Components of a Gas Chromatographic System ..................... 54
A Typical Mass Spectrometer ................................................... 59

Figure 3.6
Figure 3.7
Figure 3.8

Figure 3.9

Figure 3.10

Figure 4.1

Figure 4.2

Figure 4.3

Figure 4.4

Figure 4.5

Figure 4.6

Figure 4.7

Figure 4.8

Figure 4.9

Figure 4.10

Figure 4.11

Figure 4.12

Figure 4.13

Figure 4.14

TGA 2950 Thermogravimetrical Analyzer .................................... 61
Cell Compartment of a Differential Scanning Calorimeter ................. 63
General Apparatus for Cloud and Pour Point Measurement ................ 66
General Apparatus for Cold Filter Plugging Point Measurement .......... 67
SearIe-Type Rotational Viscometer ............................................ 68

F TIR Spectra for the Catalytic Ozonolysis of Low- Sat Methyl Soyate. 71

F TIR Spectra for the Catalytic Ozonolysis of Low- Sat Methyl Soyate:

Region A .......................................................................... 73
FTIR Spectra for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:

Region B ........................................................................... 74
Direct Conversion of Oleﬁns to Esters ........................................ 76

FTIR Spectra for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:

Volatile Fraction .................................................................. 77
IH NMR Spectra for Non-Ozonated Low-Sat Methyl Soyate .............. 80
lH NMR Spectra for the Catalytic Ozonolysis of Low-Sat

Methyl Soyate ..................................................................... 80
Chromatogram of Transesteriﬁed Low-Sat Soybean Oil ................... 81
Chromatogram of Transesteriﬁed Regular Soybean Oil ..................... 82

Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:
Methyl Palmitate, Methyl Stearate, Methyl Oleate Constituents ........... 84

Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:
Methyl Linoleate, Linolenate Constituents .................................... 87

Linear Relationship of the Kinetics for the Catalytic Ozonolysis of
Low-Sat Methyl Soyate: Methyl Linoleate, Linolenate Constituents. . 87

Relative Amounts of Double Bond Degradation for the Unsaturated
Moieties ............................................................................ 89

Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:
Methyl Hexanoate, Nonanoate and Dimethyl Azelate Ester Products. 90

xi

Figure 4.15

Figure 4.16

Figure 4.17
Figure 4.18
Figure 4.19

Figure 4.20

Figure 4.21
Figure 4.22

Figure 4.23

Figure 4.24

Figure 5.1

Figure 5.2

Figure 5.3

Figure 5.4

Chromatogram of Non-Ozonated Low-Sat Methyl Soyate ................. 92
Chromatogram of Ozonated Low-Sat Methyl Soyate at a

Reaction Time of 180 mins ...................................................... 92
Mass Spectra of Methyl Hexanoate ............................................ 94
Mass Spectra of Methyl Nonanoate ............................................ 95
Mass Spectra of Dimethyl Azelate ............................................. 95
Chromatogram of Ozonated Low-Sat Methyl Soyate at a Reaction Time

of 180 mins: Corresponding Volatile Fraction ............................... 99
Overall Reaction Mechanism for Acetal Formation ......................... 102
Hydrolysis of Ester ................................................................ 102
Chromatogram of the Autoxidation of Regular Methyl Soyate at a

Reaction Time of 180 mins ...................................................... 105

Chromatogram for the Autoxidation of Regular Methyl Soyate at a
Reaction Time of 180 mins: Volatile Fraction ................................ 106

TGA Proﬁles of Ozonated Low-Sat Methyl Soyate and

No. 2 Diesel Fuel ................................................................. 108
Plot of Derivative Weight Loss vs. Temperature for No. 2 Diesel Fuel

and Ozonated Methyl Soyate ................................................... 109
Plot of Derivative Weight Loss vs. Temperature for Regular and

Low-Sat Methyl Soyate ......................................................... 1 10
DSC Cooling Thermograms for Low-Sat Methyl Soyate ................... 1 12

Figure 5.5 Onset Crystallization Temperatures for Regions 1 and 2

as a Function of Reaction Time ................................................... 114

Figure 5.6 Viscosity as a Function of Time for Low-Sat and Ozonated

Low-Sat Methyl Soyate ............................................................ l 16

xii

Chapter 1
Introduction

1.1 Research Rationale & Motivation

Economic development and growth in the 20th century was driven by the use of
crude oil, coal, and natural gas as raw materials for chemical, material, and energy
production. Gasoline and diesel fuel power almost all vehicles, while plastics made from
petroleum or natural gas are used to make clothes, food packaging, car parts, and building
materials. Most chemicals, even toiletries and pharmaceuticals, are petrochemically
derived. However, a new revolution spurred by the expanded use of renewable biobased
products and bioenergy will have a signiﬁcant impact in the 21St century. A new,
sustainable economy based on biomass feedstocks will bring numerous economical,
environmental, and societal beneﬁts to the United States, encompassing the sustainable
development initiative, illustrated in Figure 1.1. The mitigation of imported petroleum
with biorenewable resources will help strengthen national security by reducing our
nation’s dependence on foreign resources and becoming self-sufﬁcient in energy
production. Biobased products will improve environmental quality by reducing pollutant
emissions, like sulfur, heavy metals, and greenhouse gases, reducing soil erosion,
sequestering carbon, protecting water supplies and quality, and increasing the diversity of
agricultural crops and products. Finally, biobased products will revitalize rural

communities by introducing innovative crops and markets to the agricultural economy.

Carbon cycling

Land

Air

Water

Energy
0 Renewable
0 Fossil

 

ENVIRONIVIENT

  
     

 

 

I SOCIAL ECONOMICS

 

0 Community impact

0 Feedstock displaced
0 Stability
o Rural/Urban impact

0 Human capital

0 $$ ﬂow

 

Resource availability
Capacity to produce
Fossil vs renewable

Figure 1.1 Sustainable Development Initiative Diagram
Adopted from Ref. [1]

Biomass feedstocks consist of any plant-derived organic matter, including grain,
oilseeds, waste and residue crops, herbaceous and woody crops, and animal wastes. In
terms of bioreﬁnery, these constituents are chemically processed to a host of valuable and
marketable chemicals, materials, and energy, while generating minimal toxic emissions
and waste. A bioreﬁnery is, thus, analogous to a petroleum reﬁnery in that raw materials
are converted to both high-volume, commodity and high-value, specialty products. A
biobased economy cannot fully replace huge volumes of or eliminate the need for
petrochemicals. However, as existing bioreﬁning technologies are being improved and
innovative technologies are being developed, biobased products will mitigate the use of
competing petroleum-derived products, making the 21St century an increasingly

sustainable, domestic, and environmentally responsible one.

1.2 Vegetable Oil Chemistry

Fats and oils derived ﬁom plants serve a vital function both in the U. S. and world
economics for food and nonfood applications. Provided only with the simplest and most
inexpensive inputs of carbon dioxide, sunlight, water, and minerals, plants are efficient
and diverse chemical factories that serve as basic chemical blocks for the production of
sophisticated chemical molecules with many structural features [2]. Vegetable oils and
animal fats are triacylglycerols, also called triglycerides, consisting of three fatty acids
attached to a glycerol molecule. Many naturally occurring fats and oils are made up of
saturated and unsaturated fatty acids with a chain length greater than 12 carbon atoms,
with the vast majority having more than 16 carbon atoms. For the unsaturated moiety,
the double bonds are non-conjugated, or are interrupted by a methylene group
(-CH2-), and are in the cis conﬁguration.

From a chemical perspective, triglycerides have two reactive sites, the double
bonds of the unsaturated fatty acid chain (-R), and the carbonyl group (C = O), linking
the fatty acid to the glycerol, shown in Figure 1.2. With regard to product development,
the majority of derivatization reactions are carried out at the carbonyl group (>90%);
whereas oleochemical reactions involving the alkyl chain, or double bonds, represent less
than 10% [3]. On the industrial level, the most extensively applied reactions of the
double bonds are hydrogenation and epoxidation. Other reactions also include
polymerization, hydroxylation, metathesis, carboxylation, radical addition, and oxidative
cleavage. Reactions involving the carbonyl functional group include hydrolysis,

transesteriﬁcation, and amine synthesis.

I

:0“

I II \
CHz—O-T'C-i—Rj

I

l ' O I H H H H H

' ll . L- l.‘ I L- L
CH — o—‘c -‘—R2 where “R” 18 [CH2]n'£C_=__§rC‘€C ft; 7-[CH2],, -CH3
I | 0' [I

I
H
CH2 —0 —-\;C,J-—R3

reactive sites

Figure 1.2 Basic Structure of a Triglyceride Molecule with Major Reactive Sites
As a consequence of the two reactive sites, ﬁve core classes of oleochemicals,
including acids, alkyl esters, alcohols, amines, and glycerol, constitute the fundamental
chemical building blocks for the oleochemical industry, depicted in Figure 1.3. In fact,
about 30% of vegetable oils that are produced today are used by the oleochemical
industry for non-food products and applications [2]. Thus, chemical modiﬁcation of
vegetable oils is an important route to obtain industrial products using renewable
feedstock. There is still a research need and challenge to develop new efficient and
environmentally friendly reaction pathways leading to new products and to ﬁnd new

applications for already existing oleochemicals.

acetates, Iactates, tartrates, etc.

 

monoacylglycerols
diacylglycerols

 

GLYCEROL ‘_. Triglycerides _—>

 

 

sulfonates j. l J, F» metal salts

 

—>
ALCOHOLS 1:53;; e—ACIDS —> AMIDES. AMINES
f _’ ketene dimers
. . anhydrides

biodiesel acid chlorides
ethylene oxide adducts _’ peroxy acids/esters
sulfates
Guerbet alcohols

Figure 1.3 Five Chemical Building Blocks for the Oleochemical Industry
Adopted from Ref. [4]

1.3 Biodiesel Fuel Research & Development

The use of vegetable oils as fuel for diesel engines is not a new concept.

Dr. Rudolf Diesel ﬁrst developed the Diesel engine in 1895 with the full intention of
running it on a variety of fuels, including vegetable oil. Diesel showed his engine at the
World Exhibition in Paris in 1900 using peanut oil as fuel. In 1912 Diesel stated,

“The fact that fat oils from vegetable sources can be used may seem insigniﬁcant
today, but such oils may perhaps become in course of time of the same importance as
natural mineral oils and the coal tar products are now. One cannot predict what part these
oils will play in the Colonies in the future. In any case, they make it certain that motor-
power can still be produced from the heat of the sun, which is always available for
agricultural purposes, even when all our natural stores of solid and liquid fuels are
exhausted.” -Dr. Rudolph Diesel [5, 6]

Dr. Diesel’s words are truer today than ever before.

Biodiesel is a domestic, renewable fuel for diesel engine use, comprised of mono-

alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, which

meets the ASTM D6751 fuel quality standard. Biodiesel is produced by the

transesteriﬁcation of vegetable oils or animal fats with an alkyl alcohol to product alkyl

esters and glycerol, a valuable by-product. The most common type of biodiesel produced
is methyl esters, mainly because methanol is an inexpensive alcohol. Biodiesel is
biodegradable and non-toxic, being just as biodegradable as sugar and less toxic than
table salt. Studies have shown biodiesel to biodegrade up to four times faster than
petroleum diesel fuel, with up to 98% biodegradation in 3 weeks [7]. Moreover, no
engine modiﬁcations are needed to use biodiesel in a diesel engine.

Biodiesel is one of the most thoroughly tested alternative ﬁiels on the market. It
is the ﬁrst alternative fuel in the country to have a complete evaluation of emission
results and potential health effects submitted to the US. Environmental Protection
Agency (EPA) under the Clean Air Act Section 211 (b) [8]. These evaluations include
the most stringent emission testing protocols ever required by the EPA for certiﬁcation of
fuels and fuel additives. The data gathered complete the most thorough inventory of the
environmental and human health effects attributes that current technology will allow.
Biodiesl’s exhaust is essentially free of lead, sulfur and its derivatives, halogens, and has
reduced particulates, unburned hydrocarbons, carbon monoxide, and carbon dioxide.
Also, petroleum-derived diesel contains 20-40% (vol) of aromatic compounds, which
increase emissions of particulate matter and nitrogen oxides, NOx. On the other hand,
biodiesel is essentially non-aromatic. EPA has surveyed the large body of biodiesel
emissions studies and averaged the Health Effects testing results with other major studies.

These results are listed in Table 1.1.

Table 1.1 Average Biodiesel Emissions Compared to Conventional Diesel

 

Emission Type M m
Regglated

Unburned Hydrocarbons -67% -20%
Carbon Monoxide -48% -12%
Particulate Matter -47% -12%
Non-regglated

Sulfates & Sulfur Oxides -100% -20%
PAH (Polycyclic Aromatic Hydrocarbons) -80% -13%
nPAH -90% -50%

 

Source: Ref. [8]; “20% biodiesel blended with 80% petroleum diesel, by volume

Due to the large amount of soybean production in the U. S., biodiesel research
and development is focused on biodiesel derived from soybean oil, commonly referred to
as methyl soyate. In fact, soybean oil accounts for about 75% of the nation’s crop oil
production [2]. The soybean contains high quality protein (38-42%), oil (18-22%), and
meal (36-44%), which are recovered by hexane extraction [4]. Soybean meal is
primarily used as animal feed, but can also be a feedstock for manufacturing biobased
products. The oil is mainly used in food applications, oﬁen aﬁer partial hydrogenation,
as salad oil, cooking oil, and frying oil and in margarines and shortening. Non-food uses
are based mainly on the high levels of unsaturation and include coatings, epoxidized oil,
and dimer acids.

At present, the high cost of biodiesel is a major obstacle to its commercialization.
Roughly 75 to 90% of the cost of biodiesel is the raw materials. The current use and
price of food—grade soybean oil as the feedstock for biodiesel has caused the price for the
fuel to be about $2.50/ gal. Thus, reducing the cost of the feedstock is necessary for
biodiesel’s long-term commercial viability. One way to reduce its cost is to use less
expensive feedstocks like waste cooking oil and rendered animal fats, which will also

help solve the problem of waste oil disposal. However, the cost difference between

biodiesel and petrodiesel is already shrinking due to rising petroleum costs, new EPA
rules requiring reduced sulfur content in diesel, and improvement in the biodiesel
industry such as building larger plants with more efﬁcient production technology and
expanding the glycerol by-product market. In fact, the cost of gasoline reached a record-
high price of $2.06/gallon on average across the U. S. in June 2004; and in October of
that same year, US. light crude hit $55.67 a barrel, the highest level in 21 years of
recorded oil prices [9]. Thus, it’s a fairly safe assumption that if demand remains strong
and reserves and production capacity remain limited, there will be a general upward trend
in petroleum prices in the years to come. While some oil industry analysts insist that
current high prices are just a temporary situation, others have stated that oil prices
possibly have reached a new plateau and may not come down much at all, and that
further price increases are inevitable [9]. Therefore, assuming that petroleum prices
remain high and that the recently passed tax incentive for biodiesel will boost its industry,
the future of biodiesel in the U. S. is very promising.
1.4 Research Problem Description

Although there are numerous beneﬁts to utilizing biodiesel as an alternative fuel,
several challenges still remain, including poor oxidative stability, low-temperature ﬂow
properties, like viscosity, and volatility. These research challenges are inherent in the
structural properties of biodiesel.
Oxidative Stability

Oxidation is a major source of biodiesel contamination and is an area of great
concern in biodiesel research. Unsaturated fatty acid esters are subjected to oxidation, an

irreversible reaction of atmospheric oxygen with organic compounds. This reaction is

autocatalytic in nature, meaning that the rate of oxidation is slow at the beginning and
increases as the reaction progresses. Illustrated in Figure 1.4, the free radical chain
theory postulated by Farmer et al. [10] has been the generally accepted mechanism for
lipid oxidation. In the initiation step, a “quantum” of energy from an initiator, I, like heat
or light, catalyze the abstraction of an allylic hydrogen atom from an alkene functional
group. The resulting free radical, R-, readily reacts with oxygen to form a peroxyl free
radical, R000. The peroxyl free radical is highly reactive and, thus, can abstract an
allylic hydrogen atom from another unsaturated lipid molecule, propagating the cyclic
chain reaction to yield hydroperoxides. Oxygen can attack at each end of the allylic
system, producing a mixture of peroxyl radicals and yielding different positional
hydroperoxides. Hydroperoxides are the unstable primary products of lipid oxidation.
They decompose to stable secondary products, like aldehydes, ketones, alcohols,
hydrocarbons, esters, and polymers. It has been established that the oxidative stability of
fatty esters is directly related to the number of double bonds present in the molecule [11].
Thus, the rate of oxygen absorption is much higher in fatty esters containing multiple
double bonds than those containing single or no double bonds. In fact, the relative
autoxidation rate of methyl stearate, methyl oleate, methyl linoleate, and methyl
linolenate was found to be 1:11:114:170, respectively, at comparable temperatures[12]. It
was further concluded that the rate of oxidation of non-conjugated polyunsaturated fatty
esters is the fastest because of the high activation energy of methylene groups between
the double bonds [10]. Therefore, since biodiesel is produced from highly unsaturated
oils (85% by weight), it oxidizes more rapidly than diesel fuel. Although saturated fatty

esters are also susceptible to degradation by oxidation, the autoxidation is much slower.

R’ - H (allylic)
300 c =c— c’
L___l
1 R
RH noon

Figure 1.4 General Mechanism for Lipid Oxidation

The oxidative instability of biodiesel is of particular concern because it
contributes to long-term storage and engine/fuel systematic problems, having a negative
impact on its fuel quality. The products of oxidation adversely affect ﬁlCI storage life and
contribute to deposit formation in tanks and engine fueling systems. Furthermore,
hydroperoxides, the primary products of oxidation, can induce polymerization of the
esters, forming insoluble gums and sediments, which can cause fuel ﬁlter plugging. In
fact, the Engine Manufacturers Association (EMA) [13] has recently issued a warning
against using over 5% (vol) biodiesel in petrodiesel fuel because the poor oxidative
stability of biodiesel can cause a variety of engine performance problems, including ﬁlter
plugging, injector coking, piston ring sticking and breaking, and severe degradation of
engine lubrication. The Fuel Injection Equipment manufacturers have also expressed a
concern that fuel blends containing more than 5% (vol) biodiesel can cause reduced
product service life and injection equipment failure [14]. As for storage issues, the EMA
statement concluded that the poor oxidation stability of biodiesel fuels could result in
long-term storage problems due to deposit formation in tanks, fuel systems, and ﬁlters.
Many researchers have studied the oxidative stability of biodiesel from a variety of
feedstocks [15-20]. The major ﬁndings from these studies were that biodiesel should be

stored in darkness, at low temperatures, and under anaerobic conditions in order to

10

guarantee a consistent quality of the fuel. It was further recommended that the storage
period should not be longer than one year. Thus, improving the oxidative stability of
biodiesel is an important guide to product quality and performance.
Low- Temperature F low Properties

In spite of biodiesel’s many advantages, performance during cold weather may
affect its year-round commercial viability in moderate temperature climates. Structural
features of biodiesel that affect its low-temperature properties include the degree of
saturation, chain length, and degree of branching. Saturated fatty acids, which contain
only single carbon-carbon bonds, are chemically less reactive than the corresponding
fatty acids of the same chain length with one or more double bonds. Since they do not
contain any double bonds, saturated molecules can pack closely together. Therefore,
saturated fatty acids are solids at room temperature and have high melting points, which
increase with chain length. Biodiesel contains about 15% (wt) saturates, including
methyl palmitate and stearate. This rather high level of saturation causes biodiesel to be
less useful with decreasing temperature and major engine and ﬂow problems during the
winter season can be experienced. Although ﬁeld studies of biodiesel performance in
cooler weather are scarce, there is evidence that using the soybean methyl ester form of
biodiesel raises performance issues when ambient temperatures approach 0-2°C [21]. As
overnight temperatures fall into this range, the saturated methyl esters nucleate and form
solid crystals. If the fuel is left unattended in cold temperatures for a long period of time,
these crystals plug or restrict ﬂow through fuel lines and ﬁlters during start-up and can
lead to fuel starvation and engine failure. All biodiesel fuels exhibit poor cold-ﬂow

properties with cloud and pour points 15-20°C higher than those of petrodiesel fuel [22].

11

In particular, methyl soyate exhibits a cloud point near the freezing temperature (0°C)
compared to petroleum’s cloud point of about -16°C [23]. Similarly, the pour point of
methyl soyate is around -2°C compared with -27°C for petrodiesel [23]. These values are
relatively high when compared to winter ambient temperatures, making the use of
biodiesel limited in areas like Canada, the northern US, and much of Europe.

Possible solutions to the low-temperature ﬂow problems of biodiesel have been
investigated, including blending biodiesel with petrodiesel fuels, additives, winterization,
and the use of branched-chain esters. The most common application of vegetable oil
esters in the U. S. is their use in blends of conventional diesel fuel [24]. Methyl esters
from transesteriﬁed soybean oil were studied as neat fuels and in blends with petrodiesel
[23]. This research showed that blending methyl esters with conventional diesel ﬁrel
signiﬁcantly improved its low-temperature ﬂow properties. However, results from the
pour point, cloud point, and low-temperature ﬁlterability studies demonstrated signiﬁcant
limitations of blending esters with petroleum fuel to improve cold-ﬂow operability
because the methyl ester contents are held at relatively low blend ratios. Additives have
been reported to reduce the pour points of biodiesel fuels; however, they do not reduce
the cloud point nor improve the ﬁlterability of biodiesel [25]. A “winterization kit” was
then suggested as a solution for warming-up the fuel in cold weather [26]. A three-step
winterization process involves mixing in additives, chilling, equilibrating the fuel at a
temperature between its cloud and point points, and ﬁltering out the saturated
precipitates. This process leaves behind a liquid phase with an enhanced concentration of
unsaturated methyl esters. Consequently, the liquid product should demonstrate

improved cold-ﬂow properties. In a study conducted by Lee et al. [26], winterization of

12

neat methyl soyate produced a crystallization onset temperature (Tm) of -7.1°C,
compared to 37°C for the unwinterized methyl soyate. However, it was concluded that
winterization was not an efﬁcient way of removing saturated methyl esters or reducing
the TCO, due to the poor separation of the liquid phase from the crystalline fraction,
resulting in very low yields.

Crystallization involves the arrangement of molecules in an orderly fashion.
When branches are introduced into linear, long-chain esters, intrarnolecular associations
should be attenuated and crystallization temperatures reduced [27]. Thus, the
crystallization temperature of biodiesel should be improved by replacing the methyl or
ethyl ester with a branched moiety such as isopropyl. Indeed, isopropyl and 2-butyl
esters of soybean oil showed a lower Tm by 7-11°C and 12-14°C, respectively, than the
corresponding methyl esters [27]. Both the cloud and pour points were also lowered by
the branched-chain esters. Reducing chain length and/or increasing chain branching can
improve cold-ﬂow fuel properties. One way to alter the chain length and degree of
branching is through chemical processing of the biodiesel to cleave certain double bonds
or to form branched isomers. Very little practical research has been done in the chemical
processing area in terms of modifying the chemical structure of biodiesel. Thus, the cold-
ﬂow properties of biodiesel fuels are clearly an area in need of considerable research.
Viscosity & Volatility

Viscosity and volatility are two key fuel properties of diesel fuel relating to the
satisfactory performance of the fuel injection equipment. In the diesel engine, fuel is
injected as ﬁnely atomized spray into the combustion chamber, where it mixes with the

hot compressed air and ignites. Thus, viscosity and volatility affect the atomization of a

13

fuel upon injection into the combustion chamber, and thereby, the formation of engine
deposits.

For edible fats and oils, viscosity increases with increasing degree of saturation,
and decreases with decreasing carbon-chain hydrocarbon chain lengths that have lower
molecular weights. This holds true for the alcohol moiety because viscosity of ethyl
esters is slightly higher than that of methyl esters. Factors, such as double-bond
conﬁguration, inﬂuence viscosity (cis double-bonds give a lower viscosity than trans);
whereas the position of the double bonds has a lesser affect on viscosity. Moreover,
branching in the ester moiety has little or no inﬂuence on viscosity. Viscosities of neat
vegetable oils are nearly 10 times that of No. 2 diesel fuel [28, 29]. The molecular
weight of an ester molecule is roughly 1/3 that of the parent triglyceride molecule,
resulting in a viscosity about twice that of petrodiesel. Due to the presence of high
molecular weight constituents and a high level of unsaturation, biodiesel fuel has a lower
volatility than its petrodiesel counterpart. High viscosity and very low volatility lead to
poor atomization of the fuel, incomplete combustion, coking of the fuel injectors, ring
carbonization, and accumulation of fuel in the lubricating oil, resulting in serious engine
deterioration. Lubricating oil contamination is a result of the unsaturated fraction of the
fuel polymerizing, causing the oil to gel and requiring frequent oil changes.

1.5 Ozone Chemistry

Ozone, the triatomic allotrope of oxygen, has the formula O3, and generally exists
as a relatively unstable, reactive gas. In gaseous form, ozone is colorless, whereas liquid
ozone is almost non-transparent and bluish-black and its crystals are violet-blue. Ozone

exists naturally in large quantities in the upper atmosphere, where it absorbs ultraviolet

l4

light and acts as a screen to prevent this radiation from penetrating to the earth’s surface.
Ozone can be represented as a combination of its two most stable Lewis structures,

depicted in Figure 1.5.

00+ 96+
0
// \ _ - / \\
:o: 3.5 “—‘—’ :o: :0:

Figure 1.5 Resonance Structure of Ozone

Overall, ozone is a neutral but polar molecule. The high electronegativity of
oxygen makes ozone a powerful electrophile. In fact, ozone is a much more powerful
oxidizing agent than oxygen. Thus, it undergoes a remarkable reaction with alkenes in
which the C-C double bonds are cleaved. No other oxidizing agent is capable of cleaving
double bonds in such a fast, clean, and selective way to yield carbonyl compounds [30].
Due to its low cost and availability, ozone is one of the most attractive reagents for
carrying out oxidative cleavage of unsaturated fatty materials to give an array of
products. The reaction between ozone and oleﬁnic compounds occurs by the well-known
Criegee mechanism [31]. The mechanism consists of an electrophilic attack of ozone, or
a 1,3-dipolar cycloaddition, at the carbon-carbon double bond, producing1,2,3-
trioxolane. This primary ozonide is a very unstable ﬁve-membered ring structure and
decomposes immediately by selective cleavage of the single C-C bond and one O-O bond
leading to a carbonyl intermediate and the “zwitterion” carbonyl oxide intermediate. The
latter is a very reactive molecule that can react in the following ways: (1) recombines
with the carbonyl intermediate to give the Criegee secondary ozonide, 1,2,4-trioxolane.
In an aqueous medium, this secondary ozonide reacts with water to generate carbonyl

compounds and hydrogen peroxide; (2) reacts with protic solvents to produce

15

hydroperoxides; (3) undergoes chemical reduction in the presence of a metallic reducing

agent, like zinc, and water to yield ketones and aldehydes; (4) reacts with itself to

generate polymeric peroxides; (5) rearranges to form carboxylates. The Criegee

mechanism is depicted in Figure 1.6.

c +
R! \H \ y
Carbonyl
Compound

1,2,4-trioxolane
(Secondary Ozonide)

111.0

  

1,2,3-trioxolane
(Primary Ozonide)

Co; + 3'01 \

:0 :0:
Eli .__. |+

 

 

C C
KH/ \RI H/ \R] J

Carbonyl Oxide -5—> Carboxylates
(Zwitterion) 4

\‘i\
2 Aldehydes,
Ketones

Polymeric
Peroxides

Hydroperoxides

2 Carbonyl Compounds,

H202

Figure 1.6 Criegee Mechanism for the Ozonolysis of the Alkene Functional Group

Commercially, large quantities of ozone are produced in specially engineered

electric-discharge generators. Electric discharge technology is the only convenient and

economical industrial method for ozone synthesis [32]. Figure 1.7 depicts a typical

generator cell, which consists of two metallic electrodes separated by a gas-ﬁlled gap and

a dielectric material. Oxygen gas ﬂows through the discharge gap while high voltage (8-

16

10kV) is applied to the electrodes. Ozone is produced as a direct result of power
dissipation in the generator. The major part of the energy applied during the electrical
discharge is transformed into heat. This heat must be evacuated from the discharge space
to maintain correct ozone generator performance. Thus, cooling water circulates between

the stainless steel dielectric tube and the cooling jacket to dissipate the heat generated.

Water cooled Low Voltage electrode
—

O .
_2_p Discharge space —p

 

High Voltage electrode

Figure 1.7 A Typical Electric Discharge Ozone Generator
Although there are a number of mechanisms that may contribute to ozone

formation in a generator, one particular reaction path is considered dominant [33]. The
reaction is initiated when free, energetic electrons dissociate oxygen molecules:

e' + 02 —-> 20 + e' (1.1)
Following this, ozone is formed by a three-body collision reaction:

0 + 02 ——> 03 (1.2)

At the same time, however, atomic oxygen and electrons also react with ozone to form
oxygen:

0 + O3—> 202 (1.3)

e'+O3 ——> Oz+O+e' (1.4)

17

Ozone-oxygen mixtures are explosive over a wide range of ozone concentrations (~ 20-
100%, vol). Working with ozone at concentrations of 0 to 15% (vol) is considered to be
safe because explosive decomposition of ozone does not occur in this range. However,
because of the competing reaction of ozone decomposing back to oxygen, ozone is
generally synthesized at low concentrations, typically between 2-5% (vol) [34].
1.6 Research Hypothesis

Marshall et al. [35, 36] described experimental ﬁndings on the direct conversion
of certain oleﬁns to methyl esters by treatment with ozone in methanolic sodium
hydroxide or sodium methoxide with dichloromethane as a co-solvent at -78°C. The
results were consistent with a reaction pathway in which the aldehyde and carbonyl oxide
intermediate, derived from the primary ozonide in the Criegee mechanism, react with
methanol to afford hemiacetal and hydroperoxide, respectively. The hemiacetal
undergoes base-assisted hydride abstraction by ozone to produce methyl ester, while
generating oxygen and water as by-products. The hydroperoxide dehydrates, liberating a
water molecule and producing a methyl ester. The reaction mechanism is shown in
Figure 1.8. This reaction scheme has been applied to a number of allylic ethers having
terminal double bonds and to several oleﬁns with internal double bonds. For example,
methyl oleate was converted to a separable mixture of methyl nonanoate and dimethyl

azelate in 78% and 77% yields, respectively.

18

6' 8" ¢—- - +
MeOH +B___.MeO+BH

o V’ﬁ /"
- II 0 + 0
(I)Me0\ + C —-v I + BH __.| + B
/ \
R; H Rz/C\\H Rz/C\\H
OM OM
Carbonyl e 8
Compound Hemiacetal
H
/
0
I‘2 /0\ O
+o/o—-+II +02+HOH
R2 C\ /C\0Me
OMe Ozone R
Ester
_ I 0 0
("”1201 '_’ I + “L" " B
R. H R./C\\H R,/C\\H
Carbonyl OMe OMe
Oxide Methoxy
Hydroperoxide
pm

0
II

R /C\ OMe
I

Ester

Figure 1.8 Mechanism for the Direct Conversion of Olefins to Esters Via Ozonolysis
Source: Ref. [35]

Applying the work of Marshall et al. [35, 36], the oxidative cleavage of a mixture
of alkenes was employed by the ozonolysis of methyl soyate under basic methanolic
conditions. Reaction conditions were chosen based on engineering scale-up
considerations: the reaction temperature was chosen to be room temperature, rather than
~78°C; to minimize toxic waste disposal, dichloromethane, a carcinogen, was not used as

a co-solvent; and for ease of product separation, a heterogeneous catalyst was employed.

l9

The expected products from this reaction are shown in Figure 1.9 and their properties are

listed in Table 1.2. Unlike with the other chemical modiﬁcation techniques described in

the next chapter, it is expected that eliminating the double bonds will enhance the thermal

and oxidative properties of biodiesel. Moreover, a methyl ester functionality at the

terminal position is expected to enhance the cold-ﬂow properties and should prevent

wax-like crystallization and precipitation. The cleavage of the fatty acid residues at the

double bond will lower the molecular weight of biodiesel by generating shorter,

fragmental esters, decreasing its viscosity and increasing its volatility to be comparable to

that of diesel fuel. It is expected that this treatment will negate the need for blending

biodiesel with petroleum-based diesel.

 

 

OMe
WCzo
(PMe O3 Methyl Nonanoate
/\/\/\/\:—/\/\/\/\ : —->
C O MeOH, OMe (I)Me
Methyl Oleate Catalyst O=CWC=O
Dimethyl Azelate
OMe OMe OMe
/\/\/C=O O=C \/C=O
Methyl Hexanoate Dimethyl
(RMC 03 Malonate
/\/\/=\/=\/\/\/\/C:0 "—"'
. MeOH, OMe OMe
Methyl Linoleate Catalyst O‘C (I: O
— W =
Dimethyl Azelate
9M6 OMe OMe
”C =0 2 o=cvc=o
Methyl Propionate Dimethyl
OMe o3 Malonate
/\—_:/\.—_-/\-:/\/\/\/\C =0 —'.‘
, MeOH, (PM? PM:
Methyl Linolenate Catalyst O=CWC=O
Dimethyl Azelate

Figure 1.9 Expected Ester Products from the Ozonolysis of Methyl Soyate

Table 1.2 Properties of the Initial and Expected Product Esters

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The speciﬁc goal of this research study was to chemically modify biodiesel using
ozone chemistry in order to improve its overall fuel quality. To achieve this goal, the
following experiments were conducted on the ozonated biodiesel fuel:

0 Structural characterization (F TIR, NMR, GC, GC/MS): analyzed the product mixture

of the ozonated fuel to monitor the degradation of double bonds and the formation of

Melting Boiling
Methyl Molecular Structure Molecular Point Point
Ester Weight (°C) (°C)
Initial Esters
Methyl /O\r\/\/\/\/\/\N 270 30 136
Palmitate I
0
Methyl /O\‘r\/\M/\MN 298 40 181
Stearate 0
Methyl /OW 296 -20 213
Oleate 0
Methyl /0W 294 -35 215
Linoleate O
Methyl ,oxfrx/xéxAMA/x/ 292 below 1 82
Linolenate -35
0
Expected Product Esters
Methyl / O 88 -88 80
Propionate r
Methyl /O\/\/\/ 130 -71 151
Hexanoate "
O
Methyl / O W 172 -40 214
Nonanoate "
O
Dimethyl ,0 0\ 216 -20 156
Azelate M
Dimethyl /Ow0\ 132 -62 181
Malonate O O
1.7 Speciﬁc Goal & Research Objectives

the expected esters, based on the mechanism proposed by Marshall et al. [3 5].

21

 

0 Thermal characterization (TGA, DSC, Low-Temperature Flow Properties): analyzed
the volatility and oxidative stability of the ozonated fuel; measured key low-
temperature properties, including cloud point, pour point, cold ﬁlter plugging point,
onset crystallization temperature, and viscosity.

Biodiesel derived from soybean oil was chosen due to its crop abundance and
availability in the US. Low-saturated (low-sat) biodiesel contains half the amount, by
weight, of the saturated components contained in regular biodiesel. Low-sat biodiesel is
of particular interest due to its reduced saturation level, making it more appealing than
regular biodisel for low-temperature applications. Thus, experiments were conducted
with both low-sat and regular biodiesel fuels for comparative studies.

1.8 Organization of Dissertation

This dissertation is divided into six chapters. The current chapter explains the
signiﬁcance of this work, provides background information on vegetable oil chemistry,
biodiesel research, and ozone chemistry; and states the problem to be investigated and the
proposed solution to solve it. Chapter 2 reviews the four common chemical modiﬁcation
techniques- pyrolysis, dilution, microemulsion, transesteriﬁcation- used to improved
biodiesel fuel quality. Chapter 3 explains the analytical techniques used in this work,
including a brief description of the theory of operation and the experimental parameters
used. Chapters 4 and 5 provide the experimental results and detailed discussions on the
structural and thermal characterization of ozonated biodiesel fuel, respectively. Finally,

Chapter 6 reviews the major experimental ﬁndings, gives recommendations for future

work, and provides other considerations relating to biodiesel research.

22

Chapter 2
Literature Review

There have been many problems associated with using neat vegetable oil in diesel
engines, including (1) coking and trumpet formation on injectors to such an extent that
fuel atomization does not occur properly or is even prevented as a result of plugged
oriﬁces, (2) carbon deposits, (3) oil ring sticking, and (4) thickening and gelling of the
lubricating oil as a result of contamination by vegetable oils [37]. Other major
disadvantages include their high viscosity, causing poor ﬂow and atomization
characteristics within diesel engines. Furthermore, vegetable oils solidify at intermediate
temperatures, which is impractical for low-temperature use and applications. Four
chemical/physical modiﬁcation techniques have been investigated towards solving these
challenging problems, including pyrolysis, dilution, microemulsion, and
transesteriﬁcation. This chapter reviews the fuel preparation of neat vegetable oils by
these four processes and their effect on fuel properties and engine performance.
2.1 Pyrolysis

Pyrolysis, or thermal cracking, is the catalytic thermal decomposition of vegetable
oil at high temperatures (300-800°C) in the absence of air. This process involves
cleavage of C-C chemical bonds to yield smaller molecules of all possible fragments,
including alkanes (parafﬁns), alkenes (oleﬁns), alkadienes, carboxylic acids, aromatics
and small amounts of gaseous products, to achieve high yields of liquid fuels. The
pyrolyzed material can be vegetable oils, animal fats, natural fatty acids, and methyl
esters of fatty acids [37]. In most research studies, the pyrolysis of vegetable oil use

metallic salts as catalysts to obtain products structurally similar to those present in

23

petroleum sources. Thermal cracking of fats and oils has been investigated for more than
100 years, especially in countries where there is a shortage of petroleum deposits [3 8]. In
1888, the ﬁrst pyrolysis of vegetable oil was conducted by Engler in an attempt to
synthesize petroleum from vegetable oil [39]. Since World War 1, many researchers [29,
40-49] have studied the thermal cracking of vegetable oils to obtain products suitable for
fuel, using different reaction conditions and methods.

Schwab et al. [40] thermally decomposed reﬁned soybean oil using the ASTM
standard method for distillation of petroleum products. Typical breakdown of the
distillates found from the pyrolysis of safflower and soybean oil using GC/MS analysis is
listed in Table 2.1. The carbon-hydrogen ratio in the distillates showed about 79% and
12%, respectively, indicating considerable amounts of oxygenated compounds.

Table 2.1 Compositional Data of Pyrolyzed Oils“

 

 

 

 

Percent by Weight

High Oleic Safflower Oil Soybean Oil

N2 Sparge Air N2 Sparge Air
Alkanes 37.5 40.9 31.3 29.9
Alkenes 22.2 22.0 28.3 24.9
Alkadienes 8.1 13.0 9.4 10.9
Aromatics 2.3 2.2 2.3 1.9
Unresolved Unsaturates 9.7 10.1 5.5 5.1
Carboxylic acids 11.5 16.1 12.2 9.6
Unidentiﬁed 8.7 12.7 10.9 12.6

 

“Source: Ref. [40]

The fuel properties of the pyrolyzed soybean oil were improved substantially compared
to the unpyrolyzed soybean oil. The cetane number of the pyrolyzed soybean oil was
enhanced to 43 from 37.9, exceeding the ASTM minimum value of 40. The viscosity
was reduced from 32.6 cSt to 10.2 cSt, a two-thirds reduction, but still exceeded the

ASTM speciﬁed value of 7.5 cSt. The pyrolyzed vegetable oil had acceptable amounts of

24

water and sediment, sulfur and copper corrosion values; but unacceptable ash, carbon
residue amounts and pour point. Niehaus et al. [50] also thermally cracked reﬁned
soybean oil and obtained similar fuel properties. The fuel properties of thermally cracked
soybean oil are compared with the fuel properties of neat soybean oil and No. 2 diesel
fuel in Table 2.2.

Table 2.2 Comparative Fuel Properties of Soybean Oil and Diesel Fuel

 

 

 

 

 

Soybean Oil Crach No. 2 Diesel Fuel
Soybean Oil
a b a b a b
Viscosity, cSt, 38°C 32.6 32.6 10.2 7.74 1.9-4.1 2.82
Pour Point, °C +12 +12.2 +7 +4.4 -7 max. -6.7 max.
Cetane Number 37.9 38.0 43.0 43.0 40.0 51.0
Higher Heating 39.6 39.3 40.3 40.6 45.5 45.6

Value, MJ/kg
“Source: Ref [40], I’Source: Ref. [50]

 

Catalytic cracking of two tropical vegetable oils, copra and palm oils, at 450°C
over a SiOz/Ale3 catalyst to produce liquid biofuels with lower molecular weights has
also been studied [51]. The chemical composition and physical properties of the
thermally cracked vegetable oil ﬁ'actions were close to that of fossil fuel. However, the
formation of water, coke and tar made up about 15 wt% of the pyrolyzed products.

Dandik and Aksoy [42, 52, 53] performed a series of studies in the pyrolysis of
used vegetable oil using a fractionating pyrolysis reactor equipped with a packed column.
They studied the effects of reaction temperature (400°C and 420°C), catalyst type
(sodium carbonate and HZSM-S), catalyst amount (1, 5, 10, and 20 wt% of the oil mass)
and column length (180, 360 and 540 mm) on the thermal cracking of vegetable oils. In
all three studies, conversion was found to increase with an increase in reaction

temperature and decrease with an increase in the column length. Moreover, an increase

25

in the reaction temperature increased the amount of acid phase, liquid hydrocarbons, and
gaseous products but decreased the amount of aqueous phase. Also, an increase in the
column length decreased the amount of liquid hydrocarbons and acid phase and increased
the amount of coke-residual oil. An increase in both catalyst content and temperature
increased the formation of both liquid hydrocarbons and gaseous products and decreased
the formation of the aqueous phase, acid phase, and coke-residual oil. The reaction
products leaving the fractionating column were separated into liquid (organic and
aqueous phases) and gaseous fractions, which were analyzed by gas chromatography. In
all three investigations, the pyrolyzed oil consisted of gaseous and liquid hydrocarbons,
carboxylic acids, C0, C02, H2, water, and coke. The liquid hydrocarbon fraction
consisted mainly of alkanes, alkenes and their isomers, and aromatics. The gaseous
ﬁaction contained C0, C02, H2, and saturated/unsaturated hydrocarbons mostly in the
C1-C3 range. Depending upon the experimental conditions, coke-residual oil made up
between 4-60 wt% of the product composition.

The pyrolysis of a mixture of methyl esters derived from rapeseed oil, called
methyl colzate, was studied in a tubular reactor between 550 and 850°C [54]. The major
products were oleﬁns, paraffms, aromatics and saturated/unsaturated methyl esters. The
effect of temperature on conversion was studied and it was observed that the amount of
methyl colzate converted at 550°C was about 6 wt% and increased nonlinearly up to
850°C. Starting at 750°C, conversion increased more slowly as it approached 100 wt%,
with 96.6 wt% conversion at 850°C. Coke was a minor by-product and its amount of

formation seemed to be independent of temperature. Other research studies [41, 55-5 7]

26

on the pyrolysis of methyl esters produced the hydrocarbons normally produced in
conventional diesel fuel.

Mechanisms for the thermal decomposition of triglycerides are complex because
of the many structures and multiplicity of possible reactions of mixed triglycerides. In
general, thermal decomposition of these molecules proceeds through either a free-radical
or carbonium ion mechanism [47, 58]. Alencar [47] proposed a scheme for the thermal
decomposition pathway of saturated moieties of triglycerides during pyrolysis, which
follows the Rice free-radical theory modiﬁed by Kossiakoff and referred to as the RK
theory [59]. Carboxylic acids formed during pyrolysis is most likely a result from the
cleavage of the glyceride moiety, as suggested by Nawar [41].

Very little research has been conducted on diesel engine combustion of pyrolyzed
oils. To investigate their ignition delay and combustion behavior, Shihadeh and
Hochgreb [60] conducted experiments with two biomass pyrolyzed oils and No. 2 diesel
fuel in a direct injection diesel engine. If was found that while the indicated thermal
efﬁciency of both pyrolysis oils equaled that of diesel fuel, they exhibited excessive
ignition delays. The longer ignition delay time observed was associated with the
chemical composition of the pyrolyzed fuel. Also, neither pyrolyzed oil could ignite
without a moderate degree of combustion air preheating at 55°C. Niehaus et a1. [50]
tested thermally cracked soybean oil on a diesel engine. The oil produced slightly less
power than diesel fuel and produced lower levels of nitrogen oxide and higher levels of
hydrocarbons than diesel fuel. The engine testing was limited to short-term tests.

The equipment for pyrolysis is expensive for modest throughputs and this thermal

cracking process consumes a lot of energy due to high reaction temperatures. Although

27

the products are chemically similar to petroleum-derived gasoline and diesel fuel, the
removal of oxygen during the thermal processing also removes any environmental
beneﬁts of using an oxygenated fuel [37]. Pyrolyzed oils contain signiﬁcant quantities of
moisture (~15-25 wt%), particulates, nitrogen, alkali, and tar, and are generally more
dense and viscous than No. 2 diesel ﬁrel [60].
2.2 Dilution

Dilution or blending is simply mixing diesel fuel with vegetable oil. Numerous
performance tests in a diesel engine for various diesel/vegetable blends have been
researched. A long-term performance test was conducted on a 3:1 (vol) fuel blend of
unreﬁned mechanically expelled soybean oil and diesel fuel, respectively [61]. The
viscosity of the expelled soybean oil was about 13.5 times as viscous as diesel fuel at
40°C. By blending it with 25 vol% diesel fuel, the viscosity was reduced by half.
However, this blended viscosity was still 7.3 times as viscous as diesel fuel at 40°C. The
ZOO-hr screening test for alternative fuels set forth by the Engine Manufacturer’s
Association (EMA) was used to evaluate the performance of the test engine when
burning the blended fuel. A test failure occurred 90-hr into the screening test due to a
dramatic 670% increase in the lubricating oil viscosity. After the oil was changed, the
test was allowed to continue to see if any further deterioration occurred. At the 159-hr
point, the engine no longer maintained a constant load and the screening test was
terminated. After the testing, abnormal carbon buildup/deposits and wet, gummy
substances were found on all injector tips and all the engine parts of the combustion

chamber. Schlick et al. [62] conducted the same EMA engine testing on mechanically

28

expelled, unreﬁned soybean oil blended with No. 2 diesel fuel in a 3:1 volume ratio and
observed similar results.

In a paper by Adams et al. [63], mixtures of degummed soybean oil with No. 2
diesel fuel in the volume ratios of 1 :2 and 1:1, respectively, were tested for engine
performance and crankcase lubricant viscosity in a John Deere 6-cylinder, direct-
injection engine. The 200-hr EMA engine testing was conducted on both sets of blends.
The results indicated that a lubricating oil contamination problem resulting in an
unacceptable thickening and a potential for gelling occurred with the 1:1 blend.
Moreover, the results of a 400-hr endurance run on the 1:2 blend showed that carbon
deposits accumulated on the injector tips, intake valves, pistons, and the exhaust area.

Other vegetable oil blends with diesel fuel have also been studied. Ziejewski et
al. [8] studied the effects of using a 1:3 (vol) blend of alkali-reﬁned sunﬂower oil and
diesel fuel in a direct-injection diesel engine and compared its engine performance with
non-blended diesel fuel. The viscosity of the blended fuel was reported to be 4.88 cSt at
40°C, moderately less than that of the neat sunﬂower oil; but still above the maximum
speciﬁed ASTM value of 4.0 cSt at 40°C. Problems such as early deterioration of
injection nozzle performance, piston ring groove carbon ﬁlling, heavy carbon on the
piston lands, and heavy carbon build-up on the cylinder liners were observed. These
problems would result in premature engine failure. Thus, the 1:3 fuel blend was not
recommended for long-term use in a direct-injected diesel engine. A comparable blend
with high-Oleic safﬂower, replacing sunﬂower oil, had a viscosity of 4.92 cSt at 40°C and
passed the 200-hr EMA test [64]. The different results were attributed to the degree of

unsaturation of the vegetable oil. The more unsaturated oil is highly reactive and tends to

29

oxidize and polymerize, and the accumulation of such products leads to thickening of the
lubricant. Thus, frequent replacement or change of the lubricant oil becomes necessary.

Direct use of vegetable oils and/or the use of blends of the oils has generally been
considered to be unsatisfactory and impractical for both direct and indirect diesel engines
[3 7]. The high viscosity, acid composition, free fatty acid content, carbon deposits and
lubricating oil thickening, as well as gum formation due to oxidation and polymerization
during storage and combustion, are all challenging problems.

2.3 Microemulsion

Microemulsiﬁcation was amongst the ﬁrst solutions pursued to solve the high
viscosity problem of vegetable oils [65]. Schwab and Pryde [66] deﬁned a
microemulsion as a colloidal equilibrium dispersion of optically isotropic ﬂuid
microstructures with dimensions generally in the 1 to 150 nm range formed
spontaneously from two normally immiscible liquids and one or more amphiphile. They
can be composed of diesel fuel, vegetable oil, an alcohol, a surfactant, and a co-
surfactant. Microemulsions can be classiﬁed as nonionic or ionic, usually depending on
the arnphiphile or surfactant present. Microemulsions with solvents, such as methanol,
ethanol, l-butanol and ionic or non-ionic surfactants, have been studied.

Hybrid fuels based on vegetable oils without combination with conventional
diesel fuel are among the most widely studied formulations [24]. Hybrid fuels of special
interest are water-in-oil type microemulsions in which the vegetable oil is the continuous
phase and an aqueous alcoholic solvent forms the dispersed phase [67]. For example,
Ziejewski and Kaufman [8] prepared a nonionic sunﬂower oil-aqueous ethanol

microemulsion composed of 53.3 vol% alkali-reﬁned, winterized sunﬂower oil, 13.3

30

vol% ethanol and 33.4 vol% l-butanol. This nonionic emulsion was characterized by a
viscosity of 6.31 cSt at 40°C, cetane number of 25, and had an ash content of less than
0.01 wt%. These and other fuel properties are listed in Table 2.3. In a EMA 200-hr
screening test, no signiﬁcant deterioration in performance was observed; however, heavy
carbon deposits, premature injection-nozzle deterioration (irregular needle sticking),
incomplete combustion, and an increase of the lubricating oil viscosity were all problems
experienced while operating with the microemulsion. Therefore, the tested
microemulsion was not recommended for long-term use in a direct-injection diesel
engine.

Goering and Fry [68] used soybean oil instead of sunﬂower oil in a
microemulsion. The nonionic fuel was composed of 50 vol% No. 2 diesel fuel, 25 vol%
degummed, alkali-reﬁned soybean oil, 5 vol% ethanol, and 20 vol% l-butanol. The fuel
properties are also summarized in Table 2.3. Both the hybrid fuel and No. 2 diesel fuel
completed the engine screening test without difﬁculty; but the hybrid burned more
efﬁciently over the entire speed range. Furthermore, no substantial changes were
observed in the viscosity of the lubricating oil when bunting either No. 2 diesel or hybrid
fuels. The better performance can be attributed to the solvent action and cooling effect of
the alcohol in keeping the injector needles and oriﬁces clean. Similar results were also

reported by Goering [67] in the study of two (ionic and nonionic) hybrid fuels.

31

Table 2.3 Fuel Properties of Microemulsions

 

 

Property No. 2 Nonionic Shipp Hybrid F uelsc

Diesel Sunﬂower Oil- Nonionic

F uel" Aqueous Ethanol” F 11er

Logig Nonionic

Viscosity, cSt, 40°C 2.37 6.31 4.03 8.77 6.77
Pour Point, °C -29 0* -- c* 6*
Cetane Number 50.] 25 34.7 29.8 25.1
Flash Point, °C 51.7 min.‘ 27 28.3 22.2 27.8
Heat of Combustion 45, 422 36, 393 41 -- --
IKJ/kg)

 

“Source: Ref. [8], “I The sample separated into two phases at 2°C. The lower layer
solidiﬁed at —29°C and the upper layer was still liquid at —65.0°C; bSource: Ref. [68];
Source: Ref. [67], c The fuel separated into two layers at 0°C.

In a paper by Masjuki et al. [69], engine evaluation was conducted on a diesel
engine ﬁreled with emulsions of Malaysian palm oil diesel or conventional diesel,
containing 5% and 10% of water by volume, to determine the engine performance and
wear characteristics. If was found that palm oil diesel emulsiﬁed with water did not
present any obstacles in the operation of diesel engine during steady state engine tests. In
fact, the main conclusion was that the engine performance and fuel consumption for palm
oil diesel and its emulsions were comparable with those of conventional diesel fuel.

To select candidate fuels, potential formulations are characterized by physical
characteristics such as phase equilibrium and miscibility limits [29]. Schwab et al. [29]
used the ternary phase equilibrium diagram and the plot of viscosity versus solvent
fraction to determine the emulsiﬁed fuel formulations. All microemulsions with butanol,
hexanol and octanol met the maximum viscosity requirements for No. 2 diesel. Mixtures
of hexadecane, l-butanol and 95 wt% ethanol also formed microemulsions [70].
Furthermore, Schwab and Pryde [66] demonstrated the use of 2-octanol as an effective

surfactant in the micellar solubilization of methanol in triolein and soybean oil. Thus, by

32

microemulsion formation, it is possible to prepare alternative diesel fuels completely free
of petroleum.
2.4 Transesteriﬁcation

Transesteriﬁcation, also called alcoholysis, is a reversible reaction of fats or oils
with alcohol to form alkyl esters and glycerol. This process is by far the most common
method for reducing the viscosity of vegetable oils. The general scheme of the
transesteriﬁcation reaction is shown in Figure 2.1. According to the chemical equation,
the stoichiometry of this reaction requires a 3:1 molar ratio of alcohol to triglyceride to
produce 1 mole of glycerol and 3 moles of fatty acid alkyl esters. Moreover, the
molecular weight of an ester molecule is roughly one-third that of its parent vegetable oil
molecule and has a viscosity approximately twice that of diesel fuel instead of 10 to 20
times, as is the case for the neat vegetable oils [71]. The most commonly prepared esters
are methyl esters, largely because methanol is the least expensive alcohol. It has been
reported the yield of alcohol esters was the highest for methanol, as methanol is the
shortest-chain alcohol and more reactive, with the added advantage of alkaline catalysts

being easily soluble in it because of its polarity [3 8].

 

 

(I? o
CHz—O—C-Rl R’-O-g-R1 CHz—OH
0
ll Catalyst H
CH —O—C—R2 + 3 R’OH : R’—O-—C-R3 + CH —OH
I? if
CH2—0—C—R3 R’—0—C—R2 CH2-0H
Vegetable Oil Alcohol Fatty Acid Glycerol
Alkyl Esters

Figure 2.1 Transesterification Reaction of Vegetable Oil

33

The transesteriﬁcation of various animal fats, oils and waste oils has been
extensively studied for the past 20 twenty years, particularly in the 1980’s. In fact,
several reviews concerning the production of biodiesel by transesteriﬁcation have been
published [3 7, 72-79]. The main factors inﬂuencing the yield and purity of biodiesel
include purity of the feedstocks, alcohol/vegetable oil molar ratio, catalyst type, reaction
time, reaction temperature, and mixing.

2.4.1 Mechanism & Kinetics

Transesteriﬁcation consists of a number of consecutive, reversible reactions [29,
80]. Thus, a catalyst and excess alcohol are used to increase the rate of reaction and to
shift the equilibrium to the right, respectively. As depicted in Figure 2.2, the triglyceride
is converted stepwise to diglyceride, monoglyceride, and ﬁnally to glycerol. A mole of
ester is liberated at each step. The mechanism of base-catalyzed transesteriﬁcation of
vegetable oils is illustrated in Figure 2.3. The mechanism was formulated as four steps
[81, 82]. The ﬁrst step is the reaction of the base with the alcohol, producing an alkoxide
and the protonated catalyst (A). The nucleophilic attack of the alkoxide at the carbonyl
group of the triglyceride generates a tetrahedral intermediate (B), from which the alkyl
ester and the corresponding anion of the diglyceride are formed (C). The latter
deprotonates the catalyst, thus regenerating the active species (D), which is able to react
with a second molecule of the alcohol, starting another catalytic cycle. Diglycerides and
monoglycerides are converted by the same mechanism to a mixture of alkyl esters and
glycerol. The mechanism of an acid-catalyzed transesteriﬁcation is similar in that the
tetrahedral intermediate is formed. However, carboxylic acids can be formed by the

reaction of a carbocation intermediate with water present in the reaction mixture. This

34

suggests that an acid-catalyzed transesteriﬁcation should be carried out in the absence of
water, in order to avoid the competitive formation of carboxylic acids which reduces the

yield of alkyl esters.

0
Catalyst ||
1. Triglyceride (TG) + R’OH +——' Diglyceride (DG) R’— 0 - C — R,

0
Catalyst II
2. Diglyceride (DG) + R’OH : Monoglyceride (MG) R’— 0 — C — R2

0
Catalyst ||
3. Monoglyceride (DG) + R’OH +—' Glycerol (GL) R’— 0 - C — K;

Figure 2.2 Stepwise Conversion of Glycerides to Esters

ROH + B —*, R0 + BH (A)
mcoo ‘FHZ _ RICOO—CH2
R2COO—FH + 0R ,._—* R2C00—CH OIR
I
Hzc-Olf-Ra H2C—0-(|3-R3 (B)
o 0'
RICOO—CH2 I Rlcoo-CH2
4.—
R2000—CH OIR R2COO—CH + Roocng, (C)
H2C-O—C—R3 H2C—O-
I 3::
o
RICOO—CH2 RICOO—CH2

+ _
R2COO—FH + BH 2132000 CH + B (D)

Figure 2.3 Mechanism of Base-Catalyzed Transesterification of Vegetable Oils
Source: Adopted from Ref. [77]

35

Surprisingly, little is known about the kinetics of the transesteriﬁcation of
vegetable oils. The reason might be the complexity of the reaction itself, which runs
through two intermediates, in addition to the analytical problem in simultaneously
quantifying mono-, di-, and triglycerides as well as methyl esters [83]. Freedman et al.
[80] were one of the ﬁrst researchers to study the transesteriﬁcation kinetics of soybean
oil. With acid or alkaline catalysis, the forward reaction followed pseudo-ﬁrst-order
kinetics for a 30:1 molar ratio of butanolzsoybean oil. However, for a molar ratio of 6:1
in the alkaline-catalyzed study only, the forward reaction followed consecutive second-
order kinetics. The reaction kinetics of methanol with soybean oil at a 6:1 molar ratio
with 0.5% (w/w) sodium methoxide at 20-60°C was a combination of second-order
consecutive and fourth-order shunt reactions. A shunt reaction is a reaction in which all
three positions of the triglyceride react virtually simultaneously to give three alkyl ester
molecules and glycerol. Reverse reactions of both acid and alkaline catalysis appeared to
be second-order. For both forward and reverse reactions, the rate constants for the
alkaline-catalyzed reactions were signiﬁcantly larger than those for the acid-catalyzed
reactions. Also, the rate constant increased with an increase in the amount of catalyst
used.

The transesteriﬁcation kinetics of soybean oil with methanol was also investigated
by Noureddini et al. [84]. The effect of mixing and temperature on the reaction rate was
studied while the molar ratio of alcohol to oil and concentration of catalyst were held
constant. The experimental results revealed that the effect of mixing is most signiﬁcant
during the slow rate region of the reaction. As methyl esters are formed, a single phase is

established and mixing became insigniﬁcant while the reaction temperature primarily

36

inﬂuenced the reaction rate. Thus, the experimental results clearly demonstrated an
initial mass transfer-controlled region, followed by a kinetic-controlled region. The data
for the latter region ﬁtted well into a second-order kinetic mechanism.
2.4.2 Effects of Moisture & Free Fatty Acids

Wright et al. [85] noted that the starting materials used for alkaline-catalyzed
transesteriﬁcation of vegetable oils must meet certain speciﬁcations. The triglyceride
should have an acid value less than 1 and all materials should be anhydrous. If the acid
value is greater than 1, more sodium hydroxide is required to neutralize the free fatty
acids, which results in the production of soap. Water can also cause soap formation,
which consumes the catalyst and reduces its efﬁciency. The resulting soaps cause an
increase in viscosity or formation of gel, lower the yield of ester, and the separation of
ester and glycerol during water washing becomes difficult. As little as 0.3% water in the
reaction mixture reduces ester yields by catalyst consumption [86]. Other researchers
have also stressed the importance of oils being dry and free of free fatty acids [87, 88].
Freedman et al. [86] also reported that ester yields were signiﬁcantly reduced if the
reactants did not meet these speciﬁcations. In his study, prolonged contact with air
diminished the effectiveness of both sodium hydroxide and sodium methoxide through
interaction with moisture and carbon dioxides. In the presence of water or moisture, the
esters produced from transesteriﬁcation can undergo saponiﬁcation to produce fatty salts,
also referred to as soap, as depicted in Figure 2.4. While, shown in Figure 2.5, hydrolysis
of the triglyceride can occur to produce free fatty acids. These free fatty acids, and the
free fatty acids originally present in the vegetable oil, can undergo further chemical

reaction via saponiﬁcation generating additional water, illustrated in Figure 2.6. Thus,

37

the absence of moisture and free fatty acids in the vegetable is important in order to

maximize product yield and enhance product purity.

0 0
Water II - +
R—C—OR’ + NaOH —> R—C—O Na + R’OH
Ester Metallic Salt Simple
Alkoxide Alcohol

Figure 2.4 Saponiﬁcation of Ester

j.) ‘i
CHz—C—o-RI OH—C‘R' CH2—OH
| 0 0 I
+ Heat II
CH-C—O-Rz 3H20 —o OH_C_R2 + CH-OH
I ° |
|| 0
CH2—C—O—R3 II CH2—OH
OH—C—m

Figure 2.5 Hydrolysis of Triglyceride

0 0
II Heat II - +
R—C—OH + NaOH —' R-C—O Na + H20
Free Fatty Acid Metallic Salt Water
Alkoxide

Figure 2.6 Saponiﬁcation of Free Fatty Acid

The effects of free fatty acids and water on transesteriﬁcation of beef tallow with
methanol were investigated [89]. This study reported that the presence of both free fatty
acids and water had a synergistic negative effect on the reaction. Thus, in order to obtain
maximum conversion, the water content of beef tallow should be kept below 0.06%
(w/w) and the free fatty acid content should be kept below 0.5% (w/w). This maximum
content of free fatty acids conﬁrmed the research results of Bradshaw and Meuly [88] and

Feuge and Grose[87].

38

2.4.3 Effect of Molar Ratio

One of the most important variables affecting the yield of ester is the molar ratio
of alcohol to triglyceride [3 7]. Stoichiometrically, transesteriﬁcation of vegetable oil
requires three moles of alcohol and one mole of triglyceride to produce three moles of
fatty acid ester and one mole of glycerol. Based on the Le Chatelier’s principle, excess
amount of alcohol is generally used to shift the reaction equilibrium far to the right.

Thus, high alcohol to vegetable molar ratios result in greater ester conversion than the
stoichiometric molar amounts.

Bradshaw and Meuly [88] stated that a molar ratio of 4.8:] of methanol to
vegetable oil led to an ester yield of 97-98%, depending on the quality of the oil. They
also noted that a molar ratio greater than 5.25:1 interfered with the gravitational
separation of glycerol and added more cost to the separation process due to the excess
amount of residual alcohol. Freedman et al. [86] studied the effect of molar ratio on ester
conversion with four vegetable oils. Soybean, sunﬂower, peanut, and cottonseed oils
behaved similarly and achieved highest conversions to esters (93-98%) at the 6:1 molar
ratio. It was also noted that ratios greater than 6:1 did not increase yields, but rather
complicated ester and glycerol recovery and increased the cost of alcohol recovery. In
the ethanolysis of peanut oil, a 6:1 molar ratio liberated signiﬁcantly more glycerol than a
3:1 molar ratio [87]. In the transesteriﬁcation of cynara cardunculus L. oil, molar ratios
of ethanol to cynara were studied [90]. With a stoichiometric amount of alcohol, the
conversion to esters was about 62% after 2 hours. The ester yields increased as the molar
ratio increased up to a value of 12:1. The best results were for molar ratios between 9:1

and 12: 1. For molar ratios less than 6: l , the reaction was incomplete; and for a molar

39

ratio of 15:1, the separation of glycerol was difﬁcult and the apparent yield of esters
decreased because part of the glycerol remained in the biodiesel phase. Tanaka et al.
[91], in his novel two-step transesteriﬁcation of oils and fats such as tallow, coconut oil
and palm oil, used 6:1-30:1 molar ratios with alkali-catalysis to achieve a conversion of
99.5%.
2.4.4 Effect of Catalyst Type

Catalysis commonly used in the transesteriﬁcation of vegetable oil are alkaline
and acid. The effectiveness of the catalyst is determined by the molar ratio of the
reactants and the quality of the vegetable oil. Alkaline metal alkoxides are the most
effective alcoholysis catalysts because they give very high ester yields in short reaction
times at low molar concentrations [92]. However, alkaline metal hydroxides, like sodium
hydroxide, are cheaper and are, thus, a good alternative because they can give the same
high conversions of vegetable oils just by increasing the catalyst concentration to 1 or
2%, based on the mass of the oil. For acid-catalysis, the acids that can be used include
sulfuric, phosphoric, hydrochloric or organic sulfonic acids. Transmethylations occur
approximately 4000 times faster in the presence of an alkaline catalyst than those
catalyzed by the same amount of acidic catalyst [93]. Even at ambient temperatures, the
alkaline-catalyzed reactions proceeds rapidly, whereas acid-catalyzed reactions
commonly require reaction temperatures above 100°C [82]. Because alkaline catalysts
are less corrosive to industrial equipment than acid catalysts and the reaction rate is
signiﬁcantly faster, most commercial transesteriﬁcations are conducted with this type of

catalysis. However, if the vegetable oil has a high free fatty acid and water content, an

40

acid-catalyzed pre-treatrnent is employed because free fatty acids deactivate an alkaline
catalyst.

The catalysts sodium hydroxide (NaOH) and sodium methoxide (NaOCH3) were
compared at a 6:1 and 3:1 molar ratio of methanol to vegetable oil [86]. Ester conversion
at a 6:1 molar ratio for 1% (w/w) sodium hydroxide and 0.5% (w/w) sodium methoxide
were essentially identical after 60 minutes. However, at the 3:1 molar ratio, the
methoxide catalyst was superior to the hydroxide catalyst during the entire 60-minute
reaction time. Ma et al. [89] noticed that, comparing these catalysts for the methanolysis
of beef tallow, sodium hydroxide was signiﬁcantly better than sodium methoxide.
Maximum yields with 0.3% (w/w) sodium hydroxide and 0.5% (w/w) sodium methoxide
were 60% and 54%, respectively. Encinar et al. [90] studied the ethanolysis of cynara
cardunculus L. oil, by comparing the effectiveness of sodium hydroxide and potassium
hydroxide in a concentration range of 0.25 to 1.5% (w/w). Of these two catalysts,
sodium hydroxide gave a slightly high ethyl ester yield. The optimum concentration for
both catalysts was 1% (w/w), resulting in a conversion of >90%.

The acid-catalyzed transesteriﬁcation of soybean oil with methanol, ethanol, and
butanol were compared using 1% (w/w ) concentrated sulfuric acid [86]. Conversions to
esters were unsatisfactory with both 6:1 and 20:1 molar ratios at 3 and 18 hours,
respectively. Instead, a 30:1 molar ratio resulted in a high conversion to the methyl ester.
However, at this particular ratio, the hours needed to obtain high a conversion were 3, 22,
and 69, for the butyl, ethyl and methyl esters, respectively. Ikwaguagwu et al. [94]
transesteriﬁed palm oil with 3% sulfuric acid at a 23:1 molar ratio of sulfuric acid to palm

oil, which gave a maximum yield of 78% methyl esters.

41

2.4.5 Effect of Reaction Time

Ma et al. [89] studied the effect of reaction time on the transesteriﬁcation of beef
tallow with methanol and 0.3% (w/w) sodium hydroxide as the catalyst. From 1 to 5
minutes, the apparent yield surged from 1% to 38%. Then, the production of beef tallow
methyl ester slowed down and reached a maximum value at about 15 minutes. The initial
delay was due to the mixing and dispersion of methanol into beef tallow. Freedman et a1.
[86] transesteriﬁed peanut, cottonseed, sunﬂower and soybean oils at a 6:1 molar ratio
and in the presence of 0.5% (w/w) sodium methoxide at 60°C. For soybean and
sunﬂower oils, an approximate yield of 80% was observed after 1 minute; similar to the
results of the ethanolysis of peanut oil, in which about 80% of the esters were formed in
the ﬁrst ﬁve minutes [87]. However, ester conversions after 1 minute with peanut and
cottonseed oils were distinctly lower. After 1 hour, the conversions were almost the same
for all four oils, 93-98%.
2.4.6 Effect of Temperature

The rate of reaction is strongly inﬂuenced by the reaction temperature. Generally,
transesteriﬁcation is conducted near the boiling point of the alcohol at atmospheric
pressure, although the reaction may be carried out at room temperature. Given enough
time, transesteriﬁcation can proceed satisfactorily at ambient temperatures in the case of
alkaline catalysis. The methanolysis of reﬁned soybean oil at 60°C, 45°C and 32°C was
studied at a 6:1 methanol/soybean oil molar ratio and using 1% (w/w) sodium hydroxide
[86]. After 0.10 hr, the ester yields at 60°C, 45°C, and 32°C were 94, 87 and 64%,
respectively, showing the inﬂuence of temperature on ester conversion. After 1 hour,

ester formation was identical for the 60°C and 45°C runs, and only slightly lower for the

42

32°C rtm. After 4 hours, the ester conversion for the 32°C experiment slightly exceeded
that of the other two reaction temperatures. A study by Kusy [95] showed similar results,
using temperatures from 32°C to 83°C. It was concluded from both of these papers that a
time of 1 hour at 60°C was equivalent to 4 hours at 32°C in terms of ester conversion
efﬁciency. Encinar et al. [90] studied the ethanolysis of reﬁned cynara cardunculus oil at
75°C, 50°C, and 25°C. In all experiments, an ethanol/oil molar ratio of 9:1 and 1%
(w/w) sodium hydroxide were used. Aﬁer 2 minutes, esters present in the 75°, 50° and
25°C runs were 79%, 76.5%, and 75.5%, respectively. However, after 2 hours, ester
formation was basically identical for the three runs at 93.1%, 92.5%, and 91.6%,
respectively.
2.4.7 Effect of Mixing

A factor of particular importance in the transesteriﬁcation process is the degree of
mixing between the alcohol and triglyceride phases. Triglyceride and alcohol phases are
not miscible and initially form two liquid layers. This miscibility phenomenon results in
a lag time in the formation of methyl esters. Thus, mixing is normally applied to increase
the contact between the reactants, resulting in an increase in mass-transfer rate. The
effect of mixing on the rate of reaction was studied by Noureddini [84]. It was
discovered that the reaction was initially controlled by diffusion, in which poor diﬁusion
between the phases resulted in a slow rate. As methyl esters formed, they acted as a
mutual solvent for the reactants and a single-phase system was formed. The mixing
effect was most signiﬁcant during the slow rate region of the reaction. As the single
phase was established, mixing became insigniﬁcant and the reaction temperature

primarily inﬂuenced the reaction rate. Boocock et al. [96, 97] have addressed the

43

problem of the mass-transfer limitations by the use of non-reactive co-solvents, like
simple ethers.
2.4.8 Engine Performance

Clark et al. [98] burned methyl and ethyl soybean esters in a direct-injection,
turbocharged diesel engine. They found that engine performance during the EMA ZOO-hr
test with the soybean esters did not differ greatly from that of diesel fuel. Emissions for
both methyl and ethyl esters, as well as No. 2 diesel fuel, were essentially the same.
Hydrocarbon emissions from the esters were slightly less than those from No. 2 diesel
fuel while NOx emissions were slightly greater for the esters. Measurements of engine
wear and fuel-injection system tests showed no abnormal characteristics for any of the
three fuels after the 200-hr tests. Deposit formation was comparable in amount; however,
the methyl ester engine experienced greater piston carbon deposits. It was also concluded
that the methyl and ethyl esters of vegetable oils could be used as alternative fuels on a
short-term basis, provided certain fuel quality standards are met. Table 2.4 compares fuel
properties of some soybean esters.

Table 2.4 Fuel Properties of Soybean Esters“

 

 

Fuel Viscosity, 40°C Cetane Heat of Cloud Point Pour Point

(mmz/s) No. Combustion (°C) (°C)
(KJ/kg)

Methyl 4.08 46.2 39, 800 2 -1

soyate

Ethyl 4.41 48.2 40, 000 1 -4

soyate

Butyl 5.24 51.7 40, 700 -3 -7

soyate

No. 2 2.07 47.0 45, 343 -15 -33

Diesel Fuel

 

“Source: Refs. [98] and [29]

44

Sims [99] used a tractor powered by a direct-injection engine for evaluating the
performance of tallow ester as an alternative diesel fuel. He concluded that the ﬁrel
properties of methyl tallow esters were remarkably similar to diesel fuel. It was observed
that a blend of diesel fuel and tallow ester gave improved combustion characteristics.

2.5 Summary of the Physicochemical Processes

There has been extensive research in the area of the physicochemical modiﬁcation
of triglycerides for utilization in diesel engines. Each of the four processes discussed
give improved fuel properties over those of unprocessed, neat vegetable oils. However,
the viscosity of chemically modiﬁed vegetable oils is still about twice that of No. 2 diesel
fuel. Moreover, fuel properties, such as low-temperature ﬂow properties and
oxidative/storage properties, are still in need of further enhancement. Thus, alternative
chemical processes must be developed in order to achieve better fuel properties of

vegetable oil-derived fuels and, in turn, their quality as an alternative diesel fuel.

45

Chapter 3
Materials & Methods
3.1 Chemicals

Reﬁned and bleached (RB), regular and low-sat, soybean oils [8001-22-7] were
generously provided by Zeeland Farm Soya (Zeeland, MI). Premium No. 2 diesel fuel
[68334-30-5] was provided by the Michigan State University Service Garage (East
Lansing, MI). High-purity HPLC water [7732-18-5], analytical grade methanol [67-56-
1], petroleum ether [8032-32-4], and potassium iodide [7681-11-0] were purchased from
Mallinckrodt Baker, Inc (Phillipsburg, NJ); sodium hydroxide [1310-73-2] and sodium
sulfate (puriﬁed and anhydrous) [7778-18-9] from Spectrum Quality Products, Inc.
(Gardena, CA); concentrated hydrochloric acid [7647-01-0] from Columbus Chemical
Industries, Inc. (Columbus, WI); and calcium carbonate [471-34-1] from Jade Scientiﬁc
(Canton, MI).

Nine fatty acid methyl ester (FAME) standards used in the quantitative GC
analysis, methyl propionate (propionic acid, methyl ester, [554-12-1]), methyl hexanoate
(hexanoic acid, methyl ester, [106-70-7]), methyl nonanoate (nonanoic acid, methyl ester,
[1731-84-6]), methyl undecanoate (undecanoic acid, methyl ester, [124-10-7]), methyl
palmitate (hexadecanoic acid, methyl ester, [112-39-0]), methyl stearate (octadecanoic
acid, methyl ester, [112-61-8]), methyl oleate (cis-9-octadecenoic acid, methyl ester,
[112-62-9]), methyl linoleate (cis,cis-9,lZ-octadecadienoic acid, methyl ester, [112-63-
0]) and methyl linolenate (cis,cis,cis-9,l2,15-octadecatrienoic acid, methyl ester, [301-
00-8]), were all chromatographically >99% pure and purchased from Nu-Chek Prep, Inc.

(Elysian, MN). Two additional reference standards, dimethyl azelate (nonanedioic acid,

46

dimethyl ester, [1732-10-l]) and dimethyl malonate (propanedioic acid, dimethyl ester,
[108-59-8]), were purchased from TCI America (Portland, OR), each having a 98%
purity. Unless noted, all chemicals were used as received.
3.2 Transesterifcation of Soybean Oil

The transesteriﬁcation reaction was carried out in a 3-neck, 2000-mL capacity,
round-bottom ﬂask, equipped with an adjustable speed mechanical stirrer, condenser,
thermometer, and a heating mantle for temperature—controlled heating. Approximately
850 grams of RB soybean (low-sat or regular) was added to the reaction vessel and pre-
heated to 60°C. To achieve a 9:1 molar ratio of alcohol to vegetable oil, 280 grams of
methanol was premixed with 8.50 grams of sodium hydroxide (1 wt% of the vegetable
oil) and agitated. The methanol/catalyst solution was added to the reaction vessel and the
mechanical stirrer was powered on. The transesteriﬁcation reaction was allowed to
proceed for 2 hours at a reaction temperature of 70°C. The experimental apparatus for
the transesteriﬁcation of RB soybean oil is illustrated in Figure 3.1.

mechanical
stirrer

cooling water out <—— -

condenser
cooling water in —9 =

 

 

 

 

   

thermometer ~ sto”

and vent
heating
mantle

Figure 3.1 Experimental Apparatus for the Transesterification of RB Soybean Oil

47

Once the reaction was complete, the contents of the reaction vessel were
transferred to a 2000-mL capacity glass separatory funnel and allowed to cool to room
temperature. About 35 mL of a 10 M aqueous, concentrated hydrochloric acid solution
was added to neutralize the catalytic base to sodium chloride salt. The aqueous phase
was then discarded and the organic phase was further puriﬁed. Glycerol and excess
methanol were removed by rinsing the organic phase with three cycles of 500 mL of
warm water (~60°C), and the aqueous layer was discarded after each cycle. In order to
completely remove any residual catalyst and glycerol, 1000 mL of petroleum ether was
added and the aqueous layer was again discarded. The resultant solution was dried over
anhydrous sodium sulfate via vacuum ﬁltration. Petroleum ether and residual methanol
in the ester layer were removed on a rotary evaporator under vacuum at 70°C. The ester
product was dried over anhydrous sodium sulfate and ﬁltered for further puriﬁcation.
This high-purity methyl soyate product was characterized for fatty acid methyl ester
content and composition using GC analysis.

One transesteriﬁcation reaction generated about 400 mL of methyl soyate. Thus,
ten batches of soybean oil were transesteriﬁed to methyl soyate. All batches were
collected together in a 4-L amber glass container.

3.3 Ozonolysis of Methyl Soyate

A solution of methyl soyate (100 g), methanol (74 g), and calcium carbonate (10
g) was added to a reaction vessel equipped with a fused ﬁ'itted glass disc. Methanol was
used in excess at a methyl soyate to methanol molar ratio of about 1:4 (theoretical is 1:2)
and the amount of catalyst was chosen to be 1 wt% of methyl soyate. A heterogeneous

catalyst was chosen for easy separation of the products via ﬁltration. The reaction

48

temperature was maintained at ambient conditions by immersing the reaction vessel into
a temperature-controlled water bath. Ozone was produced by passing oxygen through
high voltage electrodes in a Praxair Trailigaz OZOBLOC Model OZC-1001 ozone
generator (Cincinnati, OH). This silent electric-discharge technology is the only
convenient and economical industrial method for ozone synthesis [32]. With tygon
tubing, the exit port of the ozone generator was connected to the inlet port of the bubbling
reactor, which was located underneath the reactor. The gaseous oxygen/ozone mixture
was delivered to the reaction solution through the fused ﬁitted disc at a ﬂow rate of 0.35
ft3/sec, ozone concentration of 6 wt%, and the generator was maintained at a pressure of
12 psi. A 400-mm condenser was attached on top of the bubbling reactor to reﬂux
methanol and other volatile compounds. Via tygon tubing, the exhaust outlet from the
condenser was connected to a 250-mL capacity, round-bottom, ﬂask, which was
immersed in a dewar ﬁlled with dry-ice. The purpose of the dry-ice trap was to collect
any unreacted methanol and volatile compounds produced during the ozonolysis reaction.
A 1000-mL capacity, Erlenmeyer ﬂask containing ~850 mL of a 2% K1 aqueous solution
was placed in series of the dry ice trap. The purpose of this solution was to trap and
rapidly decompose any unreacted ozone. Aﬁer the speciﬁed reaction time, the generator
was shutdown and the reaction products were ﬂushed for 10 minutes with oxygen to
remove excess ozone. The reaction products were separated from the heterogeneous
catalyst via vacuum ﬁltration and stored in a cool environment for further
characterization. The ozonolysis reaction was conducted in a fume-hood environment,
ensuring that ozone was always contained within the reaction system. For kinetics

studies, ozonolysis was conducted in reaction time intervals of 30, 60, 90, 120, 150, and

49

180 minutes, each as a separate and single experiment. To study the effect of catalysis,
ozonolysis was also conducted under non-catalytic conditions. A schematic of the

process ﬂow design is illustrated in Figure 3.2.

 

 

 

O2 Ventilation
Cooling Water _
Electrical
Discharge Condenser
_Cooling
Water
02 " mane;
I I

 

 

 

Dry Ice Trap KI Destruction
o,/o, Delivk U'“‘

Temperature Controlled Water Bath

L

Oxygen Storage

Contained in Fumehood

Figure 3.2 Process Flow Design for the Ozonolysis of Methyl Soyate
3.4 Structural Analysis
3.4.1 Fourier Transform Infra-Red
Fundamental Theory of Operation

Infrared spectroscopy measures the intensity of the absorption of various
frequencies in the infra-red region of the electromagnetic spectrum by a sample. This
analytical technique takes advantage of the fact that almost every carbon-containing
molecule strongly absorbs IR radiation, making IR spectroscopy a useful and powerful
tool for identifying molecular structures within chemical compounds. In fact, the

majority of common organic functional groups absorb infrared radiation between 4000

50

and 400 cm". When a beam of infrared radiation is directed at a sample, some light
passes through (transmitted) and some light is absorbed by the molecules at speciﬁc
frequencies, causing them to vibrate by the bending and stretching of chemical bonds.
The precise frequency of the absorbed radiation, or energy, depends on the functional
group in the molecule. Thus, the absorption intensity as a function of frequency
generates an infrared spectrum of the sample. The infra-red spectrum provides a
“ﬁngerprint” of the molecular chemical bonds present in the sample because no two
unique molecular structures absorb light at the same precise frequency.

The main component of a F ourier-Transforrn Infra-Red spectrometer is the
Michelson interferometer, an Optical device that contains a ﬁxed mirror, a movable
mirror, and a beamsplitter. As shown in Figure 3.3, the incident radiation is split into two
optical beam paths by the beamsplitter. One path travels to a mirror at a ﬁxed distance,
while the other beam travels to a moving mirror whose position varies unifonnly with
time. The two beams recombine back to the beamsplitter by reﬂecting off of these
mirrors, and are then directed to the sample and the detector. An optical path difference
is generated as the moving mirror is moved away from the beamsplitter, causing the two
beams to “interfere” with each other. Thus, an interferograrn is generated, in which the
intensity of the beam striking the detector is measured as a ﬁmction of the movable
mirror position, f(x). This signal is Fourier transformed, a mathematical technique that
“decodes” the interferograrn data and expresses it as a function of frequencies, f(v),

generating an absorption spectrum.

51

 

movable mirror

interference .

   

 

 

 

 

 

E interferograrn, f(x)
E _ j
'8
.3; E: sample and E
detector area _
9 beamsplitter FT calculations
\\/ 3

h

light source

 

 

 

 

mass spectrum, f(v)

Figure 3.3 A Typical Michelson Interferometer

A Perkin-Elmer model Infrared Spectrometer 1000 (Boston, MA), operating at
room temperature, was used to study the degradation of double bonds in ozonated methyl
soyate, with respect to reaction time, and to identify certain functional groups contained
in the ozonated samples. Samples of the volatile fraction collected in the dry-ice were
also examined with respect to reaction time. FTIR spectra (resolution: 2 cm", scan: 64,
frequency range: 4000-500 cm", ﬁ'equency interval: 0.5 cm") were performed aﬁer
spreading a thin ﬁlm of sample between two sodium chloride plates. Sodium chloride is
used because it does not absorb strongly in the infrared region. Because there needs to be
a relative scale for the absorption intensity, a background reference spectrum containing
no sample in the beam was also collected using identical conditions. This technique
results in a spectrum which has all of the instrumental characteristics removed. Thus, all

spectral features that are present in the spectrum are strictly due to the sample.

52

3.4.2 Nuclear Magnetic Resonance Spectroscopy
Fundamental Theory of Operation

Nuclear magnetic resonance spectroscopy (NMR) is based upon the measurement
of absorption of electromagnetic radiation in the frequency range of roughly 4 to 600
MHz. In contrast to ultraviolet, visible, and infrared absorption, nuclei of atoms are
involved in the absorption process. The theoretical basis for NMR is that certain atomic
nuclei have spin and magnetic moment properties and, as a consequence, their energy
levels split when exposed to a magnetic ﬁeld. Therefore, NMR is another excellent tool
for determining functional groups in a pure compound or in complex mixtures.
Analysis

NMR analysis was performed at room temperature using a Varian [nova-3 00
MHz superconducting NMR-Spectrometer (Palo Alto, CA), operating at 300.103 MHz
interfaced with a Sun Microsystems Ultra5 UNIX console. Samples were diluted in
deuterated chloroform (CDCI3).
3.4.3 Gas Chromatography
Fundamental Theory of Operation

Gas-liquid chromatography (GC) is based upon the partition of the sample
components between the mobile phase and a liquid stationary phase immobilized on the
surface of an inert solid. Basic components of a complete gas chromatographic system is
schematically shown in Figure 3.4, which includes the carrier gas supply, ﬂow controller,
injection port, column oven, detector, and a data collection system. A small amount of
liquid sample, 1.0 pL, is injected into the injection port and is volatilized in the hot

injection chamber. The sample is then transported through the column by the ﬂow of an

53

inert, gaseous mobile phase and interacts with the stationary phase. The stationary phase
can selectively adsorb components in a sample mixture based on volatility and/or
polarity. Thus, as a consequence of the difference in mobility due to afﬁnities for the
stationary phase, sample components separate into discrete bands that can be qualitatively
and quantitatively analyzed. The ﬂame ionization detector (FID) generates a measurable
electrical signal, referred to as peaks, that is proportional to the amount of analyte
present. Detector response is plotted as a function of the time required for the analyte to

elute from the column.

 

 

 

 

 

 

Flow lama
controller
I ,
Column oven
Carrier gas

Figure 3.4 Basic Components of a Gas Chromatographic System

The highest precision for quantitative chromatography is obtained by using an
internal standard because the variations introduced by sample injection are avoided. In
this procedure, a carefully measured quantity of an internal standard compound is added
to both the standard solution and the sample, and the ratio of the analyte peak area to the
internal standard peak area serves as the analytical parameter, called the response factor.
Since the internal standard has a known concentration in both the standard solution and
sample mixture, it can be used to correct for sample variations. With a suitable internal

standard, precisions of better than 1% can be achieved [100].

54

For calculating the response factor, the area of a peak due to compound x in the
sample is denoted by AX. In order to relate this area to the area of compound x in the
standard solution, sample variations must ﬁrst be corrected for to arrive at a “corrected

area,” denoted AC X, which can be calculated using equation 3.1.

Ari , CLS.
CI A (3.1)

-5- Standard Solution ['8' Sample

 

[AC/Y :ISample : [AX ample .

where A, C, and LS. denote peak area, concentration, and internal standard, respectively.
Note that the internal standard signal area is proportional to the mass of analyte passing
through the detector. Since mass is equal to the concentration of the internal standard
times the volume, the ratio of NC is equal to the volume times a proportionality constant.
Equation 3.1 results in a cancellation of the proportionality constant, and can be rewritten

33,

(Injected Vol ume ,. S. )

_ , S tan dardSqution
AC X A

’ — X (Injected Volume 1. 5. )Sample (3.2)

to emphasize the importance of the internal standard in correcting for sample volume.
The resulting Ac X is an area that has been corrected to give a volume equivalent to what
would be expected if the internal standard peaks had identical areas in the sample and
standard chromatograms. From the corrected peak areas, the concentration of component

x in the sample mixture can be calculated using equation 3.3,

CX
AX (3.3)

Standard Solution

[CX Lample = [ACX Lample '

55

Equation 3.3 reﬂects the fact that the properly corrected area of compound x in the
sample can be compared with its area in the standard solution, whose concentration is
known.

In this research study, the aforementioned internal standard calibration method
was used to determine the concentration of selected esters in ozonated methyl soyate
samples. Methyl undecanoate (Cu methyl ester) was chosen as the internal standard
because of its predictable retention time and non-interference with the peak areas from all
the components in the sample mixture. Two samples were analyzed for each reaction
time interval, the oil fraction (reaction vessel) and the volatile fraction (dry ice trap). The
oil fraction samples were diluted with methanol to a 1:100 dilution prior to injection. On
the contrary, volatile fraction samples were not diluted because they were already heavily
diluted with unreacted methanol. Thus, two standard solutions were prepared, one
diluted with methanol and one not diluted with methanol. Since the amount of internal

standard that was added to the standard solutions was the same, then equation 3.4,

CLS. _ CLS.

 

A (3.4)

1-5- Oil Fraction Standard 1-5- Volatile Fraction Standard

is validated. The C/A ratio between the oil fraction and volatile fraction standard

solutions were experimentally within 99.5% of each other. Thus, the injected volume of

these standard solutions was assigned 1.0 ,uL as a reference.

56

Analysis

A SGE (Austin, TX) BPX70 capillary column (70% cyanopropyl phenyl , 60-m
length, 0.25-mm i.d., 0.25-pm thickness) was used. The BPX70 is a phase speciﬁcally
designed to aid the selectivity and separation of complex mixtures of fatty acid methyl
esters, including geometric and positional isomers. A Hewlett-Packard instrument (Palo
Alto, CA) Model HP-5890 Series 11 gas chromatograph equipped with and a ﬂame-
ionization detector and a 3396A integrator for data acquisition was used to administer the
analysis. Splitless injection was used at a sample size of 1.0 ,uL. Helium was the carrier
gas at a ﬂow rate of about 10 mL/min. The ﬂow rate of hydrogen was 35 mL/min and
the ﬂow rate of air was about 400 mL/min. The temperature of the injector and detector
was 280°C and 300°C, respectively. For the column temperature programming
conditions, the initial temperature was 50°C and the ﬁnal temperature of 240°C was
reached at a rate of 5°C/min and held isothermally for 22 minutes, giving a total run-time
of 60 minutes.
3.4.4 Gas Chromatography/Mass Spectrometry
Fundamental Theory of Operation

In the gas chromatography/mass spectrometry (GCfMS) analytical technique, gas
chromatography volatilizes and separates the components of a mixture and mass
spectroscopy characterizes each of the compounds individually based on their molecular
weight. In principle, the conventional mass spectrometer is an electronic, high vacuum
instrument used for the analysis of gases or volatilized by means of the dissociation of
molecules by electron impact ionization, chemical ionization, or ﬁeld ionization

bombardment and the subsequent separation of the positive ions according to their mass

57

to charge ratio. Thus, a mass spectrometer creates charged particles (ions) from
molecules and analyzes these ions to provide information about the molecular weight of
the compound and its chemical structure. Since molecules have distinctive fragmentation
pattern (‘ﬁngerprint’), mass spectroscopy is useful for determining chemical and
structural information about compounds.
The gaseous molecules exiting the GC are bombarded by a high-energy, typically
70 eV, beam of electrons in an ionization chamber. As a result of this collision, the
energy impacted is sufficient enough to dislodge one of the molecule’s electrons, as
shown in equation 3.5,
A:B + e' —> (A-B)+ + 2e' (3.5)
(molecule) (electron) (molecular ion) (electron)
The molecular ion produced has the same mass as the molecule from which it is formed.
Electrons with energies of about 70 eV are energetic enough to, not only ionize a
molecule, but also impart a large amount of energy to the resulting molecular ion, causing
it to dissociate into smaller fragments. Dissociation of a cation radical produces a
positively charged fragment and an uncharged fragment, depicted in equation 3.6.
(A-B)+ —> A+ + -B (3.6)
(molecular ion) (fragment cation) (fragment ion)
The positively charged fragments are accelerated by an electric ﬁeld and pass through
slits to form a narrow, well-focused beam. This beam of ions then passes through an
applied magnetic ﬁeld. Because an accelerating ion produces its own magnetic ﬁeld, an
interaction with the applied magnetic ﬁeld occurs, causing the trajectory of the path of

ions to change. The amount of path deﬂection for each ion depends on its mass/charge

58

ratio (m/z). Thus, the original beam splits into several beams- ions of small m/z are
deﬂected more than those of larger m/z, causing the ions to separate. In electron impact
ionization, singly charged particles are produced, so the charge, 2, is one. Therefore, an
ion’s path will depend on its mass. Only charged particle will be accelerated, deﬂected
and detected by the mass spectrometer. The uncharged particles are removed by a
vacuum pump. The detector converts the beam of ions into an electrical signal that can
be processed and records the abundance of each m/z. Scanning all m/z values give the
distribution of positive ions characteristic of a particular molecule, called a mass
spectrum. Therefore, the mass specn'um is essentially a ﬁngerprint for the molecule,
which is used to identify the compound or components of a mixture. A schematic

representation of a mass spectrometer is shown in Figure 3.5.

 

 

 

 

I
bump: EVA-ﬂ ‘M

 

Figure 3.5 A Typical Mass Spectrometer

59

Analysis

GC/MS analysis was performed using electronic impact (EI) ionization mode on a
J EOL AX-505H double -focusing mass spectrometer (J EOL, USA, Peabody, MA)
interfaced with a Hewlett-Packard 58901 gas chromatograph. A BPX70 capillary
column (70% cyanopropyl phenyl , 60-m length, 0.25-mm i.d., 0.25-pm thickness) from
SGE (Austin, TX) was used for the separation of esters. A scanning rate of 5°C/min
from a starting temperature of 50°C to a ﬁnal temperature of 240°C was employed,
holding the ﬁnal temperature isothermally for 22 minutes. An ionization voltage of 70
eV over the mass scanning range of 45-750 atomic mass units was used to fragment the
components. The carrier gas was helium and splitless injection at a volume of 1.0 ,uL
was used. Other operating conditions were injector temperature of 250°C, interface
temperature of 240°C, and ion source temperature of 200°C. A NIST/EPA/NIH Mass
Spectral Library, Version 2.0, was used for compound identiﬁcation. Also, a ShraderTSS
Pro, Version3.0, operating system (Shrader Analytical and Consulting Labs, Detroit, MI
& J eol Ltd, Peabody, MA) was used for data collection and analysis.
3.5 Thermal Analysis
3.5.1 Thermogravimetrical Analysis
Fundamental Theory of Operation

Thermogravimetry (TGA) is a technique that monitors the mass of the sample as a
function of time or temperature in a controlled atmosphere. TGA can also measure the
rate of change (derivative) in the weight of a material as a function of temperature or
time. This analytical method is most frequently used for thermal stability studies

resulting in changes of mass, including oxidative stability and thermal degradation.

60

A sample is placed into a tared sample pan, which is attached to a sensitive
thennobalance assembly. The sample is suspended directly from the balance beam in
order to hang down into a controlled-temperature furnace. In the TGA 2950 design (TA
Instruments, New Castle, DE ) horizontal purge gas ﬂow is used to ensure good
interaction between the sample and purge gas, as well as rapid removal of decomposition
products so that undesired recombination effects and interactions of the product gases
with the sample suspension system are minimized, reducing weigh loss peak broadening.
The sample may be heated or cooled at a selected heating rate (dynamic mode), or it may
be maintained under isothermal conditions (static mode). The balance assembly
measures the initial sample weight at room temperature and then continuously monitors
changes in sample weight as heat is applied to the sample. Figure 3.6 shows a schematic

for the TGA 2950 therrnogravirnetric analyzer.

F

Purge gas

 

 

Thermobalance

Furnace
housing

 

 

 

 

 

 

 

 

Figure 3.6 TGA 2950 Thermogravimetrical Analyzer

61

Analysis

TGA volatility studies were carried out with a TA Instruments Model TGA 2950
therrnobalance (New Castle, DE). The instrument was operated in the dynamic mode
with a heating rate of 10°C/min, where 40°C and 350°C were the initial and ﬁnal
temperatures, respectively. On average, 5 mg was the initial mass of each sample
analyzed. A reactive atmosphere (air purge gas) surrounding the sample was used to
study the effect of air oxidation on volatility and to simulate the environmental conditions
of a diesel engine combustion chamber. For oxidative stability studies, the instrument
was operated in the static mode at 350°C.

3.5.2 Differential Scanning Calorimetry
Fundamental Theory of Operation

Differential scanning calorimetry (DSC) is a technique used to measure the heat
ﬂow associated with thermal transitions in materials as a function of time and
temperature, while the temperature of the sample is programmed in an inert or reactive
atmosphere. This technique provides qualitative and quantitative information about
physical and chemical changes that involve endothermic or exothermic processes. DSC
is the most widely used method for thermal analysis.

Figure 3.7 shows the cell compartment of a DSC instrument. A sample pan and
an equivalent empty reference pan are equally positioned on identical platforms. These
platforms are connected by a constantan thermoelectric disk and surrounded by a
controlled temperature ﬁIrnace. Purge gas is administered to both the reference and
sample chamber through an oriﬁce in the heating block wall midway between the

platforms. The gas is preheated by circulation through the block before entering the

62

sample chamber. This circulation process .provides a uniform, stable thermal environment
which assures excellent baseline ﬂatness and exceptional sensitivity. As the furnace
temperature is heated, or cooled, at a constant scanning rate, heat is symmetrically
transferred to the sample and reference through the thermoelectric disk. When the cell
arrangement is identical, the same amount heat ﬂows into both the sample and reference.
Thus, the differential temperature is zero. However, when this steady-state equilibrium is
disturbed by a physical or chemical change of the sample, a temperature difference
between the sample and the reference is produced. As a result of this transition, a
differential heat ﬂow between the sample and reference is established and measured by
thermocouples welded beneath each platform. This measured differential heat ﬂow is
converted to differential power as the signal output and recorded as a peak on the
thermogram. The area under the peak is directly proportional to the enthalpic change of

the sample.

Reference
Pan

  
     

  

Thermoelectric
Disk

  

2 \
’
I/

‘

Thermocouple
Junction

4

Heating Block

 

 

 

 

\

Figure 3.7 Cell Compartment of a Differential Scanning Calorimeter

63

Analysis

DSC analysis was carried out with a TA Instruments (New Castle, DE) model
DSC 01000, equipped with a 50-position auto-sampler, PC-based controller, and a
refrigerated cooling system (RCS) for sub-ambient temperature scans. The TA
Instruments DSC Q series are speciﬁcally designed to take into consideration extraneous
heat ﬂow effects using the advanced T25R07” technology (TA Instruments, New Castle,
DE), accounting for the cell resistances and capacitances, as well as pan effects [101].
The DSC chamber was continuously purged with low-pressure nitrogen gas (99.9999%
purity) at a ﬂow rate of 50 mL/min, to create a reproducible and dry atmosphere. On
average, 10.0 mg samples were weighted to the nearest 0.1 mg with a microbalance and
sealed in alumintun pans. An empty, sealed aluminum pan was used as a reference. For
cooling scans, samples were ﬁrst held isothermally at 40°C for 10 min to establish
thermal equilibrium. Previous studies have shown that calorimetric properties vary
signiﬁcantly with temperature scanning rate [27, 102]. It was concluded that, in order to
obtain thermal event temperatures close to the thermodynamic value and high accuracy
measurements, slow scanning rates should be used. A scanning rate of 5°C/min is a
convenient and reliable rate to use because it gives a good combination of resolution and
ﬂat baselines [27]. Therefore, aﬁer equilibration, the samples were then cooled to —90°C
at a cooling rate of 5°C/min and held isothermally for 10 min, then heated back to 40°C
at the same rate. Each sample was scanned three consecutive times to eliminate thermal
history. The third scan of every sample was taken as the experimental data. Heat ﬂow

vs. temperature thermograms were analyzed to determine the crystallization properties of

64

the samples. The DSC instrument was calibrated with high purity metal indium (melting
point: 156.51°C, AHfusion: 28.71 J/g)
3.5.3 Low-Temperature Flow Properties
Fundamental Theory of Operation: CP, PP, and CFPP

The petroleum industry routinely uses cloud and pour points to characterize low-
temperature properties of diesel fuels. The cloud point measures the temperature at
which wax ﬁrst becomes visible when the fuel is cooled, and the method is published by
the ASTM with the designation D 2500 [103]. In the test, a small sample of the fuel is
placed in a glass jar, cooled at a speciﬁed rate and examined at intervals of 1°C. A
thermometer is immersed in the fuel to measure the temperature at the bottom of the jar,
where the ﬁrst waxes appear. It is a subjective test, depending on the operator’s
judgment that wax particles are visible. The pour point test is used to measure the
temperature at which the amount of wax out of solution is sufﬁcient to gel the fuel. It is
carried out in a similar fashion and under the same controlled cooling conditions as the
cloud point test, except that the thermometer is located with its bulb just below the
surface of the fuel, and checks on the conditions of the fuel are made at intervals of 3°C.
Checks are made by brieﬂy removing the test jar from the cooling bath and tilting it to
see whether the fuel ﬂows. This procedure is continued until the fuel fails to move when
the jar is held horizontally for 5 seconds. The pour point test method is published as
ASTM D 97 [104]. The experimental apparatus for both the cloud and pour point tests

are identical and is illustrated in Figure 3.8.

65

 

 

   

 

Cooling Bath —
Disk ""

 

 

 

Figure 3.8 General Apparatus for Cloud and Pour Point Measurement

The cold ﬁlter plugging point represents the highest temperature at which a given
volume of fuel fails to pass through a standardized ﬁltration device in a speciﬁed time
when cooled. In this test, a sample of the fuel is cooled under speciﬁed conditions and, at
1°C intervals, is drawn into a pipette under a controlled vacuum through a standardized
wire mesh ﬁlter. Testing is continued until the amount of wax crystals that have
separated out of solution is sufﬁcient to stop or slow down the ﬂow so that time taken to
ﬁll the pipette exceeds 60 seconds or the fuel fails to return completely to the test jar
before the fuel has cooled by a further 1°C. The indicated temperature at which the last
ﬁltration was commenced is recorded as the cold ﬁlter plugging point. The most
common standard method used to measure the cold ﬁlter plugging point is ASTM D 6371

[105] and the general apparatus is depicted in Figure 3.9.

66

 

 

 

 

 

 

 

 

 

 

 

 

Figure 3.9 General Apparatus for Cold Filter Plugging Point Measurement
Analysis

The low-temperature ﬂow properties (CP, PP, CFPP) on selected ozonated methyl
soyate samples were conducted at Savant, Inc. (Midland, MI), an independent laboratory
and research center that specializes in ASTM and custom tests on engine oils,
transmission ﬂuids, and other lubricants. The test methods used to measure cloud point,
pour point, and cold ﬁlter plugging point were ASTM D 2500, D 97, and D 6371,
respectively.
3.5.4 Viscosity Measurements
Fundamental Theory of Operation

Viscometry deals with the measurement of the ﬂow behavior of liquids. Common
instruments, capable of measuring fundamental rheological properties can be categorized
as rotational type and tube type [106]. There are three types of shear-induced liquid ﬂow
models for rotational type viscometers, including ﬂow between a cone and plate, ﬂow
between two parallel plates, and circular ﬂow in the annular gap between two concentric
cylinders. Of the three aforementioned models, the concentric cylinder rotational

viscometer is a very common instrument for viscosity determination [106].

67

The most common design for rotational viscometers is the Searle system,
illustrated in Figure 3.10. In this system, the inner cylinder, often referred to as the
spindle, rotates at a speciﬁed, constant speed (n), while the outer cylinder is stationary.
The rotating inner cylindrical spindle forces the liquid in the annular gap to ﬂow, causing
the sample to exert a resistance, or shear stress, to this rotational movement due to its
viscosity. The spindle is operated by a synchronous motor through a calibrated torsion
spring. The torque of the ﬂuid against the spindle causes the spring to deﬂect. Thus, the
viscometer measures the torque (Md) required to maintain a constant angular velocity of
the cylindrical spindle while immersed in the sample. This measured torque is
proportional to the viscosity of the sample and is dependent upon a spindle’s rotational
speed and geometry. The major advantages of a rotational coaxial cylinder viscometer,
also called a Brookﬁeld viscometer, are that continuous measurements can be made at a
given shear rate, the dependency of viscosity on time can be readily determined, making

it suitable for measuring the viscosity of Newtonian and Non-Newtonian ﬂuids.

 

Motor

 

 

 

torque sensor, Md

" speed, n

——-D
MM

 

 

 

----- p---

 

 

 

--
-p- ‘

2°

5.

3°

1

Figure 3.10 Searle-Type Rotational Viscometer

68

Shear rates and shear stresses are mathematically deﬁned for rotational
viscometers. By deﬁnition, viscosity describes the relationship between shear stress (I)

and shear rate (7 ):

n = . (3.7)

r
7
Starting with the measured values for torque (Md) and rotational velocity (n), the

geometric characteristics of a particular spindle sensor system are accounted and are

inherent in equation 3.7 by the spindle geometrical factors f and M. Thus, it can now be

supplemented as follows:

 

 

 

- Md
77 = fM .n (3.8)
For cylindrical systems:

2

f = 2:22} and M = % Kirk} (3'9)
where:
R,- = spindle radius [m]
Ra = cup radius [m]
n = speed of spindle [min"']

The following assumptions are made in developing the mathematical relationships: ﬂow
is Iarninar and steady, end effects are negligible, test ﬂuid is incompressible, properties
are not a function of pressure, temperature is constant (i.e., no increase in temperature
due to viscous heating), no slip at the walls of the instrument, and radial and axial

velocity components are zero [106].

69

Analysis

A HAAKE VT550 viscometer (Pararnus, NJ) was used to measure the viscosity
of selected oil samples at 10°C, 25°C, and 40°C. Spindle type “MV” for the HAAKE
VT550 viscometer is primarily used for viscosity measurements of medium-viscosity
liquids, such as oils, paints, and emulsions, working in the medium shear rate range.
Therefore, this spindle type was used in all viscosity measurements. Table 3.1 lists the
spindle’s geometric parameters.

Table 3.1 Spindle Geometric Parameters

 

 

 

Inner Cylinder (Rotor) Outer Cylinder (Clm) Radii Ratio RJR, 1.05
Radius, R, (m) 20.04 Radius, Ra (mm) 21.0 Gap Width (mm) 0.96
Height, L (m) 60.0 Sample Volume (cm3) 34.0

 

 

 

7O

Chapter 4

Results and Discussion Part 1:
Structural Analysis & Reaction Kinetics

4.1 FT IR Analysis

Direct structural evidence to the nature of catalytic ozonolysis can be observed
from the FTIR spectra as a ﬁrnction of reaction time, which shows the absorption of
common functional groups found in the ozonated oil at various frequencies. Figure 4.1
shows the FTIR spectra for the catalytic ozonolysis of low-sat methyl soyate, with a
frequency range of 400-4000 cm". In order to see the absorption intensities more clearly,
the spectrum was divided into two separate regions, A (2400-3 800 cm") and B

(400-2000 cm"), plotted in Figures 4.2 and 4.3, respectively.

 

Region A Region B

 

 

 

 

 

 

Normalized Absorbance

 

 

 

 

4000 3400 2800 2200 1600 1000 400

Frequency (cm'l)

Figure 4.1 FT IR Spectra for the Catalytic Ozonolysis of Low- Sat Methyl Soyate

71

In region A, a small broad peak is observed at around 3460 cm], characteristic of
a hydroxyl functional group, OH, and its intensity increases with reaction time. This
hydroxyl peak is characteristic in alcohols, hydroperoxides, and carboxylic acids. The
typical frequencies of an OH functional group attached to an oxygen atom, like in
hydroperoxides, is signiﬁcantly different from those of carboxylic acids and alcohols.
Due to electronegativity differences, the 0H stretching mode in hydroperoxides fall at a
distinctly higher frequency than in alcohols, which was assigned a value of 3450 cm'1
[107]. According to the GC/MS data, discussed in more detail later, no carboxylic acids
are detected in the ozonated oil fraction. Moreover, methanol is being consumed as the
reaction progresses, which should result in a decrease, rather than an increase, in the
absorption intensity of OH. Thus, it may be deduced that the OH functionality is
attributed to hydroperoxides rather than methanol or carboxylic acids. This conclusion is
also consistent with the mechanism proposed by Marshall et al. for the oxidative cleavage
of alkenes in the presence of methanol. In the mechanism, water is a by-product in the
conversion of both the hemiacetal and hydroperoxide intermediates to methyl esters
(refer to Figure 1.8). As mentioned in Chapter 1, the secondary ozonide from the
combination of the carbonyl compound and carbonyl oxide intermediate, can react with
water to produce carbonyl compounds and hydrogen peroxides (refer to Figure 1.6).
Likewise, the carbonyl oxide intermediate can react with protic solvents, like water and

methanol, to produce hydroperoxides (refer to Figure 1.6).

72

‘1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Region A CH3, CH2

- 6 C=C I / (CH
°’ OH A °
g _ 5 180 mins
g A 150 mins
'2 .. 4 A 120 mins
1:
.38). P 3 A 90 mins
g - 2 A 60 mins
2 _ I A 30mins

_0 A 0 mins

 

3800 3600 3400 3200 3000 2800 2600 2400

Frequency (cm")

Figure 4.2 FT IR Spectra for the Catalytic Ozonolysis of Low- Sat Methyl Soyate:
Region A

The double bonds, C=C, in the fatty esters were readily attacked and cleaved as
expected, which is indicated by the disappearance of the absorbance stretching peak at
around 3000 cm", with respect to reaction time. Furthermore, the increase in peak height
of the methyl group, CH3, at 2940 cm", suggests the formation of additional methyl
groups in the ozonated oil. The additional methyl groups arise from the formation of
dimethyl esters, where CH3 is located at both terminal ends of the molecule, and methyl
esters alike.

Figure 4.3 shows region B of the FTIR spectra for the catalytic ozonolysis of low-
sat methyl soyate. The broadening of the carbonyl peak, C=O, at 1740 cm'1 as a function
of time suggests that additional carbonyl groups are formed. The C=0 functional group
is characteristic in carboxylic acids, ketones, aldehydes, and esters. However, based on

GC/MS experimental data, the C=O functionality in the ozonated ﬁre] is most likely due

73

to the presence of esters and aldehydes. The formation of aldehydes may be a result of
the secondary ozone, 1,2,4-trioxolane, reacting with water. Moreover, the C — CH3
absorption peak at 1360 cm'1 becomes more intense as the reaction time increases,

indicating a high concentration of terminal alkyl hydrocarbon chains.

 

’1
I

C=O C— CH3 C"-()ester Region B

F 6 CH2 1 CH A {C-Oozonide
I \ AM“ V \—\ (CH2)4 180 mins
I \ M MVV \_..._ 150 mins

'4 I\ M _. N . 120mins
"'3 I\ M _ MA 90mins
"2 W~ 60mins
' #A—_——_
__~_—
II :3 $ 0mins
I I+T FA

2000 1800 1600 1400 1200 1000 800 600 400

Frequency (cm'l)

 

 

Normalized Absorbance

 

 

 

 

Figure 4.3 FTIR Spectra for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:
Region B

A distinct absorption peak at 1100 cm‘1 is evident only after the start of
ozonolysis and becomes more intense as the reaction time increases. The characteristic
bands of the ﬁve-member ozonide ring usually differ from the spectra of other peroxy
compounds and lie in the 950-1150 cm'l frequency range [34]. Shown from the data
presented in Table 4.1, the infra-red spectra of monomeric and polymeric ozonides are
essential identical. Criegee et al. [108] studied the infra-red absorption of 18 various

types of ozonides and noted that, in the majority of them, a new strong absorption band

74

appeared after ozonolysis in the 1064-1042 cm-1 frequency range. Briner and Dallwigk
[109-111] conﬁrmed this ﬁnding, and Garvin and Schubert [112] also found ozonide
absorptions in this region. Thus, the 1100 cm'1 absorption peak present in ozonated
methyl soyate is characteristic of an ozonide moiety. Since the infra-red spectra of
monomeric and polymeric ozonides are essentially identical, the ozonides formed in the
ozonation of methyl soyate may be a mixture of these products. In the proposed
mechanism for the conversion of alkene to esters, the extent to which the primary
fragments recombine to form the secondary ozonide depends on steric effects [3 5]. For
example, no secondary ozonide is observed with the ozonolysis of mono-substituted
oleﬁns, whereas the ozonolysis of di- and tri-substituted systems give rise to signiﬁcant
quantities of the secondary ozonide [3 5]. These results are compared in Table 4.2 and
Figure 4.4. Therefore, secondary ozonides present in ozonated methyl soyate may have
been formed as a result of steric effects inherent in the structure of methyl soyate, which
is a mixture of long-chain saturated and unsaturated hydrocarbons.

Table 4.1 Characteristic Absorption Frequencies for Several Ozonides

 

 

 

 

 

 

 

 

Compound Structure Absorption
(C-O ring bond)
cm'l
O—O
Monomeric ozonide / \ a
of l-hexene CH3(CH2)3CH 0 [CH2 1100; 1040; 985
Polymeric ozonide O — CH-OO-CH2
of l-hexene ' 1100; 1040; 985“
(CH2)3CH3 x
. . 0 —O b
Monomerrc ozonide / \ 1109, 1110, 1109
of methyl oelate CH3(CH2)7 C Ii / C H(CHz)7COOCH3
O

 

“Ref. [113]; [Ref [114]

75

Table 4.2 Direct Conversion of Olefms to Esters: Nomenclature and Yields

 

 

 

 

Reaction A
R; R2 A1, yield, %
CH3(CH2)5 (hexyl) CH3 (methyl) 63
Reaction B
R. R2 R3 Bl, yield, % B2, yield, %
CH3 (methyl) H H 56 19
CH3(CH2)3 (butyl) H H 57 29
0R2 03, NaOH 0R2 O A
R M MeOH, CH2C12 R &
I _78°C I
OMe
A1
OR] R1 o-o
\ R2 03, NaOH ) B
MeOH, CH2C12 0
R3 -78°C BZ

 

 

 

Figure 4.4 Direct Conversion of Oleﬁns to Esters
Adopted from Ref. [3 5]

The FTIR spectra for the volatile fraction of ozonated low-sat methyl soyate
under catalytic conditions is depicted in Figure 4.5. Based on GC/MS data, the 0H
absorption peak, 3340 cm’l, is mainly due to the presence of excess or unreacted
methanol and trace amounts of carboxylic acids. The C-O absorption peak characteristic
of an ozonide, 1026 cm", is more prevalent in the volatile fraction than in the oil fraction,
conﬁrming that ozonides are being condensed and collected in the dry-ice trap before
unreacted ozone is decomposed in the K1 destruction tmit. The C-O peak, 1100 cm", due

to the presence of esters, is also distinct in the volatile fraction spectra.

76

 

 

 

 

 

CH3, CH2 esterC-gozonide
Q, - 5 OH \ /CH CH
g __/\./\k 180 mins A 2
3 150 mins
< - 3
'8 A 120 mins IVA‘A
.5
g -2___/\/\\ 90 mins A'ML‘d
e
Z _. .L_/\/\'\ 60 minsWL

 

 

 

 

 

MO mins

4000 3400 2800 2200 1600 1000 400
Wavenumber (cm'l)

Figure 4.5 FTIR Spectra for the Catalytic Ozonolysis of Low-Sat Methyl Soyate:
Volatile Fraction

The FTIR spectra for the non-catalytic ozonolysis of low-sat methyl soyate, non-
catalytic and catalytic ozonolysis of regular methyl soyate, were all analogous to that of
the catalytic ozonolysis of methyl soyate. The difference in their spectra is the absorption
intensities. Table 4.3 lists the theoretical and experimental frequencies of the functional

groups present in both the oil and volatile fractions of ozonated methyl soyate.

Table 4.3 Theoretical and Experimental Absorption Frequency Ranges for
Common Functional Groups Present in Ozonated Methyl Soyate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Stretching Mode Bending Mode
Theoretical Experimental Theoretical Experimental
Functional Frequency” Frequency Frequency” Frequency
Group cm' cm' cm' cm'
Alkanes
CH3 2850-2950 2940 -- --
C - CH3 -- -- 1370-1380 1365
CH2 2900-2940 2925 1445-1485 1430-1460
1400-1440*
(CH2)4 -- -- 750-720 720
CH 2850-2970 2850 1240-1470 --
Akenes
C = C 3010-3040 3000 -- --
_ﬂ;droxvl
OHalcohol 3280-3450 3340* 1260-1350 --
OHcarboxlyic acid 3500-3 600 3340* -- --
Othdroperoxidc 3450’3650 3450 " "
Carbonyl
C : Oester 1717-1750 1740 -- --
CZOaIdChYde 1660-1740 1740 -- --
C _ 0 1025-1300 1170-1190 -- --
1 100*
Ozonides 1042-1064 1100 -- __
1026*

 

“Source: Ref. [115], *Denotes the frequencies for the volatile fraction

78

 

4.2 NMR Analysis

Selected ozonated methyl soyate samples of both low-sat and regular were
analyzed by lH NMR to conﬁrm the existence of ozonides and hydroperoxides. In
general, the proton in the 1,2,4-trioxolane ring resonated at about 65.15 ppm. The
aldehydic proton is also detected at both 6 9.75 and 6 9.63 ppm, while6 5.55 ppm is the
oleﬁnic signal from hydroperoxides. These speciﬁc resonances were absent in non-
ozonated methyl soyate. The 1H NMR spectra for non-ozonated and ozonated low-sat
methyl soyate are depicted in Figures 4.6 and 4.7, respectively. The experimental
ﬁndings were consistent with those found in the literature, based on the ozonation of
various pure esters and vegetable oil. The 1H NMR spectrum of methyl linoleate
ozonation in ethanol showed multiplets between 6 5.10 and 65.3, attributed to the
Criegee ozonide signal, and a triplet at 69.75 from the aldehydic proton [116].
Ozonolysis of sunﬂower oil in the absence and presence of water was monitored by lH
NMR [117]. The NMR analysis showed that products in both cases included aldehydes,
69.75, and ozonides with 1,2,4-trioxolane ring, 6 5.17. Diaz et al. [118] conducted
spectroscopic characterization experiments for the ozonation of sunﬂower oil. Ozonation
products of sunﬂower oil were identiﬁed by 1H, 13'C, and two-dimensional 1H NMR. The
virgin sunﬂower oil and ozonated sunﬂower oil showed very similar 1H NMR spectra;
except for the resonances at 6 9.74 and 69.63 ppm, both corresponding to aldehydic
protons, 6 5.60 ppm, the oleﬁnic signal from hydroperoxides, and 65.15 ppm, proton

from ozonides.

79

solvent
alkene

L

[IIIt]Irrr'rrrrlﬁﬁrrllrrrjrrlilppm
10 9 8 7 6 5

Figure 4.6 1H NMR Spectra for Non-Ozonated Low-Sat Methyl Soyate

 

solvent

\ alkene ozo/nide

aldehyde
hydroperoxide

 

 

 

 

 

 

10.0 9.5 9.0 8.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5

Figure 4.7 1H NMR Spectra for the Catalytic Ozonated Low-Sat Methyl Soyate
4.3 GC Analysis
T ransesteriﬁcation

Transesteriﬁcation reaction experiments were carried out for both regular and
low-sat RB soybean oil. The fatty acid composition, shown in Table 4.4, for both
transesteriﬁed oils (methyl soyate) was determined by GC, using the internal standard
quantiﬁcation method described in Chapter 3. The fatty acid composition of regular

methyl soyate was comparable to other published data [98, 119]. Low-sat methyl soyate

80

contained about half of the amount of saturation contained in regular methyl soyate.

Figures 4.8 and 4.9 show the chromatograrns for low-sat and regular methyl soyate,

respectively. The peak that eluted at a retention time of about 29 minutes is methyl

undecanoate, the chosen internal standard.

Table 4.4 Fatty Acid Composition of Transesteriﬁed, RB Soybean Oils

 

 

 

 

 

 

Low-Sat Soybean Regular Soybean
Component Retention Time Weight Retention Time Weight
mins (%) mins %
Methyl Palmitate 39.586 3.93 39.638 10.25
Methyl Stearate 43.665 3.75 43.570 4.89
Methyl Oleate 44.302 24.76 44.207 24.36
Methyl Linoleate 45.529 58.86 45.420 51.89
Methyl Linolenate 46.646 8.70 46.572 8.61
ox
N
'0.
If)
V
N
o
"l
a 3
q so
a j g.
V
o
00
'0.
C75
('3
II)
o
‘9
M
V
J U LI L

 

 

 

 

 

 

 

 

 

Figure 4.8 Chromatogram of Transesterified Low-Sat Soybean Oil

81

j 45.420

 

 

 

 

 

 

[x
O
N.
l‘
l‘ w 3
q m
o 0.
N
33 a
'0.
\O
v
C
(x
'0.
M
v

 

 

 

 

 

Figure 4.9 Chromatogram of Transesterified Regular Soybean Oil
Ozonolysis & Reaction Kinetics

The reactor system for the ozonolysis of methyl soyate was modeled as a semi-
batch reactor. The semi-batch reactor is typically used for two-phase reactions in which a
gas is usually bubbled continuously through a liquid [120]. For a constant-volume batch
system, the mass balance for component i is

_iC_:
’ dt

(4.1)

Thus, the rate of reaction of any component is given by the rate of change of its
concentration. For a constant-volume reactor, it is assumed that the reactor is perfectly
mixed so that the concentration of the reacting species is spatially uniform. In this study,

the concentration of selected reaction components was quantiﬁed using the internal

82

standard method from the GC data. Both the differential and integral methods were used
to determine the reaction order, a, and the reaction rate, k, for each speciﬁed reactant
component of the methyl soyate mixture.

Integrating equation 4.1 with C, = C ,0 at t = 0, and setting r2 equal to the reaction
constant, k,, for a zero-order reaction,

C, = C1, — k,t (4.2)

Thus, a plot of the concentration of component i as a function of time is linear with slope
k. Methyl palmitate, stearate, and oleate all ﬁt a zero-order equation for the ozonolysis of
regular and low-sat methyl soyate, under both catalytic and non-catalytic conditions
alike. Figure 4.10 shows the kinetic data for these three constituents in the catalytic
ozonolysis of low-sat methyl soyate. Each data point represents a single ozonolysis
reaction. The reaction rate constants for methyl palmitate, stearate, and oleate for the
ozonolysis of low-sat and regular methyl soyate, are compared in Tables 4.5 and 4.6,
respectively. In general, the rate of reaction was slightly faster in the presence of the
alkaline catalyst, as expected. For methyl palmitate, the reaction rate for ozonated
regular methyl soyate was nearly twice that for ozonated low-sat methyl soyate. Regular
and low-sat methyl soyate are comprised of about 85 wt% and 92% unsaturates,
respectively. So, the starting concentration of double bonds is less for regular methyl
soyate, which may result in an increase in the reactivity of methyl palmitate. Moreover,
the reaction rate constants for low-sat methyl stearate and oleate are slightly higher than
that of regular methyl stearate and oleate. This observation may be due to less steric
hindrance, or steric effect arising from the crowding of molecules, in low-sat methyl

soyate because of the reduced amount of saturated molecules. Therefore, these

83

experimental ﬁndings suggest that the kinetics of methyl soyate is inﬂuenced by both the

amount of double bonds and steric effects inherent in its molecular structure.

 

 

 

 

30 l 200
no 0
>1: 25 = . F 160 8
A ' i : 8
j 20 - ‘ ° 0 3
ED ‘ - ' 120 g.
E o
v 15 - ' a
r: A A
.2 B
a . ' 80 2%
15:: 10 - t"
8 0 Methyl Pahnitate ‘ V
s: . 40 >4
8 5 I Methyl Stearate . '5’
A Methyl Oleate“ w

0 I T I O
0 50 100 150 200

Reaction Time (mins)

Figure 4.10 Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate: Methyl
Palmitate, Methyl Stearate, Methyl Oleate Constituents
*Data is on the secondary y-axis

Table 4.5 Reaction Rate Constants for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Palmitate, Stearate, Oleate Constituents

 

 

 

 

 

 

 

 

 

 

 

Catal 1c
Component Estimate of k Standard 95% Conﬁdence R2
Qng 41L) x 103-min" Error Level
Methyl Palmitate -0.0353 $0.00295 (-0.0428, -0.0277) 0.966
Methyl Stearate -0.0476 $0.00556 (-0.0619, -0.0333) 0.936
Methyl Oleate -0.710 $0.0429 (-0.820, -0.560) 0.982
Nonfgtilvtic
Component Estimate of k Standard 95% Conﬁdence R2
(mg lpL) x 103-min'l Error Level
Methyl Palmitate -0.0257 $0.00789 (-0.0460, -0.00539) 0.679
Methyl Stearate -0.0426 $0.00241 (-0.0488, -0.0364) 0.984
Methyl Oleate -0.704 $0.0455 (-0.821, -0.587) 0.980

 

 

 

 

84

Table 4.6 Reaction Rate Constants for the Ozonolysis of Regular Methyl Soyate:
Methyl Palmitate, Stearate, Oleate Constituents

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

satanic
Component Estimate of k Standard 95% Conﬁdence Rf
(mg ALL) x 103-min'l Error Level
Methyl Palmitate 00754 $00138 (-0.111, -0.0400) 0.857
Methyl Stearate 00268 $00101 (-0.0527, -0.000833) 0.585
Methyl Oleate -0.650 $00549 (0791, -0.509) 0.966
Non_-C_?Lalvtic
Component Estimate of k Standard 95% Conﬁdence R2
(mg lpL) x 103-min'I Error Level
Methyl Palmitate 00606 $00133 (-0.0948, -0.0265) 0.806
Methyl Stearate 00241 $000932 (-0.0481, -0.000142) 0.572
Methyl Oleate -0.636 $00479 (0759, -0.513) 0.972

 

 

 

 

Shown in Figure 4.11, the concentration-time data for the polyunsaturated methyl
esters, linolenate and linolenate, ﬁt very well to 2"d-order polynomials. This observation
holds true for ozonated low-sat and regular methyl soyate under both catalytic and non-
catalytic conditions. Therefore, the differential method for rate analysis was used to
analyze the kinetics of these two constituents. In the this method of rate data analysis, it

is assumed that the rate law is of the form
— r, = kCla (43)
where a is the reaction order [120]. Combining equation 4.1 and 4.3 and taking the

natural logarithm,

ln(— 61:1ng = In k, + a In C, (4.4)

Thus, the slope of plot ln(-dC/dt) versus ﬂn/C.) is the reaction order, a, and the y-
intercept is the natural logarithm of the rate constant, k, depicted in Figure 4.12. The
kinetic data for the ozonolysis of low-sat and regular methyl soyate containing the

polyunsaturated constituents are compared in Tables 4.7-4.10. For the methyl linoleate

85

constituent, the rate of reaction was slightly faster under catalytic conditions. As
previously mentioned, there is less steric hindrance in the low-sat mixture because the
bulky long-chain saturated hydrocarbons are reduced to half the amount compared to that
of regular methyl soyate. Moreover, the starting amount of polyunsaturates is greater for
low-sat methyl soyate, increasing the reactivity of these compounds due to the presence
of double bonds. Thus, the rate of reaction is faster when both linoleate and linolenate
are comprised in the low-sat mixture. It appears that, for methyl linolenate, the presence
of the catalyst has no effect on the reaction rate. Moreover, the degradation of methyl
linolenate was approximately three times faster than that of methyl linoleate. This
observation suggests that the rate of ozonolysis is heavily dependent on the number of
double bonds in the mixture, as predicted. For example, in lipid oxidation, the relative
autoxidation rate of methyl linoleate to methyl linolenate was found to be about 121.5

[12].

86

\l
O

 

500

0 Methyl Linolenate----
I Methyl Linoleate“

05
O

r 400

£11
O
I
b)
O
O

£01 x (111 /8ur) uouenuaouog

r
N
O
O

20"

f
p—i
O
O

Concentration (mg/uL) X 103

10-

 

 

 

 

0 50 100 1 50 200
Reaction Time (mins)

Figure 4.11 Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate: Methyl
Linoleate, Linolenate Constituents
*Data is on the secondary y-axis

 

 

2
I Methyl Linoleate
0 Methyl Linolenate
1 ..
“:5 0 l r- I
‘13 ii 2 6 t
E -1 "l
-2 I

 

 

-3

 

In (C)

Figure 4.12 Linear Relationship of the Kinetics for the Catalytic Ozonolysis of Low-
Sat Methyl Soyate: Methyl Linoleate, Linolenate Constituents

87

Table 4.7 Reaction Rate Constant for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Linoleate, Linolenate Constituents

 

 

Catalgic Ozonolysis

 

 

 

 

 

 

 

 

 

 

 

Component Estimate of In k Standard 95% Conﬁdence R2
[(mg/uL) x 103]"“-min'l Error Level
Methyl Linoleate -2.22 $00804 (-2.43, -2.01) 0.996
Methyl Linolenate -3.30 $0.214 (-3.89, -2.70) 0.963
Non-Catalgic Ozonolysis
Component Estimate of In k Standard 95% Conﬁdence R2
[(mg/uL) x 103;[H"-min'l Error Level
Methyl Linoleate -2.77 $0.294 (-3.53, -2.02) 0.964
Methyl Linolenate -3.36 $0.152 (-3.78, -2.94) 0.981

 

Table 4.8 Reaction Rate Constant for the Ozonolysis of Regular Methyl Soyate:
Methyl Linoleate, Linolenate Constituents

 

 

Catalgic Ozonolysis

 

 

 

 

 

 

 

 

 

 

 

Component Estimate of In k Standard 95% Conﬁdence R2
[(mg/pL) x 103]"°‘-min" Error Level
Methyl Linoleate - 95 $0.524 (-4.29, -1.60) 0.886
MethLlLinolenate -2.87 $00736 (-3.07, 266) 0.992
Non-Catalgic Ozonolysis
Component Estimate of In k Standard 95% Conﬁdence R2
[(mg/uL) x 103]I*‘-min" Error Level
Methyl Linoleate -2.11 $0.194 (-2.61, -1.61) 0.971
Methyl Linolenate -2.68 $0.118 (-3.00, -2.35) 0.976

 

Table 4.9 Reaction Order Constant for the Ozonolysis of Low-Sat Methyl Soyate:
Methyl Linoleate, Linolenate Constituents

 

 

Catalgic Ozonolysis

 

 

 

 

 

 

 

 

 

 

 

Component Estimate of a Standard 95% Conﬁdence R2
Error Level
Methyl Linoleate 0.576 $00164 (0.534, 0.618) 0.996
Methyl Linolenate 0.725 $00713 (0.527, 0.923) 0.963
Non-Catalgic Ozonolysis
Component Estimate of a Standard 95% Conﬁdence R2
Error Level
Methyl Linoleate 0.684 $00594 (0.531, 0.836) 0.964
Methyl Linolenate 0.739 $00511 (0.598, 0.881) 0.981

 

88

 

 

 

Table 4.10 Reaction Order Constant for the Ozonolysis of Regular Methyl Soyate:

Methyl Linoleate, Linolenate Constituents

 

 

 

 

 

 

 

 

 

 

 

 

 

Catalgic Ozonolvsis
Component Estimate of a Standard 95% Conﬁdence Rj
Error Level
Methyl Linoleate 0.715 $0.115 (0.420, 1.01) 0.886
Methyl Linolenate 0.605 $00266 (0.531, 0.679) 0.992
Non-Catalgic Ozonolvsis
Component Estimate of a Standard 95% Conﬁdence RT
Error Level
Methyl Linoleate 0.539 $00417 (0431, 0.646) 0.971
Methyl Linolenate 0.528 $00414 (0.413, 0.643) 0.976

 

 

 

 

 

 

Figure 4.13 shows the relative amounts of degradation for each of the unsaturated
constituents. Nearly all of the double bonds of methyl linolenate were decomposed after
3 hours of ozonolysis, with more than a 98% reduction . Likewise, methyl linoleate and
oleate had over 94% and 80% reduction in double bonds, respectively. Thus, the total

amount of double bonds in the mixture were reduced by more than 90% after three hours

 

 

of ozonolysis .
1 a
0 C18:1
08 _ ' C1812
. A C18:3
L? 0.6 - . .
O
0.4 - ‘ . t
O
A
I
0.2 - o
A
I
O l r I A I
0 50 100 150 200

Reaction Time (mins)

Figure 4.13 Relative Amounts of Double Bond Degradation for the Unsaturated

Moieties

89

The concentration of selected products was also determined by GC. Methyl
hexanoate, nonanoate, and dimethyl azelate were the predicted compounds formed based
on the original hypothesis, conﬁrming the direct conversion of oleﬁns to esters via
ozonolysis. The amount of these compounds produced was higher for catalytic
ozonolysis than for non-catalytic ozonolysis. Figure 4.14 shows the amount of these
compounds produced in the catalytic ozonolysis of low-say methyl soyate. Initially,
more dimethyl azelate is formed than methyl nonanoate; but after a reaction time of 120
mins, more nonanoate is formed. Similar observations were also found for the

ozonolysis of regular methyl soyate.

 

     
 
   
  

25

0 Methyl Nonanoate .
20 4 I Dimethyl Azelate

A Methyl Hexanoate
15 -

—s
O
I

U!
l

Concentration (mg/uL) X 103

 

 

 

I I I

0 50 100 1 50 200
Reaction Time (mins)

Figure 4.14 Kinetics for the Catalytic Ozonolysis of Low-Sat Methyl Soyate: Methyl
Hexanoate, Nonanoate and Dimethyl Azelate Ester Products

90

4.4 GC/MS Analysis

All major products of ozonated methyl soyate were identiﬁed based on molecular
weights using GC-MS. Since GC analysis conﬁrmed that the same products were formed
for both ozonated regular and low-sat methyl soyate under catalytic and non-catalytic
conditions, only the catalytic ozonolysis of low-sat methyl soyate will be discussed in
ﬁrrther detail from this point onward. Figures 4.15 and 4.16 show chromatograms of
non-ozonated and ozonated low-sat methyl soyate for 180 minutes, respectively. For
each scan, a mass spectrum was generated and each peak was identiﬁed by molecular
weight. The statistical probability of the match between the experimental and theoretical
mass spectrums for all identiﬁed peaks was above 75%. This number represents the
likelihood of the identiﬁed peaks based on the NIST library database of mass spectrums.
Identiﬁcation of the majority of peaks and their structure are listed in Table 4.11.
Unlabeled peaks in Figure 4.16 indicate that they were unidentiﬁable by the library

database.

91

ﬁt]!

*
1 f 6

 

 

 

 

 

 

3
L JIUUL

Figure 4.15 Chromatogram of Non-Ozonated Low-Sat Methyl Soyate
*Internal Standard

*1

 

 

 

 

Figure 4.16 Chromatogram of Ozonated Low-Sat Methyl Soyate at a Reaction
Time of 180 mins
*Internal Standard

92

Table 4.11 Peak Identiﬁcations and Their Structures for Ozonated Low-Sat Methyl
Soyate at a Reaction Time of 180 mins

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Peak Component Functional Structure Statistical
Group Match
A Hexanal aldehyde W0 93.3%
0
B Methyl Hexanoate ester / Hop/v 94.1%
Methyl Octanoate ester /0 W 90.6%
0
D Nonanal aldehyde W0 87.8%
E 4-Nonenal aldehyde W0 8 5 .20/0
/ O W
F Methyl Nonanoate ester (I; 91.9%
Methyl 3_ / 0 WA 0
G Nonenoate ester 0 87.7/o
/O W
H Methyl Decanoate ester (I) 78.7
*1 Methyl /0\IrVW\/\ 88.1%
Undecanoate ester 0
Methyl 10- ADM 35.1%
I Undecanoate ester 0
’0W
2 Methyl Palmitate ester 0 89.4%
J Dimethyl Azelate ester ’OMO\ o
O
K Methyl 9-OXO- ester /OW
Nonanoate o 922%
/0W
3 Methyl Stearate ester 0 84.2%
4 Methyl Oleate ester ’OW 92.6%
- IOW
5 Methyl Linoleate ester 0 91.5%
x /
6 Methyl Linolenate ester ’OWW 87.7%
0
*Internal Standard

93

Three of the expected esters from the oxidative cleavage of low-sat methyl soyate

by ozone were detected. These products include methyl hexanoate, nonanoate, and

methyl azelate. Figures 4.17-4.19 show the experimental mass spectra (top) for these

esters and their corresponding theoretical mass spectra (bottom) that was generated by the

NIST/EPA/NIH mass spectral library.

 

 

 

 

 

 

ExperimentalMS
MelthylHexanoate 74.0
8
6
%
87.0 990
59.0 '
2 55.0 71-0 l
% .I.1.I -..l..r 82.0. r -- .1 105.0 139.0
m/z 50 60 7'0 so 90 100 110 120 130 140
NlSTMS
H
Methyl exanoate 74. 0
O
87.0
99.0
71.0 I
..']. '..,...!.4ﬁﬁ;l....,-...,.-..1....,.r
70 80 90 100 110 120 130 140

 

Figure 4.17 Mass Spectra of Methyl Hexanoate

94

Three of the expected esters from the oxidative cleavage of low-sat methyl soyate

by ozone were detected. These products include methyl hexanoate, nonanoate, and

methyl azelate. Figures 4.17-4.19 show the experimental mass spectra (top) for these

esters and their corresponding theoretical mass spectra (bottom) that was generated by the

NIST/EPA/NIH mass spectral library.

 

 

 

 

 

 

ExperimentalMS
MelthylHexanoate 74.0
8
%
87.0 990
2 59.0 '
55.0 71.0 I
o .. .th -. . .u..| 82.12 .r - . 11.19542 . .1399. . . . ..
m/z 5'0 ob 7’0 80 90 100 110 120 130 140
NISTMS
Me:hyl Hexanoate 74. 0
O
%
87.0
99.0
71.0 I
.J]. '..,.n.!,....31....,.r..,....,-...,.T
m/z 70 80 90 100 110 120 I30 I40

 

Figure 4.17 Mass Spectra of Methyl Hexanoate

95

ExperimentalMS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Meihleonanoate 74.0
8
% 87.0
40
2 55.0 101,0 129.0 141.0 144.0
59.0 59_o | 172.0
, “In, ..,...1 3.3.9., 3801/, 315-11.,1 , ,l, , , . , ,1, . ,
m/z 60 80 100 120 140 160 180
NISTMS
Methleonanoate
80 /o\n/\/\/\/\
o
60
%
4 87.0
2 55.0 690 , 1010 1290 141.0
$111, -11.: ,r. 6 11.5-o. .r'. it - . -1119, .
m/Z 60 80 100 120 140 160 180
Figure 4.18 Mass Spectra of Methyl Nonanoate
ExperimentalMS
Dimethlo ylAzelate 152.0
80 185.0
143.0
% 55.0 74-0 83.0 111.0
265.1
m/z so 100 150 200 250 300
NISTMS
DimethylAzelate
152.0
10
80 ”'0 74.0 ”1'0 W
83.0
6 143.0 ‘85-0
%
3.0 97.0 124.0
2
171.0
m/z 50 100 150 200 250 300

Figure 4.19 Mass Spectra of Dimethyl Azelate

96

Since the internal standard solution contained only selected esters, the area
percent GC quantiﬁcation method was used to estimate the amount of all the identiﬁable
components in the catalytic, ozonated low-sat methyl soyate mixture that are listed in
Table 4.11. This method assumes that the detector responds identically to all compounds.
However, due to the complexity of the structures in the product mixture, this assumption
is not valid. Thus, this method provides a rough estimate of the amounts of analytes
present. To calculate the area percent, the peak area of an analyte is divided by the sum
of all the peak areas. This value represents the percentage of an analyte in the sample.
The peak area percent divided by 100 is roughly equal to the mass fraction. The area
percents for all components were automatically calculated by the GC integrator. Since
methanol (area percent = 86.72634) and the internal standard (area percent = 1.97269)
were not in the original product mixture, the area percent for the major identiﬁable
components was normalized. The total sum of the peak area percentages for methanol,
internal standard, and the major compounds was about 98%. The ﬁnal mass of the
ozonated mixture after a reaction time of 180 mins, minus the mass of the catalyst, was
determined to be about 141 grams by gravimetrical means. Thus, a rough mass estimate

for each product component can be determined, as shown in Table 4.12.

97

Table 4.12 Mass Estimation for the Major Components in the Catalytic, Ozonated

Low-Sat Methyl Soyate at a Reaction Time of 180 mins

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Peak Component Peak Area Normalized Peak Component Mass
Percent Area Percent in Mixture
(grams)
A Hexanal 0.67235 7.34231 10.35266
B Methyl 0.29255 3.19475 4.50460
Hexanoate
C Methyl 0.35690 3.89748 5.49545
Octanoate
D Nonanal 0.03059 0.33405 0.47101
E 4-Nonenal 0.06597 0.72042 1 .01 579
F Methyl 0.79361 8.66651 12.21978
Nonanoate
G Methyl 3- 0.63 805 6.96774 9.82451
Nonenoate
H Methyl 0.07138 0.77950 1.09910
Decanoate
I Methyl 10- 0.07553 0.82482 1.16300
Undecanoate
2 Methyl 0.80435 8.78380 12.38516
Palmitate
J Dimethyl 0.60593 6.61698 9.32994
Azelate
K Methyl 9- 2.19400 23.95923 33.78251
Oxo-
Nonanoate
3 Methyl 0.55520 6.06299 8.54882
Stearate
4 Methyl Oleate 1.12714 12.30878 17.35538
5 Methyl 0.83324 9.09929 12.82999
Linoleate
6 Methyl 0.04041 0.44129 0.62222
Linolenate

 

 

 

 

 

 

Unlike in the FTIR and NMR analysis, which were conducted at room
temperatures, no hydroperoxides or ozonides were detected by GC or GC/MS in the
ozonated oil. Most hydroperoxides become unstable at temperatures above 70°C [34].
Due to the GC column temperature increasing at a scanning rate of 5°C/min from an

initial temperature of 50°C up to a ﬁnal temperature of 240°C, the hydroperoxides and

98

ozonides present in the ozonated fuel were most likely thermally decomposed during the
GC/MS analysis. The main decomposition products include aldehydes and carboxylic
acids. For ozonides, the driving force for its decomposition is the cleavage of the energy-
rich O-O bond and the release of conformational strain present in the trioxolane ring [34].
Components present in the corresponding volatile fraction were also identiﬁed by
GC/MS. Figure 4.20 shows the chromatogram for the volatile fraction of ozonated low-
sat methyl soyate, which corresponds to the oil fraction presented in Figure 4.16. Table
4.13 lists the identiﬁed compounds and their corresponding structures. The statistical
probability of the match between the experimental and library database mass spectrums
for all identiﬁed peaks was above 70%. Unlabeled peaks in Figure 4.20 indicate that they
were unidentiﬁable by the library database. The aldehydes formed were also the volatile
products formed in the ozonation of sunﬂower oil [121]. Moreover, 1,1,3,3-
Tetramethoxy-Propane (peak 1) and Methyl, 3-3-Dimethoxy-Propionate (peak 7) are the
derivative forms of dimethyl malonate that were present in the volatile fraction.
Dimethyl malonate is one of the predicted esters that is theoretically formed from the

oxidative cleavage of methyl linoleate and linolenate.

99

44
j

 

 

 

 

5 8 15
UL 67 9 1'0“ LL..._L§_____,1.41 16

 

Figure 4.20 Chromatogram of Ozonated Low-Sat Methyl Soyate at a Reaction
Time of 180 mins: Corresponding Volatile Fraction

100

Table 4.13 Peak Identifications and Their Structures for Ozonated Low-Sat Methyl

Soyate at a Reaction Time of 180 mins: Volatile Fraction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Peak Component Functional Structure Statistical
Group Match
\
1 1,1,3,3-Tetramethoxy- acetal /O W0 70%
Propane / O O \
2 Hexanal aldehyde W0 89.6%
. /O
3 1 ,1 -D1methoxy- ace tal W 82.7%
Hexane /O
/O \/\/\/
4 Methyl Hexanoate ester (II) 93.1%
. /O
5 I’I‘D‘mﬂ’m‘y' acetal W 83.6%
Heptane ,0
6 1,1-Dimethoxy- ace tal ’OW 81 4%
Octane /O '
/OWO\
7 Methyl,3,3- ester 77 8%
Dimethoxy-Propionate /O O '
- - - /0
8 1 ,1 DlmethOXy acetal W 75 .7%
Nonane ,0
/O W
9 Methyl Nonanoate ester (I) 88.3%
10 Methyl Decanoate ester C") 73.7%
HO WV
11 Hexanoic acid acid (lj 77.1%
12 Methyl Undecanoate ester (I) 33.5%
H
1 3 Phenol alcohol 84. 1%
14 Methyl Palmitate ester /OW 76.1%
0
0
15 Dimethyl Azelate ester ’OMO\ 88'] /°
0 O
15 Methyl Stearate ester ’OW 85.6%

 

 

 

 

 

101

 

Many of the major products present in the volatile fraction were acetals. One
possibility of their formation is the reaction of aldehydes with methanol under acid
catalytic conditions. The overall reaction mechanism, illustrated in Figure 4.21, proceeds
in four stages. The hemiacetal is formed in the ﬁrst stage by nucleophilic addition of the
alcohol to the carbonyl group (1). Under the acidic conditions of its formation, the
hemiacetal is converted to an acetal by way of a carbocation intermediate (2). This
carbocation is stabilized by electron release from its oxygen substituent (3). Finally,
nucleophilic capture of the carbocation intermediate by an alcohol molecule leads to an
acetal (4). Hexanoic acid, a carboxylic acid, was formed in the volatile fraction. Thus, it
may serve as the acid that catalyzed the reaction of acetal formation. This carboxylic
acid may have been formed by the hydrolysis of the secondary ozonide (refer to Figure

1.6); or by ester hydrolysis, shown in Figure 4.22.

102

+

o + :OH , 0H + OH
[I 2.. ll R_0_H, I —_H. |
RCH *— RCH ‘—— Rcle ‘— R(|3H

Ald O ’
ehyde ()‘P \ OR
H R’ Hemiacetal
H H
0.. \g/
I H+ LI R\+ /H
RCH —-> RCH —-> C + H O
l ‘— | ‘_‘ l 2
OR’ OR’ OR’ Water
Hemiacetal Carbocation
R + /H R /H
‘1’ ._. ‘1
493’ +9.1?
H R’ ,
R H \.+./ °R
R’ \ / (>0 I
\ . C _, _. RCH
H / +0 R9 RCIJH 0R9
° ' ’ A t 1
Alcohol OR ce a

Figure 4.21 Overall Reaction Mechanism for Acetal Formation

O 0

II II

RCOR’ + H2O _.. RCOH + R’OH

Ester Water Carboxylic Alcohol
Acid

Figure 4.22 Hydrolysis of Ester

103

(1)

(2)

(3)

(4)

Similar products formed in the ozonation of methyl soyate were also formed in
the autoxidation of pure methyl oleate, linoleate, and linolenate [122, 123]. The volatile
by-products produced during the autoxidation of methyl oleate, linoleate, linolenate,
under the inﬂuence of metallic promoters was studied [122]. The components of the by-
products were separated and identiﬁed by GC/MS. Air or oxygen was bubbled through
the methyl esters containing the desired amount of promoter via a gas washing bottle at
20°C for 10 hours. The volatile by-products were collected in a cryogenic trapping
system. Table 4.14 lists some of the autoxidation volatile by-products derived from the
three esters. In a similar study conducted by Frankel et al. [123], pure hydroperoxides
from autoxidized methyl oleate, linoleate, and linolenate were thermally decomposed and
the major volatile products were identiﬁed. The GC/MS analysis of volatile compounds
from thermally decomposed hydroperoxides are presented in Table 4.15. This work also
supports the fact that hydroperoxides of ozonated methyl soyate were thermally
decomposed during GC/MS analysis, based on the similarity in product distribution.

Table 4.14 Products Formed During the Autoxidation of Methyl Oleate, Linoleate,
and Linolenate in the Present of Metallic Promoters“

 

 

 

 

Methyl Oleate Methyl Linoleate Methyl Linolenate

Cobalt/lead Cobalt/lead Cobalt/Aluminum Cobalt/lead Cobalt/aluminum
propanal hexanal hexanal propanal propanal
hexanal 2-hexenal methyl hexanoate methyl methyl octanoate

octanoate
octanal hexanoic methyl 2-pentenal 2-pentenal
acid heptanoate
nonanal methyl methyl octanoate
octanoate

 

 

 

“Source: Ref. [122]

104

Table 4.15 Volatile Compounds of the Thermally Decomposed Pure Hydroperoxides
from Autoxidized Methyl Oleate, Linoleate, and Linolenate“

 

 

 

 

 

MethLlOleate Methyl Linolegtg Methyl Linolenate
Compound Weight % Compound Weight % Compound Weight %
octanal l 1 hexanal 15 propanal 7.7
nonanal 15 2-nonenal 1.4 decatrienal l4
methyl 9-oxo- 15 methyl 9- l9 methyl 9-oxo- l3
nonanoate oxo- nonanoate
nonanoate .
methyl 5 methyl 15 methyl 22
octanoate octanoate octanoate
methyl 1.5 2,4- 9.3
nonanoate heptadienal
methyl 10- 12
oxo-decanoate

 

 

 

 

“Source: Ref. [123]

Based on these studies, major products formed in the ozonolysis of methyl soyate
may be attributed to autoxidation from oxygen in the 03/02 gaseous mixture. To conﬁrm
this hypothesis, regular biodiesel, in the presence of methanol and calcium carbonate as
the catalyst, was oxidized with oxygen for 180 mins, using the same experimental set-up
and conditions employed in the ozonolysis experiments. The GC Chromatogram of the
oxidized oil is illustrated in Figure 4.23. The double bond decomposition comparison
between the autoxidation and ozonolysis of biodiesel is depicted in Table 4.16. Like in
the ozonolysis experiments, the volatile products of autoxidized methyl soyate were
collected and analyzed. Figure 4.24 shows the chromatograrn of the volatile fraction
from autoxidized regular methyl soyate, where Table 4.17 lists the compounds and
structures for each identiﬁable peak. Indeed, many of the same products from the
ozonation experiments were formed in the autoxidation experiments. The amount of

double bond decomposition was signiﬁcantly lower when ozone was not used as the

105

primary oxidant. Thus, it may be deduced that ozone was simultaneously inducing lipid
oxidation (ozone-induced oxidation) and oxidatively cleaving the alkene moiety
(ozonolysis) of biodiesel during the oxidation experiments. In fact, in addition to the use
of ozone as the primary oxidant in the synthesis of a range of oxygen-containing
functional groups, there are many applications in which ozone serves only as a catalyst or

initiator for another oxidant, usually oxygen [124-126].

:3

3
IL IL AUUL

Figure 4.23 Chromatogram of the Autoxidation of Regular Methyl Soyate at a
Reaction Time of 180 mins

 

 

 

 

 

 

 

 

 

Table 4.16 Double Bond Decomposition Comparison Between the Autoxidation and
Ozonolysis of Regular Methyl Soyate

 

 

Component C/Co C/Co
Autoxidation Ozonolysis

Methyl Oleate 0.8253 0.2184

Methyl Linoleate 0.8031 0.0764

Methyl Linolenate 0.6703 0.0259

 

106

12
M__

3

J

 

 

‘L__l

6

L‘AA. ~— A

7’}.

Figure 4.24 Chromatogram for the Autoxidation of Regular Methyl Soyate at a
Reaction Time of 180 mins: Volatile Fraction

Table 4.17 Peak Identiﬁcations and Their Structures for the Autoxidation of
Regular Methyl Soyate at a Reaction Time of 180 mins: Volatile Fraction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Functional . .
Peak Component Group Structure Statistlcal
Match
1 Hexanal aldehyde NW0 88.3%
- /O
2 1,1-D1methyoxy ace tal W 87.2%
Hexane /Q
. /0W
3 1,1-1221111320“ acetal 74%
/O
/O
4 Methyl ester W 72%
Decanoate O
/ 0 W
5 Methyl ester II 91 . 1%
Undecanoate 0
/O\r\/\/\/\/\/\/\/
6 Meti‘yl ester I 85.6%
Palmltate 0
/0W
7 Methyl Oleate ester 74.2%
0
/ \
/
8 Methyl ester 0W 73.4%
Lmoleate O

 

107

 

Chapter 5

Results & Discussion Part 11:
Thermal Analysis

5.1 TGA Analysis

Volatility is one of the most fundamentally important qualities of fuel in engines
because it has a major affect on the vapor-air ratio in the cylinder and, therefore,
inﬂuences the ignition quality of the fuel. The TGA proﬁles of ozonated low-sat methyl
soyate, at various reaction time intervals, and No.2 diesel fuel are illustrated in Figure
5.1. It is clearly evident that as the reaction time increases, the volatility of the ozonated
biofuel approaches that of the No. 2 diesel fuel. In general, the boiling points of methyl
esters increase with the length of the hydrocarbon tail, or with molecular weight. Methyl
soyate has a rather low volatility due to the presence of both C16 and C18 hydrocarbons.
However, its volatility becomes comparable to No. 2 diesel fuel after ozone-mediated
oxidation, as the heavy, long chain, unsaturated and saturated components are fragmented
to shorter, lighter, components. Also, as in the GC/MS experiments, the hydroperoixdes
and ozonides present in the ozonated fuel were thermally decomposed during the TGA
experiments as the analysis temperature reached a maximum at 350°C. Thus, the
decomposition products of hydroperoxides and ozonides seemed to improve the volatility
of ozonated methyl soyate. Table 5.1 lists the available boiling points [127] and
molecular weights of the products present in ozonated methyl soyate. Methyl palmitate
and stearate have the highest boiling points due to their degree of saturation and the
length of their hydrocarbon tails. Likewise, the unsaturated constituents also have

relatively high boiling points compared to the formed products.

108

  
 
  
 
 
 
  

100 -

 

 

— 0 mins
— 30 mins
80 " —60 mins
g? - 90 mins
:1 6O _ — 120 mins
E — 150 mins
3 - 180 mins
.g 40 J — No. 2 Diesel
3
20 -
0 I I I *1
0 100 200 300 400

Temperature (°C)

Figure 5.1 TGA Profiles of Ozonated Low-Sat Methyl Soyate and No. 2 Diesel Fuel

Table 5.1 Boling Point Data for Compounds Present in Ozonated Methyl Soyate

 

 

 

 

 

 

 

 

 

 

 

Product Molecular Boiling Point Product Molecular Boiling Point
Weight °C Weight °C
Methyl 298.50 443 Nonanal 142.26 191
Stearate
Methyl 270.45 417 Methyl 292.46 182
Palmitate Linolenate
Methyl 10- 198.30 248 Dimethyl 216.28 156
Undecenoate Azelate
Methyl 186.29 224 Methyl 130.19 150
Decanoate Hexanoate
Methyl 296.49 219 Hexanal 100.16 131
Oleate
Methyl 294.48 215 4-Nonenal 140.22 N/A
Linoleate
Methyl 172.27 214 Methyl 3- 170.25 N/A
Nonanoate Nonenoate
Methyl 158.24 193 Methyl 9-Oxo- 186.25 N/A
Octanoate Nonenoate

 

 

 

 

 

109

 

The derivative weight loss, or the maximum rate of weight change, versus
temperature data for ozonated methyl soyate and No. 2 diesel fuel is illustrated in Figure
5.2. For non-ozonated methyl soyate (0 mins), one maximum peak occurs at around
210°C, which is due to the presence of the starting methyl esters. As the reaction time
increases, however, a second maximum develops at around 145°C, which corresponds to
the production of the lower-molecular weight esters and aldehydes. Moreover, the peak
at 210°C decreases as a function of reaction time, supporting the fact that the starting
methyl esters are being cleaved during ozonolysis. One broad maximum peak occurs at
around 150°C for No. 2 diesel fuel. Thus, after 3 hours of ozonation, the derivative
weight loss vs temperature proﬁle of ozonated methyl soyate is comparable, almost

identical, to that of No. 2 diesel fuel.

  

 

 

 

3 -
a —0 mins
°\ 25 - --30 mms
..\° —60 mins
7;; —90 mins
8 2 " — 120 mins
:1. — 150 mins
Eu 1 5 ' -— 180 mins
g --No. 2 Diesel
0 1 "
.2.
E"
E 0.5 ‘
Q
0 ' l l
O 100 200 300 400

Temperature (°C)

Figure 5.2 Plot of Derivative Weight Loss vs Temperature for No. 2 Diesel Fuel and
Ozonated Methyl Soyate

110

TGA experiments were conducted with ozonated regular methyl soyate to
compare its TGA proﬁle with that of ozonated low-sat methyl soyate. Figure 5.3 shows
the results of these experiments. As expected, the peak area of the ﬁrst peak is greater in
regular methyl soyate than in low-sat methyl soyate. This observation can be explained

by the fact that the amount of saturation in low-sat methyl soyate is about half of that in

regular methyl soyate.

 

 

 

 

 

 

3.5 -
6 0 mins
°\ 3 - Regular
é ﬂ
3 2'5 - LowSat
C
A 2 ..
E
.2”
g 1'5 ' 180 mins
0 ,
.2 1 ‘
E5
.2
33 0.5 ‘
Q

0 ' I
0 100 200 300 400
Temperature (°C)

Figure 5.3 Plot of Derivative Weight Loss vs Temperature for Regular and Low-Sat
Methyl Soyate

111

5.2 DSC Analysis

Thermograms of low-sat methyl soyate and ozonated low-sat methyl soyate at
various reaction times are compared in Figure 5 .4. The cooling curves for both fuels
display two major exothermic regions: region 1 between -10°C and -15°C, and region 2
less than -65°C. This behavior is consistent with mixtures of fatty compounds, such as
unsaturated and saturated methyl esters [128]. The length of the hydrocarbon chains and
their degree of unsaturation strongly influence the phase transitions of fatty mixtures.
Components with short-chain hydrocarbons will crystallize at a lower temperature than
components with long—chain hydrocarbons because the intermolecular forces are weaker
between the shorter fatty tails. Intermolecular forces among neighboring hydrocarbon
tails increase as the tails get longer, enhancing the tendency to crystallize. In terms of
saturation, saturated components are ﬂexible since every carbon-carbon bond is free to
rotate, forming closely packed and well-ordered crystals. Because rotation around the
double bond is hindered, the presence of cis double bonds produces a distinct bend in the
hydrocarbon chain. This bend prevents the formation of closely packed, well-ordered
crystals and, hence, decreases the intermolecular forces amongst the hydrocarbon chains.
Consequently, cis unsaturated fatty esters have much lower freezing points than saturated
fatty esters. Thus, unsaturation present in methyl esters has a pronounced lowering effect
on freezing points, and polyunsaturation more so than monounsaturation [129]. For
thermograms of low-sat methyl soyate and ozonated methyl soyate, the higher
temperature region (region 1) is the freezing transition of the high molecular weight,
long-chain saturated methyl esters, and the lower temperature region (region 2) is the

freezing transition of the unsaturated and low-molecular weight methyl esters. The

112

available freezing point data [127] for compounds found in ozonated methyl soyate is

presented in Table 5.2.

 

 

3.75
[b
0 3° 3 Region 1
E 3 180
g E 2 25 50 mins
*5 g 120 mins
:33 1;; 1.5 90 mins
:55 60 mins
0.75 30 mins
0 mins
0
-100 -80 -60 -4O -20 0 20 40
Temperature (°C)

Figure 5.4 DSC Cooling Thermograms for Low-Sat Methyl Soyate

Table 5.2 Freezing Point Data for Compounds Present in Ozonated Methyl Soyate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Product Molecular Freezing Product Molecular Freezing
Weight Point Weight Point
°C °C
Methyl 298.50 40 Methyl 10- 198.30 -28
Stearate Undecenoate
Methyl 270.45 30 Dimethyl Azelate 216.28 -20
Palmitate
Methyl 130. 19 -71 Methyl Oleate 296.49 ~20
Hexanoate
Hexanal 100.16 -56 Methyl Decanoate 186.29 -18
Methyl 158.24 -40 Nonanal 142.26 N/A
Octanoate
Methyl 292.46 below -35 4-Nonenal 140.22 N/A
Linolenate
Methyl 294.48 -35 Methyl 3- 170.25 N/A
Linoleate Nonenoate
Methyl 1 72.27 -30 Methyl 9-Oxo- 1 86.25 N/A
Nonanoate Nonenoate

 

113

 

Figure 5.5 shows the onset crystallization temperatures for regions 1 and 2 of
ozonated low-sat and regular methyl soyate and Table 5.3 list these values. The onset
crystallization temperature, Tc], was deﬁned as the intersection of a line tangent to the
scan at the point of sharpest slope and a line tangent to a baseline segment on the “hot”
side of the onset crystallization peak. Similarly, the onset freezing temperature, Tcz, was
deﬁned as the point where a line tangent to the scan at the point of sharpest slope on the
“hot” side of the freezing peak intersects a line across the base of the region. The regular
methyl soyate thermogram, TCI = 379°C, is comparable to that of unwinterized methyl
soyate, TCI = 37°C, of Lee et. al.[l30]. It is clearly evident that TC; has been
signiﬁcantly reduced from about -62°C (for methyl soyate) to a minimum temperature of
about -87°C. This phenomenon occurred because of the cleavage of the double bonds,
which reduced the length of the hydrocarbon tail, into smaller fragments and the
formation of methyl and dimethyl esters at the terminal position, as predicted. Also, the
size of the peak diminished due to the reduction of the unsaturated portion of the oil.
After 180 min of reaction time, there was nearly no phase transition occurring in region
2. Also, as expected, the onset crystallization properties in region 1 is lower for low-sat
methyl soyate that for regular methyl soyate.

Note that there was a slight increase in both Tel, and Tcz starting at a reaction
time of 60 min. This observation may be due to the presence of monomeric and
polymeric ozonides from the ozonated unsaturated moieties of methyl soyate. In general,
monomeric and polymeric ozonides are oily, viscous liquids with a characteristic odor,
which rapidly decompose at temperature above 70°C; at room temperature most of them

are quite stable [34]. Moreover, depending on the structure of the initial oleﬁn and the

114

reaction conditions, monomeric and polymeric ozonides can be viscuous and Vaseline-
like (ozonides of normal oleﬁne), rubber-like (ozonides of cyclo-oleﬁns), or powder form
(ozonides of naphthalene, phenanthrene). Oleﬁn ozonides have not been studied very
thoroughly and, thus, physicochemical properties have been described only for individual
representatives. A comparison of the physicochemical properties of the monomeric and

polymeric ozonides of cyclohexane is presented in Table 5.4.

 

 

 

 

A 20
CE), Region 1, TC,
0) g I
5 0 1‘ ' - . : o o
‘3 0 O 0 °
0)
g -20 ~
<1)
2 0 Low-Sat
‘9 -40 _ II Re ular
.g Region 2, Ta g
E -60 3
5 :
+5 '80 T . u . .
g I
O

-100 . T r r r I

0 3O 6O 90 120 150 180 210

Reaction Time (mins)

Figure 5.5 Onset Crystallization Temperatures for Regions 1 and 2 as a Function of
Reaction Time

Table 5.3 Onset Crystallization Temperatures for Methyl Soyate

 

 

 

Reaction Time Low-Sat, TCI Low-Sat, Tcz Regular, Tc] Regular, Tcz
(minS) (°C) (°C) (°C) (°C)

0 -9.40 -6l.75 -3.79 -62.24
30 -9.06 -72.44 —4.72 -76.24
60 -8.57 -87.91 -3.56 -86.55
90 -7.42 -83.98 -2.60 -83.73
120 -5.66 -82.41 -l.23 -81.88
150 -5.37 -80.94 1.30 -80.42
180 -5.50 -78.91 1.87 -79.08

 

 

 

 

 

 

115

Table 5.4 Physicochemical Properties of Cyclohexene Ozonides

 

Ozonide Monomeric Polymeric

 

Structure ,0—0\ ,0—0\
" CH2CH2 CH CHCHZCHZ- CHZCHZ CH CHCH2CH2
‘ O ’ ‘ O ’ x

 

 

 

 

 

 

 

 

Appearance colorless liquid white elastic substance
Freezing Point, °C -38 72
Boiling Point 32 not volatile
IR-Spectrum
Absorption 11 10 l 110

 

5.3 Low-Temperature Flow Properties
5.3.1 Cloud, Pour, and Cold Filter Plugging Point Measurement

Selected low-temperature ﬂow properties were evaluated for low-sat methyl
soyate and ozonated low-sat methyl soyate. Shown in Table 5.5, these measurement
values were compared to literature measurements of regular methyl soyate and No. 2
diesel fuel. The properties for low-sat methyl soyate were lower than regular soyate, as
expected. However, the cold-properties for the ozonated fuel were not enhanced,
probably due to the presence of viscous, oil polymeric and monomeric ozonides. Thus,
further product puriﬁcation must be considered in order to separate out the ozonides from
the product mixture. Eliminating the ozonides should signiﬁcantly improve the cold-
temperature ﬂow properties.

Table 5.5 Low-Temperature Flow Properties of Methyl Soyate and No. 2 Diesel Fuel

 

Methyl Low-Sat Low-Sat Ozonated No. 2
Soyate“ Methyl Soyate Methyl Soyate Diesel“

 

 

 

 

Cloud Point, °C 0 -4 3 -16
Pour Point, °C -2 -6 O -23
Cold Filter -3 -10 9 -27

 

 

 

 

 

Plugging Point, °C

 

“Source: Ref. [131]

116

5.3.2 Viscosity Measurement

The dynamic viscosity of selected oil samples were measured as a function of
shear rate and temperature. All oil samples exhibited Newtonian-like behavior, in which
the plot of shear stress (Pa) vs. shear rate (US) was linear with a slope equal to the
viscosity, illustrated in Figure 5.6. Table 5.6 lists the viscosity of selected samples at
25°C with the corresponding coorelation coefficient (R2) from the linear plot. The
visocity of methyl soyate is about 1.6, or approximately ~2, times the viscosity of No. 2
diesel fuel, which is comparable to literature data. The viscosity of ozonated methyl
soyate has about the same viscosity as its parent triglyceride and is about 14 times more
viscous than No. 2 diesel ﬁrel. Figure 5.7 shows the dependence of viscosity on
temperature for low-sat methyl soyate. The viscosities decrease with rising temperature
as expected and follow an exponential behavior. However, the viscosity of the ozonated
methyl soyate is signiﬁcantly higher than that of methyl soyate. Thus, the presence of
viscous/oily ozonides has a profound effect on the viscosity of the ozonated fuel.

Table 5.6 Dynamic Viscosity Values of Selected Oils at 25°C

 

 

 

 

 

 

 

 

 

Oil/Fuel Viscosity R2
Pa-s

Low-Sat Soybean Oil 0.0503 0.9997

Low-Sat Methyl Soyate 0.0060 0.9927

Ozonated Low-Sat Methyl Soyate 0.0519 0.9993

No. 2 Diesel Fuel 0.0038 0.9909

 

117

 

 

 

 

 

 

 

 

 

 

10 50
I LowSat Methyl Soyate
0 Reg Methyl Soyate
8 " A Diesel Fuel ' 40
E X 02 LowSat Methyl Soyate * g
v a
a 6 - - 30 e
v :13
C2 ‘8‘ III-- §
'5 4 " .. ',oo°0° ’ 20 m
G) I I...0.0 Q
a I .° ° AA“‘ 3
I..::.. a “A
.I,o° AA A L 10
..’I00 “A“
«urrnum
I I I 0
400 600 800 1000
Shear Rate (Us)
Figure 5.6 Shear Stress Versus Shear Rate for Selected Fuels
*Data on secondary y-axis
0.120
K I Ozonated- - - -
7;; 0-100 " \ 0 Non-Ozonated
53 \
g 0 080 J \ \
x
g 0.060 - x
> \‘\
O \
E 0.040 - \ \ \
s. \‘
Q 0.020 '
0.000 . . ' . a
0 10 20 30 50
Temperature (°C)

Figure 5.7 Dynamic Viscosity as a Function of Time for Low-Sat and Ozonated

Low-Sat Methyl Soyate

118

Chapter 6
Conclusions, Future Work & Biodiesel Research Considerations

6.1 Conclusions

Important current trends in the chemical industry are intensiﬁcation of production
processes and reduction of the volume of by-products, and of harmful liquid-gas
discharge. In chemical manufacturing, the various oxidation operations are common in
which gaseous oxygen or inorganic oxidants are employed as the oxidizing agent. One of
the promising methods for manufacturing many products of industrial importance is
utilization of ozone as the oxidizing agent. Ozone reacts more energetically than any
other oxidizing agents and, moreover, it excludes formation of large amounts of inorganic
waste matter, whose separation from the reaction products and subsequent utilization
involve sizable additional costs. Ozone’s most characteristic and, at the same time, very
important use in the chemical industry and preparative chemistry, results from its speciﬁc
effect on the oleﬁnic double bond. Ozonolysis reactions are also frequently employed
during a synthetic pathway, as ozone reacts under remarkably mild conditions and
displays a high level of selectivity, making ozonolysis an extremely valuable synthetic
entity. The ﬁrst ozonolysis process commercialized was the production of azelaic and
nonanoic acids from oleic acid, which was introduced by Emery Industries [132].
6.1.1 Structural Analysis

F TIR and GC/MS analysis conﬁrmed that the double bonds in methyl soyate were
successfully cleaved by ozone-mediate oxidation. The total amount of double bonds in
the mixture was reduced by more than 90% after three hours of ozonolysis. The

degradation rate of methyl linolenate was approximately three times faster than that of

119

methyl linoleate. Methyl palmitate, stearate, and oleate all ﬁt zero-order reaction
kinetics. The kinetic studies also suggest that the rate of ozone-mediated oxidation of
biodiesel is inﬂuenced by the amount of double bonds and steric effects inherent in its
molecular structure.

F TIR and 1H NMR conﬁrmed the presence of hydroperoxides and ozonides in the
ozonated fuel. However, they thermally decomposed during the GC/MS analysis, leading
to the production of additional methyl esters. Hydroperoxide formation may be the result
of water, a by-product in the conversion of both the hemiacetal and hydroperoxide
intermediates to methyl esters, reacting with the secondary ozonide. This particular
reaction readily occurs without the necessity of a catalytic acid or base. Another possible
route for hydroperoxide production is the reaction of the carboxyl oxide intermediate
with the protic solvent. Thus, there are several competing reactions occurring during the
ozonation of methyl soyate. Ozonide formation is most likely due to the steric hindrance
of the methyl soyate molecule, which is composed of long-hydrocarbon chains. Based on
the FTIR absorption intensities, the ozonide was more concentrated in the volatile
fraction than in the oil fraction. The volatile fraction of the ozonated fuel were collected
in a dry-ice collection trap and characterized by FTIR and GC/MS. The majority of the
volatile by-products were acetals. Acetal formation can occur by the reaction of alcohol
with an aldehyde under acidic conditions. Small amounts of carboxylic acids, like
hexanoic acid, could have served as the acidic medium.

Three of the ﬁve expected esters, methyl hexanoate, nonanoate, and azelate, were
formed during the ozonation experiments. Two derivative forms of dimethyl malonate

were detected in the volatile fraction. Methyl propionate was not detected in the GC

120

analysis. Since methyl propionate is a very volatile compound, it may have eluted off the
GC column with the solvent peak, making it undetectable. These results demonstrate
that a co-solvent, like dichloromethane, and very low reaction temperatures are not
needed to form the expected esters, which is a huge advantage from an engineering point
of view.

Similar products were formed in the ozonation and autoxidation of methyl soyate.
It was also found that the amount of double bond degradation was signiﬁcantly lower
when ozone was not the primary oxidant. Thus, it was concluded that ozone was
simultaneously inducing lipid oxidation (ozone-induced oxidation) and oxidatively
cleaving the alkene moiety (ozonolysis) of methyl soyate. In fact, in addition to the use
of ozone as the primary oxidant in the synthesis of a range of oxygen-containing
functional groups, there are many applications in which ozone serves only as a catalyst or
initiator for another oxidant, usually oxygen [124-126].
6.1.2 Thermal Analysis

According to TGA analysis, the volatility of methyl soyate became comparable to
that of No. 2 diesel fuel after 3 hours of ozone-mediated oxidation. The heavy, long
chain, esters were fragmented to shorter, lighter, saturated components, shifting its TGA
proﬁle towards diesel fuel. Also, as in the GC/MS experiments, the hydroperoixdes and
ozonides present in the ozonated fuel were thermally decomposed during the TGA
experiments as the analysis temperature reached a maximum at 350°C. Thus, the
decomposition products of hydroperoxides and ozonides seemed to improve the volatility
of ozonated methyl soyate. Two maxima occur for the rate of weight change data of

ozonated methyl soyate The ﬁrst maximum occurred at 210°C from the presence of the

121

long, hydrocarbon chains of the starting esters and the second maximum occurred at
14°5C from the presence of more volatile products formed after ozonation. One broad
maximum occurred at about 150°C for No. 2 diesel fuel. Therefore, aﬁer 3 hours of
ozonation, the derivative weight loss vs. time proﬁle of ozonated methyl soyate was
comparable, almost identical, to that of No. 2 diesel fuel.

The DSC cooling curves for methyl soyate exhibited two major exothermic
regions: region 1 between -10C and -15C and region 2 under -65C. The higher region (1)
is the freezing transition of the high, molecular weight, long-chain saturated methyl esters
and the lower temperature region (2) is the freezing transition of the unsaturated and low-
molecular weight methyl esters. There was a slight increase in both TCI and Tc;
beginning at a reaction time of 60 mins. This observation may be due to the presence of
monomeric and polymeric ozonides in the fuel, which are generally viscous/oily and
stable at room temperature. Furthermore, TC1 is lower for low-sat methyl soyate than for
regular methyl soyate.

Selected low-temperature ﬂow properties- cloud point, pour point , cold ﬁlter
plugging point, viscosity-were evaluated for methyl soyate. However, these properties
were not enhanced for the ozonated fuel because of the presence of ozonides in the
product mixture. Thus, separation techniques must be developed for their removal from
the product mixture. Eliminating the ozonides should signiﬁcantly improve these

properties.

122

6.2 Future Work
6.2.1 Ozonide Analysis

Common techniques used to analyze ozonides are TLC and HPLC [114]. It is
recommended that HPLC/MS be used to identify and quantify ozonides present in the
product mixture. One advantage of using HPLC over GC is that the analysis is conducted
at room temperature, thus thermal decomposition of the ozonides is avoided. Also, it is
recommended that separation techniques be developed to isolate the ozonide from the
product mixture and reevaluate the structural and thermal properties.
6.2.2 Process Development and Mass Transfer Studies

There are two techniques in which ozone is delivered to a solution during
ozonolysis: diffuser and venture injector. A bubble diffuser, which was used in the
ozonation of methyl soyate, works by emitting ozone through hundreds of bubbles
beneath the solution surface. This results in low ozone mass transfer rate, typically
around 10-15%. Conversely, a venturi injector works by forcing the reaction solution
through a conical body which initiates a pressure differential between the inlet and outlet
ports. This creates a vacuum inside the injector body, which initiates ozone suction
through the suction port. The venture injector system allows very high ozone mass
transfer rate, up to 90%. The increased mass transfer efﬁciency provided by the venturi
injector, combined with the closed nature of the contactor, allows for more precise ozone
dosing and reduces the volume requirements of the contactor. The ozone gas actually
becomes a part of the reaction solution at the venturi, traveling through the contactor
without exposure to air or atmospheric pressure. This adds to the efficiency of the system

'by allowing for greater ozone saturation.

123

It is recommended that a venturi injector assembly be designed and used for the
deliver of ozone during ozonation experiments. Comparative ozone mass transfer studies
between the two different deliver systems should be conducted to understand the effects
of diffusion on the overall rate of reaction.

6.2.3 Quality Assurance Testing for Reliable Vehicle Operation

A precondition for the successﬁrl use of plant oil methyl ester as an alternative
fuel for car and commercial vehicle diesel engines is that they must run just as reliably as
on diesel fuel. If this alternative fuel is to have a long-term future on the market, it must
be able to fulﬁll the same requirements currently met by standard commercial diesel ﬁre],
i.e. it must supply a high quality product. It is recommended that, after further research
in product and process development, the properties comprised in the ASTM D 6751 fuel
standard (Table 6.1) should be evaluated for ozonated biofuel. Engine performance and
emission tests should also be conducted

Table 6.1 ASTM D 6751 Fuel Speciﬁcations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Property ASTM Method Limits Units
Flash Point D93 130 min. C

Water & Sediment D2709 0.050 max. % vol
Kinematic D445 1.9-6.0 mmZ/sec
Viscosity, 40C

Sulfated Ash D874 0.020 max. % mass
Sulfur D5453 0.050 max. % mass
Copper Strip D130 No. 3 max

Corrosion

Cetane Number D613 47 min.

Cloud Point D2500 Report C

Pour Point D97 Report C
Carbon Residue D4530 0.050 max. % mass
Acid Number D664 0.80 max mg KOI-I/g
Free Glycerin D6584 0.020 max. % mass
Total Glycerin D6584 0.240 max % mass
Phosphorus Content D4951 0.001 max. % mass

 

 

 

 

124

 

6.3 Other Uses of Biodiesel Fuel

In addition to serving as fuels, esters of vegetable oils and animal fats can be
utilized for numerous other purposes. Methyl esters can serve as intermediates in the
production of fatty alcohols from vegetable oils [133]. Fatty alcohols are used in
surfactants and cleaning supplies. Branched esters of fatty acids are used as lubricants, in
which their improved biodegradability makes them environmentally attractive. Biodiesel
can also be used as a substitute for home heating oil [134].

Over the past few years, industry knowledge and awareness of methyl soyate as
an alternative industrial solvent has grown tremendously. Methyl soyate possesses good
solvent properties, which is demonstrated by its use as a medium for cleaning beaches
contaminated with crude oil [135-137]. It offers natural cleaning and degreasing
characteristics with low volatile organic compounds (V OCs), low hazardous air
pollutants, low toxicity, high ﬂash point, and it is readily biodegradable. The solvent
strength of methyl soyate is also demonstrated by its high Kauri-Butanol value (relating
to the solvent power of hydrocarbon solvents), which makes it similar or superior to
many conventional organic solvents. The only physical disadvantages of methyl soyate
may be slow evaporation and water insolubility, which can be improved by formulation
with surfactants and co-solvents to meet desired performance requirements. The good
technical attributes of methyl soyate, in combination with the regulatory pressures on the
traditional chlorinated and petroleum solvents, present good opportunities for use of

methyl soyate as a solvent.

125

References

1.

10.

11.

12.

13.

Vink, E.T.H., et al., Applications of Life Cycle Assessment to Nature Worksm
Polyactide (PLA) Production. Polymer Degradation and Stability, 2003. 80(3): p.
403-419.

Chrispeels, M.J. and DE. Sadava, Chapter 19: Plants as Chemical and
Pharmaceutical Factories, in Plants, Genes and Crop Biotechnology. 2003, Jones
& Bartlett Publishers, Inc.

Hill, K., Fats and Oils as Oleochemical Raw Materials. Pure & Applied
Chemistry, 2000. 72(7): p. 1255-1264.

Gunstone, F.D. and PB. Padley, eds. Lipid Technologies and Applications. 1997,
Marcel Dekker, Inc.: New York.

Diesel, R., The Diesel Oil-Engine. Engineering, 1912. 93: p. 395-406.

Nitske, W.R. and C.M. Wilson, Rudolf Diesel, Pioneer of the Age of Power. 1965,
Norman: University of Oklahoma Press.

Werner, K., The Technical, Energy and Environmental Properties of BioDiesel.
1993, Korbitz Consulting: Vienna, Austria.

Ziejewski, M. and KR. Kaufman, Laboratory Endurance Test of a Sunﬂower Oil
Blend in a Diesel Engine. JAOCS, 1983. 60(8): p. 1567-1573.

Pahl, G., Biodiesel: Growing a New Energy Economy. 2005, White River
Junction: Chelsea Green Publishing Company.

Farmer, E.H., H.P. Koch, and DA. Sutton, Course of Autoxidation Reactions in
Polyisoprenes and Allied Compounds. VII. Rearrangement of Double Bonds
During Autoxidation. Journal of the Chemical Society, Abstracts, 1943: p. 541-
547.

Lundberg, W.O., ed. Autoxidation and Anitioxidants. Vol. 1. 1961, Interscience
Publishers: New YOrk. 450.

Stirton, A.J., J. Turer, and R.W. Riemenschneider, Oxygen Absorption of Me
Esters of Fat Acids, and the Eﬂect of Antioxidants. Oil and Soap, 1945. 22: p. 81-
83.

Technical Statement on the Use ofBiodieseI Fuel in Compression Ignition
Engines. 2003, EMA Technical Standard.

126

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

Diesel Fuel Injection Equipment Manufacturers Common Position Statement on
Fatty Acid Methyl Ester Fuels as a Replacementor Extender for Diesel Fuels.
1 998.

Duplessis, L.M., J .B.M. Devilliers, and W.H. Vanderwalt, Stability Studies on
Methyl and Ethyl Fatty-Acid Esters of Sunﬂowerseed Oil. JAOCS, 1985. 62(4): p.
748-752.

Bondioli, P., et al., Storage Stability of Biodiesel. JAOCS, 1995. 72(6): p. 699-
702.

Canakci, M., A. Monyem, and J. Van Gerpen, Accelerated oxidation processes in
biodiesel. Transactions of the Asae, 1999. 42(6): p. 1565-1572.

Mittelbach, M. and S. Gangl, Long storage stability of biodiesel made from
rapeseed and used ﬂying oil. JAOCS, 2001. 78(6): p. 573-577.

Monyem, A., J .H. Van Gerpen, and M. Canakci, The eﬂect of timing and
oxidation on emissions from biodiesel-fueled engines. Transactions of the ASAE,
2001. 44(1): p. 35-42.

Monyem, A. and J.H. Van Gerpen, The effect of biodiesel oxidation on engine
performance and emissions. Biomass & Bioenergy, 2001. 20(4): p. 317-325.

Knothe, G., J. m, and J.V. Gerpen, eds. The Biodiesel Handbook. 2005, AOCS
Press: Champaign.

Graboski, MS. and R.L. McCormick, Combustion of Fat and Vegetable Oil
Derived Fuels in Diesel Engines. Prog. Energy Combust. Sci., 1998. 24: p. 125-
164.

Dunn, R.O. and MO. Bagby, Low-Temperature Properties of T riglyceride-Based
Diesel Fuels - Transesteriﬁed Methyl-Esters and Petroleum Middle
Distillate/Ester Blends. JAOCS, 1995. 72(8): p. 895-904.

Knothe, G. and RC. Dunn, Bioﬁrels Derived from Vegetable Oils and Fats, in
Olechemical Manufacture and Applications, F.D. Gunstone and R.J. Hamilton,
Editors. 2001, CRC Press LLC: Boca Raton.

Dunn, R.O., M.W. Shockley, and MO. Bagby, Improving the Low-Temperature
Properties of Alternative Diesel Fuels: Vegetable Oil-Derived Methyl Esters.
JAOCS, 1996. 73(12): p. 1719-1728.

Lee, 1., LA. Johnson, and E.G. Hammond, Reducing the Crystallization
Temperature of Biodiesel by Winterizing Methyl Soyate. JAOCS, 1996. 73(5): p.
63 1 -63 6.

127

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37.

38.

39.

40.

Lee, 1., L.A. Johnson, and E.G. Hammond, Use of Branched-Chain Esters to
Reduce the Crystallization Temperature of Biodiesel. JAOCS, 1995. 72(10): p.
1155-1160.

Karaosmanoglu, F., et al., Investigation of the Reﬁning Step of Biodiesel
Production. Energy & Fuels, 1996. 10(4): p. 890-895.

Schwab, A.W., M.O. Bagby, and B. Freedman, Preparation and properties of
diesel ﬁrels from vegetable oils. Fuel, 1987. 66(19): p. 1372-1378.

Schober, B.D., Ozonolysis and Reduction in Fine Chemicals Industry. Chimica
Oggi-Chemistry Today, 1995. 13(6): p. 21-24.

Criegee, R. and G. Wenner, Ozonization of 1,2, 3, 4, 5, 6, 7, 8-octahydronaphthalene.
Ann., 1949.564: p. 9-15.

Rakovsky, S. and G. Zaikov, Kinetics and Mechanism of Ozone Reactions with
Organic and Polymeric Compounds in Liquid Phase. 1998, Commack: Nova
Science Publishers, Inc.

Rice, R.G. and A. Netzer, eds. Handbook of Ozone Technology and Applications.
Vol. 1. 1982, Ann Arbor Science Publishers: Ann Arbor.

Razurnovskii, SD. and GE. Zaikov, Ozone and Its Reaction With Organic
Compounds. 1984, Amsterdam: Elsevier Science Publishers B. V.

Marshall, J .A. and A.W. Garofalo, Oxidative Cleavage of Monosubstituted,
Disubstituted, and T risubstituted Oleﬁns to Methyl-Esters through Ozonolysis in
Methanolic Sodium Hydroxide. Journal of Organic Chemistry, 1993. 58(14): p.
3675-3680.

Marshall, J .A., A.W. Garofalo, and RC. Sedrani, The Direct Conversion of
Olefins into Esters through Ozonolysis. Synlett, 1992(8): p. 643-645.

Ma, F. and MA. Hanna, Biodiesel Production: A Review. Bioresource
Technology, 1999. 70: p. 1-15.

Kumar, S., A.K. Gupta, and SN. Naik, Conversion of Non-edible Oil into
Biodiesel. Journal of Scientiﬁc & Industrial Research, 2003. 62: p. 124-132.

Sinha, S. and NC. Misra, Diesel Fuel Alternative ﬁom Vegetable Oils. Chemical
Engineering World, 1997. 32(10): p. 77-80.

Schwab, A.W., et al., Diesel Fuel ﬁom Thermal Decomposition of Soybean Oil.
JAOCS, 1988. 65(11): p. 1781-1786.

128

41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

51.

52.

53.

Nawar, W.W., Thermal Degradation of Lipids: A Review. Journal of Agricultural
and Food Chemistry, 1969. 17(1): p. l8—21.

Dandik, L. and HA. Aksoy. Converting Used Oil to Fuel and Chemical
Feedstock through the Use of a F ractionating Pyrolysis Reactor. in World
Conference on Oilseed and Edible Oils Processing. 1996. Istanbul, Turkey:
AOCS Press.

Sharma, R.K. and N.N. Bakhshi, Catalytic Upgrading of Biomass-Derived Oils to
Transportation Fuels and Chemicals. Canadian Journal of Chemical Engineering,
1991. 69(5): p. 1071-1081.

Katikaneni, S.P.R., J.D. Adjaye, and N.N. Bakhshi, Catalytic Conversion of
Canola Oil to Fuels and Chemicals over Various Cracking Catalysts. Canadian
Journal of Chemical Engineering, 1995. 73(4): p. 484-497.

Katikaneni, S.P.R., J .D. Adjaye, and N.N. Bakhshi, Studies on the Catalytic
Conversion of Canola Oil to Hydrocarbons - Inﬂuence of Hybrid Catalysts and
Steam. Energy & Fuels, 1995. 9(4): p. 599-609.

Chang, CC. and SW. Wan, Chinas Motor Fuels from T ung Oil. Industrial and
Engineering Chemistry, 1947. 39(12): p. 1543-1548.

Alencar, J .W., P.B. Alves, and A.A. Craveiro, Pyrolysis of Tropical Vegetable-
Oils. Journal of Agricultural and Food Chemistry, 1983. 31(6): p. 1268-1270.

Konwer, D., et al., Liquid Fuels from Mesua-Ferrea L Seed Oil. JAOCS, 1989.
66(2): p. 223-226.

Grossley, T.D., T.D. Heyes, and B.J.F. Hudson, The Eﬂect of Heat on Pure
Triglycerides. JAOCS, 1962. 39(9-14).

Niehaus, R.A., et al., Cracked Soybean Oil as 0 Fuel for a Diesel Engine.
Transactions of the ASAE, 1986. 29(3): p. 683-689.

Pioch, D., et al., Bioﬁielsfrom Catalytic Cracking of Tropical Vegetable Oils.
Oleagineux, 1993. 48(6): p. 289-291.

Dandik, L. and HA. Aksoy, Pyrolysis of Used Sunﬂower Oil in the Presence of
Sodium Carbonate by Using Fractionating Pyrolysis Reactor. Fuel Processing
Technology, 1998. 57: p. 81-92.

Dandik, L., H.A. Aksoy, and A. Erdem-Senatalar, Catalytic Conversion of Used

Oil to Hydrocarbon Fuels in a Fractionating Pyrolysis Reactor. Energy & Fuels,
1998. 12: p. 1148-1152.

129

54.

55.

56.

57.

58.

59.

60.

61.

62.

63.

64.

65.

66.

67.

Billaud, F., et al., Production of Hydrocarbons by Pyrolysis of Methyl Esters form
Rapeseed Oil. JAOCS, 1995. 72(10): p. 1149-1154.

Michael, W.R., Alexande.Jc, and NR. Artrnan, Thermal Reactions of Methyl
Linoleate .1. Heating Conditions Isolation Techniques Biological Studies and
Chemical Changes. Lipids, 1966. 1(5): p. 353-357.

Moulton, K.J., et al., Method of Producing Short Chain Methyl Esters. 1963:
United States.

Smith, J.W., B.D. Batts, and TD. Gilbert, Hydrous Pyrolysis of Model
Compounds. Organic Geochemistry, 1989. 14(4): p. 365-373.

Whitmore, F.C., Chemical Engineering & News, 1948. 26: p. 668.

Voge, H.H. and GM. Good, Thermal Cracking of Higher Paraﬂins. JAOCS,
1949. 71(2): p. 593-597.

Shihadeh, A. and S. Hochgreb, Diesel Engine Combustion of Biomass Pyrolysis
Oils. Energy & Fuels, 2000. 14: p. 260-274.

Schlautrnan, N.J., J .L. Schinstock, and M.A. Hanna, Unrefined Expelled Soybean
Oil Performance in a Diesel Engine. Transactions of the ASAE, 1986. 29(1): p.
70-73, 80.

Schlick, M.L., M.A. Hanna, and J.L. Schinstock, Soybean and Sunﬂower Oil
Performance in a Diesel Engine. Transactions of the ASAE, 1988. 31(5): p. 1345-
1349.

Adams, C., eta1., Investigation of Soybean Oil as a Diesel Fuel Extender:
Endurance Tests. JAOCS, 1983. 60(8): p. 1574-1579.

Isigigur, A., et al., Saﬂlower Seed Oil of Turkish Origin as a Diesel Fuel
Alternative. Applied Biochemistry & Biotechnology, 1993. 40: p. 89-105.

Boruff, P., et al. Engine Evaluation of Diesel F uel-Aqueous Ethanol
Microemulsions. in American Society of Agricultural Engineers Winter Meeting.

1980. Chicago, IL: ASAE.

Schwab, A.W. and EH. Pryde, Triglyceride-Methanol Microemulsions. Journal
of Dispersion Science & Technology, 1985. 6(5): p. 563-574.

Goering, C.E., et al., Soyoil-Ethanol Microemulsions as Diesel Fuel. Transactions
of the ASAE, 1983: p. 1602-1607.

130

68.

69.

70.

71.

72.

73.

74.

75.

76.

77.

78.

79.

80.

81.

Goering, CE. and B. Fry, Engine Durability Screening Test of a Diesel Oil/Soy
Oil/Alcohol Microemulsion Fuel. JAOCS, 1984. 61(10): p. 1627-1632.

Masjuki, H., et al., Palm Oil Diesel Emulsion as a Fuel for Diesel Engine:
Performance and Wear Charateristics. Journal for Energy, Heat and Mass
Transfer, 1994. 16: p. 295-304.

Schwab, A.W., et al., T riglyceride/Aqueous Ethanol/1 -Butanol Microemulsions.
Journal of Dispersion Science & Technology, 1983. 4(1): p. 1-17.

Peterson, C.L., Vegetable Oil as a Diesel Fuel: Status and Research Priorities.
Transactions of the ASAE, 1986. 29(5): p. 1413-1422.

Bondioli, P., The preparation of fatty acid esters by means of catalytic reactions.
Topics in Catalysis, 2004. 27(1-4): p. 77-82.

Demirbas, A., Biodiesel Fuels from Vegetable Oils via Catalytic and Non-
catalytic Supercritical Alcohol Transesteriﬁcation and other Methods: A Survey.
Energy Conversion and Management, 2003. 44: p. 2093-2109.

Hoydonckx, H.E., et al., Esterification and transesteriﬁcation of renewable
chemicals. Topics in Catalysis, 2004. 27(1-4): p. 83-96.

Shah, S., S. Sharma, and MN. Gupta, Enzymatic transesteriﬁcation for biodiesel
production. Indian Journal of Biochemistry & Biophysics, 2003. 40(6): p. 392-
399.

Fukuda, H., A. Kondo, and H. Noda, Biodieselﬁrel production by
transesteriﬁcation of oils. Journal of Bioscience and Bioengineering, 2001. 92(5):
p. 405-416.

Schuchardt, U., R. Sercheli, and RM. Vargas, Transesteriﬁcation of Vegetable
Oils: A Review. Journal of the Brazilian Chemical Society, 1998. 9(3): p. 199-
210.

Gutsche, B., Technology of methyl ester production and its application to
biofuels. Fett-Lipid, 1997. 99(12): p. 418-427.

Haas, M.J., G.J. Piazza, and T.A. F oglia, Enzymatic Approaches to the
Production of Biodiesel Fuels, in Lipid Biotechnology, T.M. Kuo and H.W.
Gardner, Editors. 2002, Marcel Dekker: New York.

Freedman, 8., RD. Butterﬁeld, and EH. Pryde, Transesteriﬂcation Kinetics of
Soybean Oil. JAOCS, 1986. 63(10): p. 1375-1380.

Eckey, E.W., Esterification and Interesteriﬁcation. JAOCS, 1956. 33: p. 575-579.

131

82.

83.

84.

85.

86.

87.

88.

89.

90.

91.

92.

93.

94.

95.

Sridhara.R and I.M. Mathai, Transesteriﬁcation Reactions. Journal of Scientiﬁc &
Industrial Research, 1974. 33(4): p. 178-187.

Mittelbach, M. and B. Trathnigg, Kinetics of Alkaline Catalyzed Methanolysis of
Sunﬂower Oil. F ett Wissenschaﬁ Technologie-Fat Science Technology, 1990.
92(4): p. 145-148.

Noureddini, H. and D. Zhu, Kinetics of transesteriﬁcation of soybean oil. JAOCS,
1997. 74(11): p. 1457-1463.

Wright, H.J., et al., Report on Ester Interchange, in Oil & Soap. 1944. p. 145-148.

Freedman, B., E.H. Pryde, and TL. Mounts, Variables Aﬂecting the Yields of
Fatty Esters from Transesteriﬁed Vegetable-Oils. JAOCS, 1984. 61(10): p. 1638-
1643.

F euge, RC. and A.T. Gros, Modification of Vegetable Oils. VII. Alkali Catalyze
Interesteriﬁcation of Peanut Oil with Ethanol. JAOCS, 1949. 26: p. 97-102.

Bradshaw, GB. and WC. Meuly, Soap. 1944, 2,360,844: United States.

Ma, F., L.D. Clements, and M.A. Hanna, The ejfects of catalyst, ﬁee fatty acids,
and water on transesteriﬁcation of beef tallow. Transactions of the Asae, 1998.
41(5): p. 1261-1264.

Encinar, J .M., et al., Biodieselﬁtelsﬁ'om vegetable oils: T ransesteriﬁcation of
C ynara cardunculus L. oils with ethanol. Energy & Fuels, 2002. 16(2): p. 443-
450.

Tanaka, Y., A. Okabe, and S. Ando, Method for the Preparation of Lower Alkyl
Ester or Fatty Acid. 1981, 4,303,590: US.

Ulf Schuchardt, RS. and RM. Vargas, Transesteriﬁcation of Vegetable Oils: A
Review. Journal of the Brazilian Chemical Society, 1998. 9(3): p. 199-210.

Forrno, M.W., Ester Reactions of Fatty Materials. JAOCS, 1954. 31: p. 548-559.
Ikwuagwu, O.E., I.C. Ononogbu, and O.U. Njoku, Production of Biodiesel Using
Rubber [Hevea brasiliensis (Kunth. Muell.)] Seed Oil. Industrial Crops and
Products, 2000. 12(1): p. 57-62.

Kusy, P.F. Tranesterification of Vegetable Oils for Fuels. in International

Conference on Plant and Vegetable Oils as Fuels. 1982. St. Joseph, MI:
American Society of Agricultural Engineers.

132

96.

97.

98.

99.

100.

101.

102.

103.

104.

105.

106.

107.

108.

Boocock, D.G.B., et al., Fast formation of high-purity methyl esters ﬁom
vegetable oils. JAOCS, 1998. 75(9): p. 1167-1172.

Boocock, D.G.B., et al., Fast one-phase oil-rich processes for the preparation of
vegetable oil methyl esters. Biomass & Bioenergy, 1996. 11(1): p. 43-50.

Clark, S.J., et al., Methyl and Ethyl Soybean Esters as Renewable Fuels for
Diesel-Engines. JAOCS, 1984. 61(10): p. 1632-1638.

Sims, R.E.H., Tallow Esters as an Alternative Diesel Fuel. Transactions of the
ASAE, 1985. 28(3): p. 716-721.

Skoog, DA. and J .J . Leary, Principles of Instrumental Analysis. 4th ed. 1992,
Fort Worth: Saunders College Publishing.

Dallas, G., et al., A New Technology to Improve DSC Performance. American
Laboratory, 2001. 33(16): p. 26-29.

Cebula, DJ. and K.W. Smith, Diﬂerential Scanning Calorimetry of Confectionery

Fats. Pure Triglycerides: Eﬂects of Cooling and Heating Rate Variation.
JAOCS, 1991. 68(8): p. 591-595.

ASTM, Method D 25 00: Standard Test Method for Cloud Point of Petroleum
Products in Annual Book of AS TM Standards. Section Five: Petroleum Products,
Lubricants, and Fossil Fuels, N.C. Baldini, et al., Editors. 2002, ASTM
International: West Conshohocken.

ASTM, Method D 97: Standard Test Method for Pour Point Petroleum Products,
in Annual Book of ASTM Standards. Section Five: Petroleum Products,
Lubricants, and Fossil Fuels, N.C. Baldini, et al., Editors. 2002, ASTM
International: West Conshohocken.

ASTM, Method D 63 71: Standard Test Method for Cold Filter Plugging Point of
Diesel and Heating Fuels, in Annual Book of AS T M Standards. Section Five:
Petroleum Products, Lubricants, and Fossil Fuels, N.C. Baldini, et al., Editors.
2002, ASTM International: West Conshohocken.

Steffe, J .F., Rheological Methods in Food Process Engineering. 2nd ed. 1996,
East Lansing: Freeman Press.

Karyakin, A.V., V.A. Nikitin, and K.I. Ivanov, Inﬁakrasnye Spektry Perekisei.
Zhurnal F izicheskoi Khimii, 1953. 27(12): p. 1856-1866.

Criegee, R., A. Kerckow, and H. Zinke, Der Bildungsbereich Monomerer
Ozonide. Chemische Berichte-Recueil, 1955. 88(12): p. 1878-1888.

133

109.

110.

111.

112.

113.

114.

115.

116.

117.

118.

119.

120.

121.

Briner, E. and E. Dallwigk, Recherches Sur Les Spectres Dabsorption Ir Des
Ozonides.11. Modifications Dattributions Et Nouvelles Attributions Des Bandes
Dabsorption Des Produits Dozonation. Helvetica Chimica Acta, 1956. 39(5): p.
1446-1450.

Dallwigk, E. and E. Briner, Recherches Sur Les Spectres Dabsorption Ir Des
Ozonides. 12. Modifications Dattributions Et Nouvelles Attributions Des Bandes
Dabsorption Des Produits Dozonation - Presentation De Spectres Et
Commentaires. Helvetica Chimica Acta, 1956. 39(6): p. 1826-1833.

Briner, E. and E. Dallwigk, Spectres Dabsorption Infrarouge Des Produits
Dozonation De Corps Organiques Non Satures. Comptes Rendus Hebdomadaires
Des Seances De L Academic Des Sciences, 1956. 243(7): p. 630-634.

Garvin, D. and C. Schubert, The Vapor Phase Infrared Spectra of the Ozonides of
Ethylene, Propylene and Isobutylene. Journal of Physical Chemistry, 1956. 60(6):
p. 807-808.

Razumovskii, S.D.B., L. V.; Gil'chenok, N. D.; Oranskaya, O. M.; Yur'ev, Yu. N.;
Tsyskovskii, V. K. , Ozonation of I-hezene and Properties of Ozonides. Zhurnal
Organicheskoi Khimii 1966. 2(11): p. 1942-1946.

Wu, M.D., et al., Separation and Spectral Data of the 6 Isomeric Ozonidesfrom
Methyl Oleate. Lipids, 1992. 27(2): p. 129-135.

Bellamy, L.J., The Infra-Red Spectra of Complex Molecules. 1958, New York:
John Wiley & Sons, Inc.

Diaz, M.F., et al., I H NMR Study of Methyl Linoleate Ozonation. Ozone Science
& Engineering, 2002. 25: p. 121-126.

Nestor U. Soriano, J ., V.P. Migo, and M. Matsumura, Ozonation of Sunﬂower
Oil: Spectroscopic Monitoring of the Degree of Unsaturation. JAOCS, 2003.
80(10): p. 997-1001.

Diaz, M.F., et al., Spectroscopic Characterization of Ozonated Sunﬂower Oil.
Ozone-Science & Engineering, 2005. 27(3): p. 247-253.

Canakci, M. and J .V. Gerpen, A Pilot Plant to Produce Biodieselﬁom High Free
Fatty Acid Feedstocks. Transactions of the ASAE, 2003. 46(4): p. 945-954.

F ogler, H.S., Elements of Chemical Reaction Engineering. 3rd ed. 1999, Upper
Saddle River: Prentice Hall PTR.

Ledea, O., et al., Volatile Components of Ozonized Sunﬂower Oil "OLEOZONW ".
Ozone-Science & Engineering, 2001. 23(2): p. 121-126.

134

122.

123.

124.

125.

126.

127.

128.

129.

130.

131.

132.

133.

Hancock, R.A., N.J. Leeves, and P.F. Nicks, Studies in Autoxidation. Part1. The
Volatile By-Products Resulting ﬁom the Autoxidation of Unsaturated Fatty Acid
Methyl Esters. Progress in Organic Coatings, 1989. 17(3): p. 321-336.

Frankel, E.N., WE. Neff, and E. Selke, Analysis of Auto-Oxidized Fats by Gas
C hromatography-Mass Spectrometry: VII. Volatile Thermal Decomposition
Products of Pure Hydroperoxides from Auto-Oxidized and Photosensitized
Oxidized Methyl Oleate, Linoleate and Linolenate. Lipids, 1981. 16(5): p. 279-
285.

Huber, H., Oxidation of Petroleum Distillates to Obtain Higher Crystallized
Ethers, and Higher Liquid Ethers, in United States Patent Office. 1962, Henri
Huber: United States.

Bartok, W. and CE. Heath, Process for Partial Oxidation of Ethane to Produce
Formaldehyde, in United States Patent Oﬁ‘ice. 1962, Esso Research and
Engineering Company: United States.

Shotts, A.C., Oxidation of Unsaturated Hydrocarbons, in United States Patent
Office. 1963, Cities Serive Research and Development Company: United States.

Lide, D.R., ed. CRC Handbook of Chemistry and Physics. 82"d ed. 2001, CRC
Press: New York.

Dunn, R.O., Thermal Analysis of AlternativeDiesel Fuels ﬁom Vegetable Oils.
JAOCS, 1999. 76(1): p. 109-115.

Walter M. Budde, J ., General Physical and Chemical Properties of Fatty Acids,
in Fatty Acids and Their Industrial Applications, E.S. Pattison, Editor. 1968,
Marcel Dekker, Inc.: New York.

Lee, I., L.A. Johnson, and E.G. Hammond, Reducing the Crystallization
Temperature of Biodiesel by Winterizing Methyl Soyate. JAOCS, 1996. 73(5): p.
631-636.

Wu, W.-H., et al., Low-Temperature Property and Engine Performance
Evaluation of Ethyl and Isopropyl Esters of Tallow and Grease. J AOCS, 1998.
75(9): p. 1173-1178.

Goebel, G.G., et al. 1957, Emery Industries: U. S.

Peters, R.A., Fatty Alcohol Production and Use. INFORM, 1996. 7: p. 502-504.

135

134.

135.

136.

137.

Mushrush, G., et al., An environmentally benign soybean derived ﬁre] as a
blending stock or replacement for home heating oil. Journal of Environmental
Science and Health Part a-Toxic/Hazardous Substances & Environmental
Engineering, 2001. 36(5): p. 613-622.

Miller, NJ. and SM. Mudge, The eﬂect of biodiesel on the rate of removal and
weathering characteristics of crude oil within artificial sand columns. Spill
Science & Technology Bulletin, 1997. 4(1): p. 17-33.

Mudge, SM. and G. Pereira, Stimulating the biodegradation of crude oil with
biodiesel preliminary results. Spill Science & Technology Bulletin, 1999. 5(5-6):
p. 353-355.

Pereira, MG. and SM. Mudge, Cleaning oiled shores: laboratory experiments

testing the potential use of vegetable oil biodiesels. Chemosphere, 2004. 54(3): p.
297-304.

136

IIIIIIIIIIIIIIIIIIIIIIIIIIIIII

11111111llllllIllililllllllllIllilllllllllllllll

293 273