Qo wht ow
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
6/01 c:/CIRC/DateQue.p65-p. 15
THE
DEVELOPMENT OF 4 COMMER CIAL
PROCESS
FOR THE MANUFACTURE oF
DIMETHYLANILINE.
A THESIS
Submitted to the Faculty of the
MICHIGAN AGRICULTURAL COLLEGE
BY
RAYMOND LEROY BAX?ER
Candidate for the Degree
Of Chemical Engineer.
1920.
wN
reer
CONTENTS
Chapter
I Introduction.
II Dimethylaniline: Its importance and use.
Iftl Literature.
IV Experimental Work.
V Design of plant: Operation, and costs.
93879
CHAPTER I.
INTRODUCTION.
Prior to the Great War the production of
dyes in the United States was negligible. Of the
total consumption only about one fifth was produced
in this country, or about 3,000 short tons, and
practically all of the intermediates or basis of
these colors were imported from Germany.
In the year 1914 about seven companies were
engaged in producing dyes employing about 600 men,
and having a total capital of $3,000 (000. The
quanity produced was as Said before, about 6,000,000
pounds with a value of $3,500,000.
In 1918 the United States produced approximately
76,802,959 pounds of different dyes with a total
Valuation of $63,815,746.
Nowe
CHAPTER II.
DIMETHYLANALINE: ITS IMPORTANCE AND USE.
From the ten substances or “crudes" as they
are commonly designated, obtained from coal tar
suitable for making dyes, three hundred intermediates
are manufactured. These three hundred intermediates
from the bases of about nine hundred dyes of commercial
importance at the present time.
The intermediates are divided into about ten
different classes according to the characteristic
groups which they contain. Dimethyl-aniline is a
member of the Secondary Amines and their derivatives
group. It is superceded only by déphenylamine in
quantity used and which amounts to 4,263,458 pounds
with a value of $2,412,820.
At the present time the demand far exceeds
the amount produced.
It finds its main use in the manufacture of
two very important dye stuffs, namely, Malachete
Green and Mekhyl Violet. The quanity of these dyes
used amounts to 290,416 pounds with e valuation of
$1,626,466 for Malachete Green and 632,196 pounds
with a valuation of $1,756,775 for Methyl Violet.
Prom the above figures it can be readily
seen that this compound is of considerable commercial
importance. To develop a process for its manufacture
commercially was a problem thought worthy of under-
taking.
CHAPTER III.
LITERATURE.
The first steps in the work of developing
a commercial process for the manufacture of dimethyl-
aniline was to examine the literature, and to
discover if possible what work had been done on the
manufacture of this intermediate.
A thoro examination revealed that while it
was being manufactured in Germany in considerable
quantity very little had been written regarding the
type of apparatus used and the control of the process.
It was found that there were four processes
of commercial value which are as follows:
ANILINE HYDROCHLORIDE PROCESS
A mixture of aniline seventy-five parts,
aniline hydrochloride twenty-five parts, and methyl
alcohol (free from acetone) seventy-five parts is
heated in a cast iron auto clave at 230° to 270°.
METHYL CHLORIDE PROCESS. |
Aniline (50 kilos) is well agitated in an : |
|
auto-clave with milk of lime made from 40 kilos of
5.
quick line and 75 litres of water. The whole is
heated to 100° C. and methyl chloride pumped in at
5-6 atmospheres pressure. About 62 kilos of methyl
chloride are required and the time taken about three
hours. The dimethyl aniline is then distilled with
stean.
THE IODINE PROCESS.
This process consists in heating aniline with
methyl alcohol and iodine at 230° C for seven hours.
Distilling off the dimethyl aniline with stean.
THE SULPHURIC ACID PROCESS.
Bighty kilograms of aniline, seventy-eight
kilograms of methyl alcohol and eight kilograms of
sulphuric acid 66° Be, ate heated together in an
autoclave at 230° to 235°. The pressure rises to
twenty-eight to thirty-two atmospheres. This pressure
remains constant for three hours after whioh it falls
off as the reaction slows up. The proémct is then
neutralised with caustic soda and the dimethyl aniline
distilled with steam. |
From these four processes the "Sulphuric Acid
Process" was chosen as having the likeliest commroial
possibilities.
The aniline hydrochloride process was
rejected because of the cost of aniline hydro-
chloride and because of the extremely high wear
and tear On apparatus caused by the volatile acid.
The Methyl Chloride Procese was considered
unsuitable because of the excessive cost of Methyl
Chloride.
The Iodine Process was also dropped because
of the price of Iodine.
There is one other process which has not been
meationed before but which seems to have commercial
possibilities. This is the treatment of aniline with
dimethyl sulphate. At the present time nothing has
been done with it, but it is a process worthy of
looking carefully into.
CHAPTER IV
EXPERIMENTAL WORK.
It is thought that the reactions in the
"Sulphuric Acid Process" are as follows:
&
CHZ0H + Hp80, > (CHg), 80, + 8H,0
In order to carry on the work in the
laboratory it immediately became necessary to
develop some sort of a simple inexpensive piece of |
apparatus capable of standing the tremendous pressure
involved in the reaction.
A bomb made of a piece of two inch pipe six
inches long and capped at both ends which was to be
heated in an oil bath was first concieved. This bomb
held a charge of eighty grams of aniline, seventy-
eight grams of methyl alcohol, and eight gran of
sulphuric acid 66° Be. This was to give a yield of
ninety six grams of di-methyl aniline.
The bomb was heated in an oil bath at 280° to
BS0° for five hours. It became apparent during this
first run that it was going to be difficult to keep
the bomb tight under the temperature and excessive
pressure conditions, and it may be said right here
that this difficulty was encountered thruout all of
the laboratory work and the semi manufacturing scale
as well. It proved to be the hardest difficulty to surmount
and one which is very important as the success of the
process depends upon there being no leaks of pressure
Since during the time of a run even the very slightest
leak will cause a loss of aloohol in the form of vapor
which will prevent complete oonversion and the produot
will be contaminated with the mono methyl compound.
The yield of di-methyl aniline from this
first run was only fifty two grams and of very poor
quality.
sulphuric acid 66° Be. heated at 230° C for twelve
hours. and s are closed, the mixture
collecting separates the water flowing off at s)
and the dimethyl-aniline at Pp into the sponge
filter, Plate VIII.
The sponge filter consists of a tank which
is partly filled with a bag of sponges. The sponges
take up what little water is left in the dimethyl
aniline and it is ready for shipping.
After steam distillation dimethyl-aniline
should not come in contact with copper, bronze or
brass as it is discolored by these metals. This
same will occur in glass bottles when exposed to
Ss
light and especially with simultaneous addition of
air.
Cast or sheet iron drums are to be used as
containors when shipping.
21
DETAILS OF OPERATION.
Work is started at six in the morning. The
autoclaves are charged from the masuring tanks wi th
80 kilograms of aniline, 78 kilograms of methyl
alcohol and 8 kilograms of sulphurié acid in each.
It is thot desirable to prepare the aloohol and
sulphuric acid a head of time as this tends to speed
up the reaction. Half of the aniline is run in and
then the alcohol and sulphuric acid and then the
rest of the aniline. It is figured that the loading
ought to be completed by 10 o'clock at whioh time
heating is begun and the temperature held at 230° to
235° C. as shown by a thermometer placed in the metal
bath. At about 2 o'clock in the afternoon the maximum
pressure ought to be reached. This pressure remains
constant for about three hours and recedes slightly
there after. At 11 o'clock at night the heating is
completed and the autoclaves allowed to cool until
the next morning.
In the moming the blowing off is started:
the blow off valves in the autoclaves are slowly opened,
these are connected to a system of pipes which oonvey
the issuing gases and steam to a condenser in which
the methyl alcohol condenses. The gases which pases
thru the oondenser consisting mainly of methyl ether
22
are passed thru a water scrubber before being
released into the air. This sorubber will alse
keep back any methyl alcohol that passes thru the
condenser.
After all the pressure is released, the
blowing off of the product into the steam still is
commenced. This is accomplished by means of con-
pressed air.
A little water and sufficient Caustic soda
to neutralize the excess acid are placed in the still.
As 800n as the dimethyl-aniline is all in,a little
steam is turned into the inside to mix the contents,
then the steam is turned into the jacket. Water and
methyl alcohol distill off first and are condensed.
After most of this alcohol is out, steam is turned
into the inside of the still. ‘fhe steam carries out
the dimethyl-aniline and also a little alcohol which
remains. This passes into the first condenser where
the steam and dimethyl-aniline are condensed and
returned to the still; the methyl alcohol passes on to
the second condenser where it is cond ensed and collected.
The distillation is carried on slowly until drops of
dimethyl-aniline separate rapidly from the mixture in
the still. The vapours are now conducted direotly
into the large condenser. The condensate which is a
mixture of water and dimethyl-aniline is then run
uy .
a
25
into the separating tank where the dimethyl-aniline
is drawn off and the water flows away. From the
separating tank the dimethyl-aniline is run into a
sponge filter which removes all of the water. The
dimethyl-aniline is now placed in oontainers for
shipping.
There is little more to say in regard to
details of operation. Three ma@m on each shift ought
to be sufficient to run the entire plant.
STEAM REQUIREMENTS.
During the maximum distillation period the
condensate consists of 1 part dimethyl-aniline and
6 parts water added as steam. However, before and
after this period mre steam is required, further
the jacket of the still is steam heated and steam is
used for the compressing of air. Therefore, six
fold weight is not sufficient and it is figured that
15 parts of steam to 1 part of dimethyl-aniline will
be required. At the present time it is impossible
to figure the cost of this as the price of coal is go
variable.
TESTING OF DIMETHYL-ANILINE.
For the determination of mono-methyl-aniline
YY
24
the acetic anhydride test is used. acetic anhydride
added to pure dimethyl-aniline causes a lowering of
the temperature of almost 1 degree. In the best
commercial grades about 1/2 degree. If the mono-
methyl-aniline content is not too high 1° increase
in temperature corresponds to about 1/2% of mono-
methyl-aniline (exact .815° for 1% mono methyl-
aniline acoording to the Chemiker Zeitung 1889 S387).
The specifications for de-nethyl-aniline at
the present time are that it mst have a boiling
point within 4° of its true boiling point, which
is 192° C. allowing a variation of 2°- or 2°+ and
mest not contain mre than 1/2% of mono-methyl-
aniline, this last is very important.
The mono-methyl aniline test is carried out
as follows 10 c.c.of dimethyl-aniline are pipetted
into a test tube and 3 c.a. of acetic anhydride into
another. as he
A _
= i Millions ~
'
IGAN S
HN
3 1293 02244 8132
MICHIGAN STATE LIBRARIES
Whi | ih) i
| | | | iI | |
AAA A
3 1293 02244 8132
™“
“~~
= a La ‘zi ie
; ; = T
le =
&
3 7 ~ — —
7 _
a slg — J
» ie = =
iF , ‘ 7 a
vue i \ ns
of ) - ay 2
a 4
———— = Sieele
~—+
STATE LIB
MICHIGAN § RARIES
aT HAY \I| |
Hil A
| | Wal | |
AN AH NT | |
3 1293 02244 8132
= a
ng
—— — patie c = ~ ;
a
—
7 t ‘
te a
———.
ee — mpage
a hs -
a ee oan =
- =
a ad ’ \ q
MICHIGAN STATE LIBRARIES
\ | Mi
| | |
WILMA AMAA ATA A A
| | IIH II HI
3 1293 02244 8132
I >. : = ~
Pa
ie “ — >.
SERRE ERE REE ESE
RBEREEEEEEE =
) >a Né ne
im | ape Load
ee
Wi y ah t
ck
MICHIGAN STATE |
WAIN A
3 1293 02244 8