LIGNIN	
  DEPOLYMERIZATION	
  AND	
  UPGRADING	
  VIA	
  FAST	
  PYROLYSIS	
  AND	
  
ELECTROCATALYSIS	
  FOR	
  THE	
  PRODUCTION	
  OF	
  LIQUID	
  FUELS	
  AND	
  VALUE-­‐ADDED	
  
PRODUCTS	
  
By	
  
Mahlet	
  Garedew	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
A	
  THESIS	
  
Submitted	
  to	
  	
  
Michigan	
  State	
  University	
  	
  
in	
  partial	
  fulfillment	
  of	
  the	
  requirements	
  	
  
for	
  the	
  degree	
  of	
  	
  
Biosystems	
  and	
  Agricultural	
  Engineering	
  –	
  Master	
  of	
  Science	
  	
  
2014	
  	
  

ABSTRACT	
  	
  
LIGNIN	
  DEPOLYMERIZATION	
  AND	
  UPGRADING	
  VIA	
  FAST	
  PYROLYSIS	
  AND	
  
ELECTROCATALYSIS	
  FOR	
  THE	
  PRODUCTION	
  OF	
  LIQUID	
  FUELS	
  AND	
  VALUE-­‐ADDED	
  
PRODUCTS	
  
	
  
By	
  
Mahlet	
  Garedew	
  
The	
   production	
   of	
   liquid	
   hydrocarbon	
   fuels	
   from	
   biomass	
   is	
   needed	
   to	
   replace	
   fossil	
  
fuels,	
   which	
   are	
   decreasing	
   in	
   supply	
   at	
   an	
   unsustainable	
   rate.	
   	
   Renewable	
   fuels	
   also	
  
address	
   the	
   rising	
   levels	
   of	
   greenhouse	
   gases,	
   an	
   issue	
   for	
   which	
   the	
   Intergovernmental	
  
Panel	
   on	
   Climate	
   Change	
   implicated	
   humanity	
   in	
   2013.	
   	
   In	
   response,	
   the	
   Energy	
  
Independence	
   and	
   Security	
   Act	
   (EISA)	
   mandates	
   the	
   production	
   of	
   21	
   billion	
   gallons	
   of	
  
advanced	
  biofuels	
  by	
  2022.	
  	
  Biomass	
  fast	
  pyrolysis	
  (BFP)	
  uses	
  heat	
  (400-­‐600	
  °C)	
  without	
  
oxygen	
  to	
  convert	
  biomass	
  to	
  liquids	
  fuel	
  precursors	
  offering	
  an	
  alternative	
  to	
  fossil	
  fuels	
  
and	
  a	
  means	
  to	
  meet	
  the	
  EISA	
  mandate.	
  The	
  major	
  product,	
  bio-­‐oil,	
  can	
  be	
  further	
  upgraded	
  
to	
  liquid	
  hydrocarbon	
  fuels,	
  while	
  biochar	
  can	
  serve	
  as	
  a	
  solid	
  fuel	
  or	
  soil	
  amendment.	
  	
  The	
  
combustible	
   gas	
   co-­‐product	
   is	
   typically	
   burned	
   for	
   process	
   heat.	
   Though	
   the	
   most	
   valuable	
  
of	
  the	
  pyrolysis	
  products,	
  the	
  liquid	
   bio-­‐oil	
  is	
  highly	
  oxygenated,	
  corrosive,	
  low	
  in	
  energy	
  
content	
   and	
   unstable	
   during	
   storage.	
   	
   As	
   a	
   means	
   of	
   improving	
   bio-­‐oil	
   properties,	
  
electrocatalytic	
   hydrogenation	
   (ECH)	
   is	
   employed	
   to	
   reduce	
   and	
   deoxygenate	
   reactive	
  
compounds.	
   This	
   work	
   specifically	
   focuses	
   on	
   lignin	
   as	
   a	
   feed	
   material	
   for	
   BFP.	
   As	
   lignin	
  
comprises	
  up	
  to	
  30%	
  of	
  the	
  mass	
  and	
  40%	
  of	
  the	
  energy	
  stored	
  in	
  biomass,	
  it	
  offers	
  great	
  
potential	
   for	
   the	
   production	
   of	
   liquid	
   fuels	
   and	
   value-­‐added	
   products	
   by	
   utilizing	
   fast	
  
pyrolysis	
  as	
  a	
  conversion	
  method	
  coupled	
  with	
  electrocatalysis	
  as	
  an	
  upgrading	
  method.	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
Dedicated	
  to	
  my	
  husband	
  Nicholas	
  James	
  Ballard.	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

iii	
  
	
  

	
  
ACKNOWLEDGEMENTS	
  
	
  
I	
  would	
  like	
  to	
  take	
  this	
  opportunity	
  to	
  express	
  my	
  gratitude	
  to	
  everyone	
  who	
  has	
  
provided	
  support	
  throughout	
  my	
  MS	
  degree.	
  I	
  would	
  like	
  to	
  express	
  my	
  sincere	
  gratitude	
  to	
  
my	
  advisor	
  Dr.	
  Chris	
  Saffron,	
  for	
  his	
  guidance	
  and	
  strong	
  support	
  throughout	
  my	
  MS	
  degree	
  
work	
  and	
  for	
  his	
  continued	
  support	
  in	
  my	
  future	
  pursuit	
  and	
  research	
  work.	
  I	
  have	
  gained	
  a	
  
great	
  deal	
  of	
  knowledge	
  through	
  his	
  guidance	
  in	
  this	
  field.	
  I	
  would	
  like	
  to	
  thank	
  Dr.	
  James	
  
Jackson	
  for	
  his	
  continuous	
  guidance,	
  support	
  and	
  his	
  immense	
  contribution	
  to	
  my	
  research	
  
work.	
   	
   I	
   would	
   also	
   like	
   to	
   thank	
   Dr.	
   David	
   Hodge	
   for	
   his	
   guidance	
   as	
   part	
   of	
   my	
   MS	
  
committee	
   member.	
   Special	
   thanks	
   to	
   Barb	
   DeLong	
   for	
   all	
   her	
   help	
   answering	
   my	
  
department-­‐related	
  questions	
  no	
  matter	
  how	
  trivial.	
  
I	
  would	
  like	
  to	
  give	
  a	
  special	
   thanks	
   to	
   my	
   research	
   group	
   members	
   and	
   colleagues,	
  
Dr.	
  Zhenglong	
  Li,	
  Dr.	
  Shantanu	
  Kelkar,	
  Kristen	
  Henn,	
  Chai	
  Li,	
  Rachael	
  Sak,	
  Nichole	
  Ericson,	
  
Stephen	
  Willson,	
  Dr.	
  Chun	
  Ho	
  Lam,	
  Souful	
  Bhatia,	
  Pengchao	
  Hao,	
  Tayeb	
  Kakeshpour,	
  Greg	
  
Spahlinger,	
   Darya	
   Howell,	
   Fatmata	
   Jalloh,	
   Dr.	
   Mikhail	
   Redko,	
   Andrew	
   Henika,	
   for	
   providing	
  
support	
  and	
  help	
  throughout	
  my	
  stay	
  with	
  the	
  Saffron	
  and	
  Jackson	
  research	
  groups.	
  	
  	
  
I	
   would	
   like	
   to	
   thank	
   my	
   friends	
   and	
   family,	
   Melissa	
   Rojas-­‐Downing,	
   Georgina	
  
Sanchez,	
   Yamile	
   Mennah-­‐Govela,	
   Anne	
   Von	
   Petersdorff-­‐Campen,	
   Meron	
   Garedew,	
   Menna	
  
Garedew	
  for	
  all	
  their	
  personal	
  support,	
  encouragement	
  and	
  love.	
  	
  
Last	
   but	
   not	
   least,	
   I	
   would	
   love	
   to	
   give	
   my	
   heartfelt	
   thanks	
   and	
   gratitude	
   to	
   my	
  
husband,	
  Nick	
  Ballard	
  for	
  being	
  my	
  biggest	
  cheerleader	
  and	
  for	
  the	
  daily	
  encouragement,	
  
love	
   and	
   support	
   that	
   he	
   provides	
   for	
   me.	
   I	
   would	
   not	
   be	
   able	
   to	
   accomplish	
   my	
   goals	
  
without	
  his	
  continuous	
  support.	
  I	
  am	
  grateful	
  to	
  have	
  such	
  a	
  wonderful	
  partner.	
  	
  	
  

iv	
  
	
  

	
  
TABLE	
  OF	
  CONTENTS	
  
	
  
LIST	
  OF	
  TABLES .................................................................................................................................. vii	
  
LIST	
  OF	
  FIGURES................................................................................................................................viii	
  
Chapter	
  1	
  :	
  Introduction	
  and	
  Background................................................................................... 1	
  
Introduction........................................................................................................................................................... 1	
  
Research	
  Objectives ........................................................................................................................................... 4	
  
Energy	
  Crisis	
  and	
  Environmental	
  Impact ................................................................................................. 4	
  
Fossil	
  Fuel	
  Use.................................................................................................................................................. 4	
  
Environmental	
  Impact	
  of	
  Climate	
  Change ........................................................................................... 5	
  
Social	
  Impacts	
  of	
  Climate	
  Change............................................................................................................ 6	
  
Biomass	
  Components ........................................................................................................................................ 7	
  
Lignin:	
  Structure .................................................................................................................................................. 8	
  
Lignin:	
  Isolation	
  Processes........................................................................................................................... 12	
  
Fast	
  pyrolysis	
  as	
  a	
  Depolymerization	
  Process..................................................................................... 13	
  
Characteristics	
  of	
  Bio-­‐oil ............................................................................................................................... 15	
  
Bio-­‐oil	
  Upgrading	
  using	
  Electrocatalytic	
  Hydrogenation ............................................................... 17	
  
Conclusion ........................................................................................................................................................... 22	
  
REFERENCES...................................................................................................................................................... 24	
  
Chapter	
  2	
  :	
  Electrocatalytic	
  Hydrogenation	
  and	
  Deoxygenation	
  of	
  Lignin	
  Model	
  
Compounds	
  using	
  Ruthenium	
  Supported	
  on	
  Activated	
  Carbon	
  Cloth .............................32	
  
Abstract................................................................................................................................................................. 32	
  
Introduction........................................................................................................................................................ 32	
  
Experimental	
  Methods................................................................................................................................... 36	
  
Model	
  Compounds ...................................................................................................................................... 36	
  
Catalyst	
  Preparation................................................................................................................................... 37	
  
Catalyst	
  Characterization......................................................................................................................... 37	
  
Electrocatalytic	
  Hydrogenation	
  (ECH)	
  Setup.................................................................................. 38	
  
Catalyst	
  Deactivation	
  Studies................................................................................................................. 40	
  
Sample	
  Analysis............................................................................................................................................ 40	
  
Calculations.................................................................................................................................................... 40	
  
Results	
  and	
  Discussion................................................................................................................................... 41	
  
Catalyst	
  Characterization	
  (ICP	
  and	
  SEM).......................................................................................... 41	
  
Model	
  Compound	
  Studies:	
  Methoxyphenols	
  with	
  Different	
  Methoxy	
  Group	
  Positions 43	
  
Model	
  Compound	
  Studies:	
  4-­‐O-­‐5	
  Type	
  Linkage	
  (4-­‐phenoxyphenol).................................... 50	
  
Electrolyte	
  Effect.......................................................................................................................................... 51	
  
Current	
  Density	
  and	
  Substrate	
  Concentration................................................................................ 53	
  
Model	
  Compound	
  Studies:	
  β-­‐O-­‐4	
  type	
  Linkage	
  Dimers .............................................................. 54	
  
Catalyst	
  Deactivation ................................................................................................................................. 55	
  
Conclusion ........................................................................................................................................................... 58	
  
REFERENCES...................................................................................................................................................... 60	
  

v	
  
	
  

	
  
Chapter	
  3	
  :	
  Characterization	
  of	
  Extractive	
  Ammonia	
  Process	
  Lignin	
  Fractions...........64	
  
Abstract................................................................................................................................................................. 64	
  
Introduction........................................................................................................................................................ 64	
  
Experimental	
  Methods................................................................................................................................... 68	
  
EAP	
  Lignin	
  Extraction	
  Method............................................................................................................... 68	
  
Higher	
  Heating	
  Value	
  (Bomb	
  Calorimetry)...................................................................................... 70	
  
Elemental	
  Analysis	
  (CHNS) ..................................................................................................................... 70	
  
Thermogravimatric	
  Analysis	
  (TGA) .................................................................................................... 71	
  
Pyrolysis	
  GC/MS........................................................................................................................................... 71	
  
Catalyst	
  Preparation................................................................................................................................... 72	
  
Electrocatalytic	
  Hydrogenation	
  of	
  EAP	
  Lignin ............................................................................... 72	
  
Size	
  Exclusion	
  Chromatography ........................................................................................................... 73	
  
Results	
  and	
  Discussion................................................................................................................................... 74	
  
HHV,	
  Elemental	
  Analysis	
  and	
  TGA ....................................................................................................... 74	
  
Pyrolysis	
  GC/MS........................................................................................................................................... 77	
  
Electrocatalytic	
  Hydrogenation	
  of	
  EAP	
  Lignin ............................................................................... 78	
  
Conclusion ........................................................................................................................................................... 79	
  
REFERENCES...................................................................................................................................................... 82	
  
Chapter	
  4	
  :	
  Conclusions	
  and	
  Future	
  Work.................................................................................85	
  
Conclusions ......................................................................................................................................................... 85	
  
Future	
  Work ....................................................................................................................................................... 86	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

vi	
  
	
  

	
  
LIST	
  OF	
  TABLES	
  	
  
Table	
  1.1:	
  Major	
  linkage	
  types	
  and	
  their	
  abundance	
  in	
  lignin	
  structure ...................................... 11	
  
Table	
  1.2:	
  Difference	
  in	
  properties	
  of	
  bio-­‐oil	
  and	
  fuel	
  oil	
  53 ............................................................... 16	
  
Table	
  1.3:	
  Electrocatalytic	
  reduction	
  of	
  various	
  substrates	
  using	
  different	
  catalysts ............ 21	
  
Table	
  2.1:	
  Scanning	
  electron	
  microscopy	
  elemental	
  analysis	
  using	
  EDX ..................................... 42	
  
Table	
  2.2:	
  Summary	
  table	
  of	
  yield	
  and	
  current	
  efficiency	
  of	
  ECH	
  of	
  methoxyphenols ........... 47	
  
Table	
  2.3:	
  Summary	
  table	
  of	
  selectivity	
  and	
  conversion	
  of	
  ECH	
  of	
  methoxyphenols.............. 48	
  
Table	
  2.4:	
  Summary	
  table	
  of	
  ECH	
  of	
  4-­‐phenoxyphenol	
  using	
  different	
  electrolytes ............... 52	
  
Table	
   2.5:	
   Summary	
   of	
   ECH	
   of	
   4-­‐phenoxyphenol	
   with	
   different	
   current	
   density	
   and	
  
substrate	
  concentration............................................................................................................................ 54	
  
Table	
  2.6:	
  Summary	
  table	
  of	
  catalyst	
  deactivation	
  study .................................................................... 57	
  
Table	
  3.1:	
  HHV	
  and	
  elemental	
  analysis	
  of	
  F3	
  and	
  F1	
  fraction ........................................................... 75	
  
Table	
  3.2:	
  Retention	
  times	
  of	
  products	
  from	
  Py/GC-­‐MS	
  of	
  F3	
  fraction ......................................... 78	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
vii	
  
	
  

	
  
LIST	
  OF	
  FIGURES	
  	
  
Figure	
  1.1:	
  Comparison	
  of	
  available	
  biomass,	
  carbon	
  and	
  energy	
  production	
  in	
  the	
  US	
  based	
  
on	
   predictions	
   by	
   the	
   U.S.	
   billion-­‐ton	
   study	
   update	
   vs.	
   U.S.	
   petroleum	
   consumption	
  
during	
  2013....................................................................................................................................................... 3	
  
Figure	
  1.2:	
  Three	
  monolignols	
  para-­‐coumaryl	
  alcohol,	
  coniferyl	
  alcohol,	
  sinapyl	
  alcohol...... 9	
  
Figure	
  1.3:	
  Electrocatalytic	
  hydrogenation	
  and	
  hydrogen	
  evolution	
  steps	
  66 ............................ 19	
  
Figure	
  2.1:	
  Overall	
  scheme	
  of	
  the	
  project	
  from	
  EAP	
  lignin	
  to	
  liquid	
  fuels.................................... 36	
  
Figure	
  2.2:	
  Dimers	
  a)	
  4-­‐phenoxyphenol	
  (4-­O-­5)	
  b)	
  Dimer#1	
  (β-­O-­4) ............................................ 37	
  
Figure	
  2.3:	
  Two	
  chambered	
  H-­‐cell	
  setup .................................................................................................... 39	
  
Figure	
  2.4:	
  X-­‐ray	
  dot	
  map	
  analysis	
  of	
  Ru/ACC	
  for	
  carbon	
  and	
  ruthenium	
  a)	
  carbon	
  cloth	
  b)	
  
ruthenium ....................................................................................................................................................... 42	
  
Figure	
  2.5:	
  Scanning	
  electron	
  microscopy	
  images	
  of	
  a)	
  unloaded	
  b)	
  ruthenium	
  loaded....... 43	
  
Figure	
  2.6:	
  Scanning	
  electron	
  microscopy	
  images	
  of	
  loaded	
  cloth	
  a)	
  100x	
  	
  b)	
  300x............... 43	
  
Figure	
   2.7:	
   Reaction	
   pathways	
   for	
   the	
   reduction	
   of	
   methoxycyclohexanol	
   to	
   cyclohexanol	
  
and	
  methoxycyclohexanol ....................................................................................................................... 45	
  
Figure	
  2.8:	
  Electrocatalytic	
  hydrogenation	
  and	
  hydrogen	
  evolution	
  steps	
  18 ............................ 45	
  
Figure	
   2.9:	
   	
   Product	
   yield,	
   amount	
   of	
   starting	
   material	
   left,	
   current	
   efficiency	
   and	
  
conversion	
  of	
  ECH	
  of	
  methoxyphenols .............................................................................................. 47	
  
Figure	
   2.10:	
   Conversion,	
   product	
   yield	
   and	
   depletion	
   of	
   starting	
   material	
   of	
   ECH	
   of	
   2-­‐
methoxyphenol............................................................................................................................................. 48	
  
Figure	
   2.11:	
   Conversion,	
   product	
   yield	
   and	
   depletion	
   of	
   starting	
   material	
   of	
   ECH	
   of	
   3-­‐
methoxyphenol............................................................................................................................................. 49	
  
Figure	
   2.12:	
   Conversion,	
   product	
   yield	
   and	
   depletion	
   of	
   starting	
   material	
   of	
   ECH	
   of	
   4-­‐
methoxyphenol............................................................................................................................................. 49	
  

viii	
  
	
  

	
  
Figure	
  2.13:	
  Suggested	
  reaction	
  pathway	
  for	
  ECH	
  of	
  4-­‐phenoxyphenol....................................... 52	
  
Figure	
  2.14:	
  Reaction	
  conditions	
  and	
  products	
  of	
  ECH	
  of	
  dimer	
  #1............................................... 55	
  
Figure	
  2.15:	
  Product	
  yield	
  (phenol	
  +	
  cyclohexanol)	
  for	
  catalyst	
  deactivation	
  test .................. 57	
  
Figure	
  2.16:	
  Current	
  efficiency	
  for	
  catalyst	
  deactivation	
  test............................................................ 58	
  
Figure	
  2.17:	
  Conversion	
  for	
  catalyst	
  deactivation	
  test ......................................................................... 58	
  
Figure	
   3.1:	
   Overall	
   project	
   scheme	
   from	
   biomass	
   harvesting	
   to	
   pretreatment	
   using	
  
extractive	
   ammonia	
   process	
   folowed	
   by	
   pyrolysis	
   and	
   electrocatalysis	
   to	
   upgrade	
   to	
  
valuable	
  procuscts....................................................................................................................................... 67	
  
Figure	
   3.2:	
   Method	
   used	
   to	
   produce	
   EAP	
   lignins.	
   	
   Lignins	
   are	
   present	
   in	
   oligomeric	
   and	
  
polymeric	
  forms	
  as	
  per	
  the	
  molecular	
  weights	
  of	
  each	
  fraction............................................. 69	
  
Figure	
  3.3:	
  Ethanol	
  soluble	
  F3	
  fraction	
  as	
  obtained	
  from	
  liquid	
  ammonia	
  after	
  precipication	
  
in	
  water	
  followed	
  by	
  solubilization	
  in	
  ethanol ............................................................................... 70	
  
Figure	
  3.4:	
  Two	
  chambered	
  H-­‐cell	
  setup .................................................................................................... 73	
  
Figure	
  3.5:	
  TGA	
  analysis	
  of	
  F3	
  fraction ........................................................................................................ 76	
  
Figure	
  3.6:	
  TGA	
  analysis	
  of	
  F1	
  fraction ........................................................................................................ 76	
  
Figure	
  3.7:	
  Py/GC	
  chromatogram	
  of	
  F3	
  fraction	
  with	
  peak	
  labels	
  outlined	
  in	
  Table	
  3.2....... 77	
  
	
  
	
  
	
  

ix	
  
	
  

	
  
Chapter	
  1	
  : Introduction	
  and	
  Background	
  	
  
Introduction	
  
The	
   use	
   of	
   fossil	
   fuels	
   for	
   the	
   production	
   of	
   energy	
   and	
   raw	
   materials	
   has	
   been	
  
providing	
  resources	
  for	
  daily	
  human	
  necessities	
  for	
  hundreds	
  of	
  years.	
  However,	
  there	
  are	
  
two	
  major	
  reasons	
  why	
  this	
  will	
  not	
  be	
  sustainable	
  in	
  the	
  future.	
  First	
  and	
  foremost	
  fossil	
  
fuels	
  are	
  limited	
  and	
  non-­‐renewable	
  since	
  they	
  take	
  millions	
  of	
  years	
  to	
  regenerate,	
  a	
  time	
  
frame	
   irrelevant	
   to	
   current	
   generations	
   of	
   mankind.	
   Second,	
   the	
   use	
   of	
   fossil	
   fuels	
  
contributes	
  to	
  rising	
  levels	
  of	
  greenhouse	
  gases,	
  an	
  issue	
  for	
  which	
  the	
  Intergovernmental	
  
Panel	
  on	
  Climate	
  Change	
  (IPCC)	
  implicated	
  humanity	
  in	
  2013.1	
  To	
  this	
  end,	
  the	
  use	
  of	
  fossil	
  
fuels	
   is	
   not	
   a	
   sustainable	
   form	
   of	
   energy	
   and	
   alternatives	
   should	
   be	
   considered.	
  	
  
Furthermore,	
   the	
   use	
   of	
   petroleum	
   creates	
   global	
   energy	
   dependence	
   and	
   all	
   the	
   economic	
  
and	
  political	
  issues	
  that	
  come	
  with	
  it.	
  The	
  U.S.,	
  for	
  example,	
  is	
  considered	
  to	
  be	
  one	
  of	
  the	
  
largest	
   consumers	
   of	
   petroleum	
   in	
   the	
   world,	
   reported	
   to	
   have	
   consumed	
   18.6	
   million	
  
barrels	
   of	
   petroleum	
   products	
   per	
   day	
   (MMbd)	
   in	
   2012.	
   According	
   to	
   the	
   Energy	
  
Information	
   Administration	
   (EIA)	
   about	
   40%	
   of	
   that	
   (7.4	
   MMbd)	
   was	
   imported	
   from	
  
abroad	
   so	
   the	
   U.S.	
   could	
   greatly	
   benefit	
   from	
   the	
   displacement	
   of	
   petroleum	
   with	
  
renewable	
   sources.2	
   To	
   achieve	
   such	
   a	
   goal,	
   the	
   Energy	
   Independence	
   and	
   Security	
   Act	
  
mandates	
   that	
   by	
   the	
   year	
   2022,	
   21	
   billion	
   gallons	
   of	
   advanced	
   biofuels	
   be	
   introduced	
   to	
  
displace	
  petroleum.3	
  To	
  this	
  end,	
  the	
  need	
  for	
  sustainable	
  sources	
  of	
  fuels	
  and	
  chemical	
  raw	
  
materials	
   that	
   are	
   environmentally	
   friendly	
   and	
   economically	
   feasible	
   has	
   been	
   a	
   driving	
  
force	
   for	
   the	
   conversion	
   of	
   biomass	
   to	
   liquid	
   fuels	
   and	
   value	
   added	
   products.	
   	
   Biomass	
   is	
  
considered	
   as	
   a	
   viable	
   alternative	
   due	
   to	
   its	
   potential	
   to	
   be	
   converted	
   to	
   hydrocarbon	
   fuels	
  

1	
  
	
  

	
  
and	
   its	
   ability	
   to	
   offset	
   the	
   CO2	
   emissions	
   due	
   to	
   plant	
   growth.4	
   According	
   to	
   the	
   2011	
  
Billion-­‐ton	
  Study	
  update,	
  biomass	
  has	
  been	
  used	
  as	
  feedstock	
  for	
  producing	
  and	
  supplying	
  
about	
   4%	
   of	
   the	
   total	
   U.S.	
   energy	
   requirements.5	
   Furthermore,	
   66.1%	
   of	
   the	
   renewable	
  
energy	
   in	
   the	
   European	
   Union	
   is	
   obtained	
   from	
   biomass,	
   which	
   is	
   more	
   than	
   the	
   amount	
  
provided	
   from	
   other	
   renewable	
   sources.6	
   Therefore	
   as	
   biomass	
   is	
   becoming	
   more	
   and	
  
more	
   important	
   as	
   an	
   alternative	
   energy	
   source,	
   advancements	
   in	
   conversion	
   processes	
  
could	
  be	
  very	
  beneficial.	
  	
  
Various	
  processes	
  can	
  be	
  used	
  for	
  the	
  conversion	
  of	
  biomass	
  into	
  biofuels,	
  unlocking	
  
the	
  energy	
  stored	
  within	
  the	
  bonds	
  that	
  hold	
  the	
  different	
  components	
  of	
  biomass	
  together.	
  
One	
  promising	
  process,	
  and	
  the	
  main	
  focus	
  of	
  this	
  review,	
  is	
  biomass	
  fast	
  pyrolysis	
  (BFP).	
  
As	
   its	
   name	
   implies	
   this	
   thermochemical	
   conversion	
   entails	
   rapid	
   heating	
   of	
   biomass	
   to	
  
relatively	
   high	
   temperatures	
   in	
   the	
   absence	
   of	
   oxygen.	
   BFP	
   produces	
   a	
   liquid	
   (bio-­‐oil),	
   a	
  
solid	
   (char)	
   and	
   gas	
   optimized	
   to	
   maximize	
   the	
   bio-­‐oil	
   fraction.	
   BFP	
   is	
   a	
   promising	
   path	
  
from	
   plant	
   matter	
   to	
   liquid	
   biofuels	
   and	
   raw	
   materials	
   for	
   value-­‐added	
   products	
   at	
   low	
  
cost.	
   7,8	
  However,	
  undesirable	
  properties	
  of	
  crude	
  bio-­‐oil	
  such	
  as	
  high	
  oxygen,	
  high	
  water	
  
content,	
   low	
   heating	
   value	
   and	
   chemical	
   instability7	
   prevent	
   it	
   from	
   being	
   commercially	
  
viable	
  drop-­‐in	
  petroleum	
  replacement	
  without	
  further	
  upgrading.	
  Furthermore,	
  due	
  to	
  its	
  
relatively	
  high	
  acid	
  content	
  bio-­‐oil	
  can	
  corrode	
  steel	
  engines,	
  pipelines	
  and	
  storage	
  tanks,	
  
making	
  it	
  incompatible	
  with	
  the	
  current	
  fuel	
  handling	
  and	
  use	
  technologies.7	
  Additionally,	
  
conversion	
   of	
   biomass	
   to	
   bio-­‐fuels	
   cannot	
   fully	
   displace	
   petroleum	
   fuels	
   as	
   biomass	
   falls	
  
short	
   in	
   terms	
   of	
   both	
   carbon	
   content	
   and	
   energy	
   content.	
   As	
   shown	
   in	
   Figure	
   1.1,	
   even	
  
under	
  the	
  best	
  of	
  scenarios,	
  the	
  biomass	
  that	
  is	
  reported	
  to	
  be	
  available	
  for	
  use	
  as	
  feedstock	
  
for	
   bio-­‐fuel	
   production	
   (1.3	
   billion	
   tons/year)	
   can	
   only	
   provide	
   520	
   millions	
   tons	
   of	
  

2	
  
	
  

	
  
carbon/year	
   and	
   19	
   billion	
   GJ	
   (giga	
   joules)	
   of	
   energy/year	
   vs.	
   860	
   million	
   tons	
   of	
   carbon	
  
and	
  42	
  billion	
  GJ	
  of	
  energy	
  per	
  year	
   that	
  can	
  be	
  provided	
  by	
  1	
  billion	
  tons	
  of	
  petroleum	
  per	
  
year.9	
  So	
  more	
  efficient	
  conversion	
  strategies	
  that	
  conserve	
  carbon	
  from	
  biomass	
  need	
  to	
  
be	
  explored	
  in	
  addition	
  to	
  increasing	
  the	
  energy	
  content	
  of	
  biomass-­‐derived	
  fuels	
  such	
  as	
  
bio-­‐oil	
   using	
   upgrading	
   strategies.	
   Therefore,	
   tackling	
   these	
   problems	
   requires	
   extensive	
  
study	
  and	
  understanding	
  of	
  the	
  effect	
  of	
  feed	
  material	
  composition,	
  biomass	
  pretreatment	
  
processes,	
  pyrolysis	
  process	
  parameters,	
  and	
  viable	
  upgrading	
  strategies.	
  	
  	
  

Energy	
  

19	
  x	
  109	
  GJ/year	
  	
  
42	
  x	
  109	
  GJ/year	
  	
  

Carbon	
  

520	
  x	
  106	
  tons	
  C/year	
  

Biomass	
  

860	
  x	
  106	
  tons	
  C/year	
  

Petrolem	
  

1.3	
  x	
  109	
  tons/year	
  
Mass	
  
1	
  x	
  109	
  tons/year	
  

	
  
Figure	
  1.1:	
  Comparison	
  of	
  available	
  biomass,	
  carbon	
  and	
  energy	
  production	
  in	
  the	
  US	
  based	
  
on	
  predictions	
  by	
  the	
  U.S.	
  billion-­‐ton	
  study	
  update	
  vs.	
  U.S.	
  petroleum	
  consumption	
  during	
  
2013	
  	
  
This	
  chapter	
  is	
  structured	
  to	
  cover	
  a	
  brief	
  analysis	
  of	
  the	
  current	
  energy	
  crisis	
  and	
  
biomass	
  as	
  a	
  possible	
  solution	
  to	
  this	
  issue.	
  Additionally,	
  the	
  advantages	
  and	
  the	
  potential	
  
of	
   utilizing	
   pretreatment	
   methods	
   such	
   as	
   extractive	
   ammonia	
   process	
   (EAP)	
   for	
   lignin	
  
extraction	
   is	
   covered.	
   	
   Last	
   but	
   not	
   least,	
   the	
   use	
   of	
   fast	
   pyrolysis	
   coupled	
   with	
  

3	
  
	
  

	
  
electrocatalysis	
  as	
  a	
  way	
  of	
  further	
  depolymerizing	
  and	
  upgrading	
  lignin	
  for	
  the	
  production	
  
of	
  a	
  viable	
  liquid	
  fuel	
  intermediate	
  is	
  reviewed.	
  	
  
Research	
  Objectives	
  	
  
1. Characterize	
  EAP	
  lignin	
  to	
  help	
  identify	
  the	
  potential	
  of	
  pretreated	
  biomass	
  lignin	
  as	
  
a	
  feedstock	
  for	
  liquid	
  fuel	
  production	
  via	
  fast	
  pyrolysis	
  
2. Examine	
  the	
  electrocatalysis	
  of	
  lignin-­derived	
  monomers	
  such	
  as	
  2-­‐methoxyphenol,	
  3-­‐
methoxyphenol	
  and	
  4-­‐methoxyphenol	
  
3. Study	
   the	
   use	
   of	
   electrocatalysis	
   for	
   model-­lignin	
   dimers	
   with	
   specific	
   linkages	
   to	
  
determine	
  its	
  effectiveness	
  for	
  cleaving	
  such	
  linkages.	
  	
  
4. Explore	
  direct	
  electrocatalysis	
  of	
  EAP	
  Lignin	
  to	
  gauge	
  the	
  potential	
  of	
  electrocatalysis	
  
as	
  a	
  method	
  for	
  bypassing	
  fast	
  pyrolysis	
  to	
  produce	
  stable	
  lignin	
  fragments.	
  	
  
Energy	
  Crisis	
  and	
  Environmental	
  Impact	
  	
  
Fossil	
  Fuel	
  Use	
  	
  
The	
   continued	
   consumption	
   of	
   fossil	
   fuels	
   as	
   a	
   source	
   of	
   energy	
   might	
   have	
   some	
  
major	
   impacts	
   related	
   to	
   energy	
   consumption	
   as	
   well	
   as	
   environmental	
   issues.	
   Energy	
  
consumption	
   is	
   projected	
   to	
   keep	
   increasing	
   through	
   2030;10	
   as	
   reported	
   by	
   Mason	
   in	
  
2007,	
  world	
  energy	
  consumption	
  was	
  growing	
  at	
  2%	
  per	
  year	
  and	
  if	
  it	
  continued	
  to	
  grow	
  at	
  
this	
   rate,	
   it	
   would	
   double	
   within	
   the	
   following	
   35	
   years.11	
   Furthermore,	
   according	
   to	
   the	
  
2013	
  International	
  Energy	
  Outlook	
  report	
  the	
  US	
  Energy	
  Information	
  Administration	
  (EIA)	
  
predicts	
   a	
   56%	
   increase	
   in	
   total	
   world	
   energy	
   consumption	
   from	
   524	
   quadrillion	
   Btu	
   in	
  
2010,	
  to	
  630	
  quadrillion	
  Btu	
  in	
  2020,	
  and	
  to	
  820	
  quadrillion	
  Btu	
  in	
  2040.12	
  In	
  conjunction	
  
with	
  increasing	
  energy	
  consumption,	
  energy	
  production	
  from	
  fossil	
  fuels	
  and	
  renewables	
  is	
  
4	
  
	
  

	
  
predicted	
  to	
  keep	
  increasing	
  for	
  the	
  next	
  30	
  years.10	
  	
  	
  The	
  EIA	
  reports	
  that	
  even	
  though	
  the	
  
supply	
   of	
   energy	
   from	
   rapidly	
   growing	
   renewable	
   sources	
   and	
   nuclear	
   power	
   are	
  
increasing	
   by	
   about	
   2.5%	
   per	
   year,	
   fossil	
   fuels	
   still	
   continue	
   to	
   dominate	
   the	
   energy	
   supply	
  
by	
   providing	
   about	
   80%	
   of	
   the	
   energy	
   use	
   through	
   2040.12	
   Although	
   there	
   are	
   no	
   clear	
  
predictions	
  of	
  when	
  fossil	
  fuels	
  will	
  be	
  completely	
  depleted,	
  some	
  studies	
  point	
  to	
  oil,	
  coal	
  
and	
  gas	
  predict	
  depletion	
  in	
  35,	
  107	
  and	
  37	
  years	
  respectively.	
   13	
  	
  So	
  more	
  efforts	
  need	
  to	
  
be	
  made	
  to	
  displace	
  fossils	
  with	
  renewable	
  sources.	
  	
  
Environmental	
  Impact	
  of	
  Climate	
  Change	
  	
  
In	
   addition	
   to	
   the	
   issues	
   related	
   to	
   depleting	
   fossil	
   reserves,	
   the	
   environmental	
  
impact	
  of	
  burning	
  fossil	
  fuels	
  for	
  energy	
  production	
  cannot	
  be	
  ignored.	
  Energy	
  production	
  
primarily	
   from	
   burning	
   fossil	
   fuels	
   is	
   the	
   main	
   contributor	
   to	
   increased	
   emission	
   of	
  
greenhouse	
  gases	
  (GHG)	
  such	
  as	
  CO2	
  into	
  the	
  atmosphere.	
   14	
  These	
  emissions,	
  in	
  turn,	
  are	
  
believed	
   to	
   be	
   related	
   to	
   global	
   temperature	
   increase,	
   which	
   induces	
   global	
   climate	
   change	
  
linking	
   future	
   energy	
   production	
   to	
   global	
   warming.14	
   Hence	
   the	
   warming	
   of	
   the	
   earth	
  
within	
  the	
  next	
  century	
  due	
  to	
  the	
  anthropogenic	
  greenhouse	
  emissions	
  from	
  fossil	
  use	
  is	
  
inevitable.	
   15	
   As	
   Reported	
   by	
   the	
   National	
   Oceanic	
   and	
   Atmospheric	
   Administration’s	
  
(NOAA)	
  Global	
  Greenhouse	
  Reference	
  Network,	
  the	
  average	
  CO2	
   level	
  measured	
  at	
  Mauna	
  
Loa	
  Hawaii	
  in	
  April	
  2014	
  was	
  401.30	
  ppm	
  as	
  compared	
  to	
  April	
  2013,	
  which	
  was	
  398.35	
  
ppm.16	
   Looking	
   at	
   the	
   trends	
   presented	
   by	
   NOAA	
   since	
   1960,	
   CO2	
   in	
   the	
   atmosphere	
   has	
  
gradually	
  increased.	
  	
  As	
  a	
  result	
  of	
  the	
  rise	
  in	
  CO2	
  emissions,	
  global	
  average	
  land	
  and	
  ocean	
  
surface	
   temperature	
   has	
   shown	
   an	
   increase	
   of	
   0.78	
   °C	
   when	
   comparing	
   the	
   averages	
  
between	
  1850-­‐1900	
  and	
  2003-­‐2012	
  period.	
  17	
  If	
  humans	
  continue	
  to	
  emit	
  GHGs	
  at	
  this	
  rate	
  

5	
  
	
  

	
  
it	
   is	
   predicted	
   that	
   the	
   global	
   temperatures	
   will	
   rise	
   and	
   could	
   have	
   dangerous	
  
anthropogenic	
  interferences	
  (DAI)	
  with	
  the	
  climate	
  system.18	
  The	
  ramifications	
  of	
  climate	
  
change	
   could	
   be	
   very	
   drastic	
   resulting	
   in	
   extreme	
   weather,	
   effects	
   on	
   human	
   health,	
  
increases	
  ocean	
  acidity	
  and	
  impacts	
  on	
  habitats.	
  
Social	
  Impacts	
  of	
  Climate	
  Change	
  	
  
As	
   climate	
   and	
   weather	
   conditions	
   dictate	
   much	
   of	
   our	
   daily	
   existence,	
   these	
  
environmental	
   and	
   climate	
   changes	
   in	
   turn	
   have	
   impacts	
   on	
   society	
   with	
   regards	
   to	
   our	
  
health,	
  food	
  and	
  water	
  supply,	
  energy,	
  transportation,	
  access	
  to	
  infrastructure,	
  etc.19	
  That	
  
stated,	
  due	
  to	
  geographic	
  location	
  and	
  economic	
  status,	
  certain	
  communities	
  or	
  groups	
  will	
  
likely	
   feel	
   the	
   impact	
   more	
   than	
   others.	
   	
   Those	
   that	
   have	
   fewer	
   or	
   limited	
   resources	
   will	
   be	
  
most	
   impacted	
   by	
   climate	
   change.20	
   Native	
   and	
   indigenous	
   communities	
   restricted	
   by	
  
various	
   geographical,	
   economical	
   and	
   cultural	
   boundaries,	
   and	
   populations	
   in	
   developing	
  
countries	
   that	
   have	
   weak	
   infrastructures	
   are	
   included	
   in	
   this	
   group.	
   21	
   In	
   most	
   of	
   these	
  
cases	
  certain	
  health	
  risks	
  that	
  are	
  climate	
  sensitive	
  such	
  as	
  diarrheal	
  diseases,	
  malnutrition,	
  
and	
  malaria	
  will	
  be	
  exacerbated	
  in	
  these	
  poor	
  areas	
  as	
  a	
  result	
  of	
  climate	
  change.	
  This	
  in	
  
turn	
   will	
   put	
   a	
   huge	
   dent	
   on	
   the	
   economics	
   of	
   the	
   health	
   sector	
   estimated	
   to	
   reach	
   US	
   $2-­‐4	
  
billion/year	
  by	
  2030.	
  22	
  
Considering	
   the	
   background	
   information	
   in	
   the	
   previous	
   paragraphs	
   (potential	
  
fossil	
   fuel	
   depletion,	
   global	
   climate	
   and	
   environmental	
   impacts	
   and	
   social	
   impacts	
   of	
  
deriving	
   energy	
   from	
   fossil	
   fuels),	
   the	
   World	
   Energy	
   Council	
   (WEC)	
   shows	
   that	
   many	
  
countries	
   are	
   choosing	
   to	
   reduce	
   their	
   dependence	
   on	
   fossil	
   fuels.10	
   This	
   is	
   leading	
   to	
  
tremendous	
   advancements	
   in	
   technologies	
   for	
   energy	
   production	
   from	
   renewable	
   sources.	
  

6	
  
	
  

	
  
According	
  to	
  the	
  IEA,	
  one	
  of	
  the	
  key	
  systems	
  that	
  will	
  revolutionize	
  the	
  future	
  is	
  production	
  
of	
   biofuels	
   to	
   supply	
   a	
   substantial	
   fraction	
   of	
   the	
   transportation	
   fuels	
   in	
   use	
   by	
   2030.10	
  
Accordingly,	
   lignocellulosic	
   resources	
   will	
   play	
   an	
   increasingly	
   important	
   role	
   in	
   the	
   future	
  
of	
  energy	
  production.23	
  	
  
Biomass	
  Components	
  
Optimization	
   of	
   the	
   biomass	
   depolymerization	
   process	
   requires	
   an	
   understanding	
   of	
  
biomass	
   itself.	
   The	
   term	
   biomass	
   is	
   used	
   to	
   describe	
   all	
   organic	
   material	
   which	
   includes	
  
plant-­‐based	
   matter	
   such	
   as	
   crops,	
   trees,	
   algae,	
   land-­‐	
   or	
   water-­‐based	
   plants	
   and	
   even	
  
organic	
   waste	
   and	
   animal-­‐based	
   matter.23	
   What	
   has	
   made	
   biomass	
   a	
   unique	
   source	
   of	
  
energy	
  is	
  the	
  stored	
  chemical	
  energy	
  that	
  is	
  derived	
  from	
  the	
  sun	
  and	
  stored	
  in	
  the	
  bonds	
  
within	
   the	
   organic	
   matter.23	
   Biomass	
   already	
   accounts	
   for	
   10-­‐14%	
   of	
   the	
   world’s	
   energy	
  
supply23	
   making	
   it	
   the	
   4th	
   largest	
   energy	
   source.24	
   Further	
   study	
   into	
   the	
   most	
   favorable	
  
biomass	
   properties	
   and	
   conversion	
   processes	
   could	
   elevate	
   the	
   potential	
   for	
   bioenergy	
  
production.	
  Ideal	
  biomass	
  properties	
  for	
  bioenergy	
  production	
  include	
  high	
  biomass	
  yield	
  
per	
   unit	
   land	
   area,	
   low	
   cost	
   and	
   energy	
   input	
   for	
   biomass	
   production	
   and	
   low	
   levels	
   of	
  
nutrients	
  and	
  contaminants	
  released	
  in	
  cultivation.23	
  Low	
  levels	
  of	
  water	
  consumption	
  are	
  
also	
   desirable.	
   The	
   fulfillment	
   of	
   the	
   above-­‐motioned	
   criteria	
   can	
   enhance	
   the	
   yields	
   and	
  
outcomes	
  of	
  the	
  various	
  conversion	
  methods	
  that	
  can	
  be	
  employed	
  to	
  break	
  down	
  biomass	
  
into	
  valuable	
  products	
  such	
  as	
  liquid	
  fuels	
  and	
  chemicals.	
  	
  	
  
In	
  order	
  to	
  understand	
  the	
  break	
  down	
  and	
  conversion	
  of	
  biomass,	
  an	
  understanding	
  of	
  
its	
   components	
   is	
   essential.	
   At	
   the	
   macromolecular	
   level	
   biomass	
   is	
   composed	
   of	
  
polysaccharides	
   (cellulose	
   and	
   hemicellulose)	
   and	
   lignin.	
   Although	
   it	
   is	
   highly	
   dependant	
  
on	
  the	
  type	
  of	
  biomass,	
  hemicellulose	
  accounts	
  for	
  about	
  20-­‐40	
  wt%,	
  cellulose	
  about	
  35-­‐60	
  
7	
  
	
  

	
  
wt%	
   and	
   lignin	
   about	
   10-­‐25	
   wt%.25	
   Cellulose	
   can	
   be	
   found	
   in	
   cell	
   walls	
   both	
   as	
   amorphous	
  
and	
  crystalline	
  polymers	
  made	
  from	
  glucose	
  building	
  units.	
  Similarly	
  hemicelluose	
  is	
  also	
  
an	
   amorphous	
   network	
   of	
   pentoses	
   and	
   hexoses.26	
   Lignin	
   is	
   a	
   highly	
   complex	
   branched	
  
network	
  constructed	
  from	
  monolignols.27	
  It	
  acts	
  as	
  the	
  binding	
  element	
  that	
  fills	
  the	
  empty	
  
spaces	
  in	
  plant	
  cell	
  walls	
  and	
  serves	
  to	
  hold	
  the	
  cell	
  wall	
  structure	
  together	
  in	
  addition	
  to	
  
providing	
  protection	
  against	
  pathogens.28	
  
Deconstructing	
   these	
   components	
   from	
   the	
   bulk	
   biomass	
   is	
   the	
   key	
   to	
   harnessing	
  
biomass-­‐derived	
   energy.	
   Due	
   to	
   the	
   relative	
   simplicity	
   of	
   the	
   structures	
   of	
   cellulose	
   and	
  
hemicellulose	
  compared	
  to	
  lignin,	
  these	
  polysaccharides	
  have	
  been	
  extensively	
  utilized	
  as	
  
feed	
   for	
   ethanol	
   production.	
   But	
   lignin’s	
   complexity	
   has	
   made	
   it	
   relatively	
   difficult	
   to	
  
depolymerize	
  for	
  use	
  as	
  an	
  efficient	
  source	
  of	
  biofuels.	
  In	
  businesses	
  such	
  as	
  the	
  pulp	
  and	
  
paper	
   industry,	
   lignin	
   is	
   often	
   a	
   byproduct	
   cellulose	
   extraction	
   and	
   is	
   usually	
   burned	
   for	
  
heat	
   or	
   discarded	
   as	
   a	
   waste	
   product.29	
   Only	
   2%	
   (about	
   one	
   million	
   tonnes)	
   of	
   the	
   lignin	
  
produced	
  as	
  the	
  byproduct	
  of	
  pulp	
  and	
  paper	
  processing	
  is	
  used	
  to	
  make	
  valuable	
  products,	
  
the	
   remainder	
   is	
   burned.30	
   Further	
   study	
   into	
   the	
   structure	
   and	
   depolymerization	
  
properties	
  of	
  lignin	
  is	
  needed	
  to	
  support	
  fuel	
  and	
  chemical	
  production.	
  	
  	
  	
  	
  	
  
Lignin:	
  Structure	
  	
  
The	
   definition	
   of	
   lignin	
   as	
   a	
   specific	
   compound	
   has	
   been	
   a	
   difficult	
   task	
   as	
   lignin	
   has	
  
different	
   structures	
   and	
   compositions	
   owing	
   to	
   the	
   randomness	
   of	
   the	
   polymerization	
  
process.	
  Lignin	
  is	
  therefore	
  considered	
  not	
  as	
  a	
  specific	
  compound	
  but	
  more	
  as	
  a	
  family	
  of	
  
cross-­‐linked	
  phenolic	
  polymers	
  found	
  in	
  secondary	
  cell	
  walls31	
  and	
  comprised	
  of	
  different	
  
building	
   blocks	
   connected	
   together	
   via	
   different	
   types	
   of	
   linkages.32	
   As	
   mentioned	
   above,	
  
lignin	
   is	
   composed	
   of	
   three	
   major	
   monolignols:	
   para-­‐coumaryl	
   alcohol,	
   coniferyl	
   alcohol	
  
8	
  
	
  

	
  
and	
   sinapyl	
   alcohol.	
   	
   Figure	
   1.2	
   shows	
   the	
   structures	
   of	
   these	
   compounds.	
   The	
   type	
   and	
  
amount	
   of	
   monolignols	
   present	
   in	
   lignin	
   is	
   different	
   for	
   different	
   types	
   of	
   biomass.	
  
Depending	
  on	
  whether	
  the	
  biomass	
  in	
  question	
  is	
  a	
  hardwood,	
  softwood	
  or	
  grass,	
  the	
  lignin	
  
content	
   and	
   composition	
   widely	
   vary.27	
   Lignin	
   from	
   softwood	
   is	
   primarily	
   made	
   of	
  
coniferyl	
   alcohol	
   units;	
   hardwood	
   lignin	
   is	
   mainly	
   made	
   of	
   sinapyl	
   alcohol	
   units	
   while	
  
grasses	
  contain	
  all	
  three	
  monolignols.	
  33	
  	
  
	
  
	
  
	
  
	
  
	
  	
  
Figure	
  1.2:	
  Three	
  monolignols	
  para-­‐coumaryl	
  alcohol,	
  coniferyl	
  alcohol,	
  sinapyl	
  alcohol	
  
The	
  monolignol	
  precursors	
  are	
  proposed	
  to	
  polymerize	
  via	
  random	
  radical	
  coupling	
  to	
  
form	
   dimers	
   and	
   higher	
   oligomers	
   by	
   addition	
   of	
   free	
   radical	
   monomers	
   to	
   the	
   existing	
  
dimer	
  or	
  oligomers.34	
  These	
  result	
  in	
  linkages	
  such	
  as	
  β-­‐O-­‐4,	
  β-­‐O-­‐5	
  and	
  β-­‐β	
  (Table	
  1.1).35,	
  36	
  
In	
   other	
   cases,	
   cross	
   coupling	
   of	
   two	
   already	
   forming	
   lignin	
   polymers	
   can	
   also	
   occur	
  
whereby	
  two	
  free	
  phenolic	
  guaiacyl	
  and	
  syringyl	
  units	
  join	
  together	
  to	
  form	
  such	
  linkages	
  
as	
  4-­‐O-­‐5	
  and	
  5-­‐5.	
   37	
  Table	
  1.1	
  shows	
  the	
  list	
  of	
  known	
  common	
  linkages	
  in	
  lignin	
  and	
  their	
  
relative	
  abundance	
  in	
  hardwoods	
  and	
  softwoods.	
  As	
  can	
  be	
  seen	
  from	
  these	
  numbers,	
  the	
  
most	
   abundant	
   and	
   dominant	
   type	
   tends	
   to	
   be	
   β-­‐O-­‐4	
   linkages.	
   The	
   exact	
   structure	
   of	
   the	
  
lignin	
  network	
  is	
  difficult	
  to	
  clearly	
  define,	
  as	
  the	
  structural	
  makeup	
  of	
  lignin	
  and	
  the	
  type	
  
of	
   monolignols	
   present	
   in	
   different	
   biomass	
   are	
   different.	
   Furthermore,	
   the	
   processes	
   used	
  

9	
  
	
  

	
  
for	
  depolymerization	
  and	
  isolation	
  of	
  lignin	
  components	
  can	
  greatly	
  influence	
  the	
  makeup	
  
and	
  bonding	
  arrangements	
  of	
  the	
  resulting	
  products.	
  38	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

10	
  
	
  

	
  
Table	
  1.1:	
  Major	
  linkage	
  types	
  and	
  their	
  abundance	
  in	
  lignin	
  structure	
  
Linkages	
  
Structures26,	
  28	
  
Abundance	
  (%)26,	
  28	
  

45-­‐50	
  (soft	
  wood)	
  
60-­‐62	
  (hardwood)	
  

β-­‐O-­‐4	
  
	
  

6-­‐8	
  (softwood)	
  
6-­‐8	
  (hardwood)	
  

α-­‐O-­‐4	
  
	
  

4-­‐7	
  (softwood)	
  
6.5-­‐9	
  (hardwood)	
  

4-­‐O-­‐5	
  
	
  

1-­‐9	
  (softwood)	
  
1-­‐7	
  (hardwood)	
  

β-­‐1	
  
	
  

19-­‐27	
  (softwood)	
  
3-­‐9	
  (hardwood)	
  

5-­‐5	
  
	
  

9-­‐12	
  (softwood)	
  
3-­‐11	
  (hardwood)	
  
	
  

β-­‐5	
  
	
  

2-­‐4	
  (softwood)	
  
3-­‐12	
  (hardwood)	
  

β-­‐β	
  
	
  

11	
  
	
  

	
  
Lignin:	
  Isolation	
  Processes	
  	
  
Biomass	
   pretreatment	
   methods	
   are	
   often	
   used	
   prior	
   to	
   conversion	
   to	
   extract	
   and	
  
isolate	
   the	
   different	
   components	
   of	
   biomass.	
   In	
   cellulosic	
   ethanol	
   production	
   processes	
  
pretreatments	
   is	
   essential	
   to	
   free	
   up	
   cellulose	
   from	
   the	
   hemicellulose	
   and	
   lignin	
   matrix,	
  
reduce	
   cellulose	
   crystallinity,	
   hydrolyze	
   hemicellulose,	
   and	
   enhance	
   the	
   porosity	
   of	
  
biomass.39-­‐41	
   Physical,	
   chemical,	
   biological	
   or	
   physicochemical	
   pretreatment	
   methods	
   can	
  
be	
   applied	
   as	
   a	
   way	
   of	
   preparing	
   biomass	
   for	
   further	
   conversion.42	
   Physical	
   methods	
  
usually	
   include	
   size	
   reduction,	
   via	
   grinding,	
   to	
   enhance	
   cellulose	
   decrystallization	
   and	
  
improve	
   heat	
   or	
   mass	
   transfer	
   during	
   conversion	
   processes.43	
   Chemical	
   pretreatments	
  
such	
   as	
   ozonolysis,44	
   acid	
   hydrolysis,	
   alkaline	
   hydrolysis,	
   oxidative	
   delignification	
   and	
  
organosolv	
   processes	
   all	
   make	
   use	
   of	
   different	
   chemicals	
   and	
   solvents	
   to	
   solubilize	
   lignin	
  
and	
   hemicellulose	
   while	
   freeing	
   up	
   cellulose	
   for	
   enzymatic	
   hydrolysis.40,	
  

45	
  

Biological	
  

pretreatment	
   implements	
   the	
   use	
   of	
   microorganisms	
   such	
   as	
   white-­‐rot	
   and	
   brown-­‐rot	
  
fungi	
   to	
   degrade	
   lignin.39,	
   40	
   Physicochemical	
   processes	
   such	
   as	
   steam	
   explosion	
   and	
   CO2	
  
explosion	
   expose	
   biomass	
   to	
   steam	
   and	
   CO2	
   respectively	
   at	
   high	
   pressure	
   followed	
   by	
   a	
  
sudden	
   pressure	
   drop.42,	
   46	
   These	
   processes	
   result	
   in	
   the	
   explosion	
   of	
   the	
   biomass	
   fibers	
  
making	
  cellulose	
  more	
  accessible	
  to	
  enzymatic	
  hydrolysis	
  by	
  degrading	
  hemicellulose	
  and	
  
transforming	
  lignin.	
  39	
  	
  
Ammonia	
   fiber	
   explosion	
   (AFEX)	
   is	
   another	
   physicochemical	
   process	
   that	
   is	
   of	
  
interest	
  to	
  this	
  group.	
  	
  AFEX	
  is	
  considered	
  to	
  have	
  good	
  potential	
  as	
  a	
  pretreatment	
  method	
  
for	
  biofuel	
  production	
  as	
  it	
  results	
  in	
  the	
  decompression	
  of	
  biomass	
  fibers.39,	
  47	
  During	
  the	
  
AFEX	
  pretreatment	
  process,	
  liquid	
  ammonia	
  is	
  added	
  to	
  biomass	
  at	
  pressures	
  of	
  100-­‐400	
  
psi	
  and	
  temperatures	
  of	
  70-­‐200	
  °C.	
  	
  The	
  system	
  is	
  then	
  rapidly	
  depressurized	
  resulting	
  in	
  
12	
  
	
  

	
  
the	
   explosion	
   of	
   the	
   biomass	
   fibers	
   causing	
   cellulose	
   decrystallization,	
   hemicellulose	
  
hydrolysis	
  and	
  lignin	
  depolymerization.47-­‐50	
   AFEX	
  is	
  ideal	
  for	
  cellulosic	
  ethanol	
  production	
  
as	
  it	
  enhances	
  feedstock	
  digestibility	
  by	
  increasing	
  the	
  surface	
  area	
  available	
  for	
  digestion	
  
(increasing	
  biomass	
  porosity)	
  and	
  by	
  transforming	
  the	
  lignin	
  for	
  better	
  access	
  to	
  cellulose	
  
and	
   hemicelluose.49	
   As	
   cellulose	
   and	
   hemicellulose	
   are	
   made	
   accessible	
   for	
   enzymatic	
  
hydrolysis,	
   lignin	
   can	
   further	
   be	
   extracted	
   and	
   is	
   often	
   discarded	
   as	
   a	
   waste	
   product	
   or	
  
burned	
  for	
  heat.40	
  Ideally	
  this	
  extracted	
   lignin	
  itself	
  has	
  potential	
  to	
  be	
  used	
  as	
  a	
  feedstock	
  
for	
   other	
   conversion	
   processes	
   such	
   as	
   fast	
   pyrolysis,	
   which	
   has	
   the	
   ability	
   to	
   further	
  
degrade	
  and	
  depolymerize	
  large	
  lignin	
  fractions.	
  
Fast	
  pyrolysis	
  as	
  a	
  Depolymerization	
  Process	
  	
  
The	
   selection	
   of	
   what	
   process	
   to	
   use	
   for	
   biomass	
   conversion	
   is	
   dependent	
   upon	
  
various	
   factors	
   such	
   as	
   the	
   type	
   of	
   biomass	
   used,	
   environmental	
   standards,	
   economic	
  
conditions	
   and	
   the	
   energy	
   value	
   of	
   the	
   fuel	
   produced	
   via	
   certain	
   conversion	
   methods.51	
  
There	
   are	
   three	
   main	
   processes	
   utilized	
   for	
   biomass	
   energy	
   production:	
   thermochemical	
  
conversion,	
   biochemical	
   conversion	
   and	
   mechanical	
   extraction	
   with	
   esterification.51	
  
Biochemical	
   conversion	
   can	
   be	
   further	
   subdivided	
   in	
   to	
   digestion	
   and	
   fermentation	
   and	
  
thermochemical	
  conversion	
  can	
  be	
  subdivided	
  into	
  combustion,	
  pyrolysis,	
  gasification	
  and	
  
liquefaction.51	
   Direct	
   combustion	
   of	
   the	
   biomass	
   can	
   produce	
   steam	
   for	
   electrical	
   power	
  
generation;	
   gaseous	
   fuel	
   can	
   be	
   produced	
   through	
   gasification	
   to	
   be	
   used	
   in	
   combustion	
   or	
  
to	
  drive	
  engine	
  turbines;	
  and	
  liquid	
  fuel	
  can	
  be	
  made	
  through	
  fast	
  pyrolysis,	
  which	
  can	
  then	
  
be	
   used	
   in	
   a	
   range	
   of	
   different	
   applications.8	
   Compared	
   to	
   various	
   other	
   conversion	
  
technologies	
  for	
  liquid	
  fuel	
  production,	
  fast	
  pyrolysis	
  has	
  been	
  developing	
  rapidly	
  due	
  to	
  its	
  
potential	
  for	
  providing	
  alternative	
  ways	
  for	
  producing	
  liquid	
  fuels.4,52	
  The	
  liquid	
  fuel	
  from	
  
13	
  
	
  

	
  
pyrolysis,	
   with	
   some	
   form	
   of	
   catalytic	
   upgrading,	
   has	
   the	
   potential	
   to	
   be	
   used	
   in	
   engines,	
  
turbines	
   and	
   boilers	
   to	
   produce	
   mechanical	
   work,	
   heat	
   and	
   power.	
   	
   	
   Solvent	
   extraction	
   can	
  
also	
   be	
   used	
   to	
   produce	
   bio-­‐based	
   chemicals.	
   	
   As	
   the	
   main	
   focus	
   in	
   this	
   study	
   is	
   the	
  
depolymerization	
  of	
  lignin,	
  which	
  is	
  traditionally	
  difficult	
  to	
  break	
  down,	
  thermochemical	
  
conversion	
  becomes	
  a	
  potential	
  option.	
  	
  
Fast	
   pyrolysis	
   involves	
   rapidly	
   heating	
   biomass	
   to	
   temperatures	
   between	
   400	
   °C	
  
and	
  600°C	
  in	
  the	
  absence	
  of	
  oxygen.8	
  The	
  decomposition	
  of	
  biomass	
  during	
  fast	
  pyrolysis	
  
generates	
  three	
  major	
  products,	
  a	
  liquid	
  referred	
  to	
  as	
  bio-­‐oil	
  (~70%),	
  a	
  solid	
  referred	
  to	
  as	
  
biochar	
   (~15%),	
   and	
   a	
   gas	
   (~15%)	
   rich	
   in	
   molecular	
   hydrogen,	
   carbon	
   oxides	
   and	
   light	
  
organics.	
   The	
   product	
   yield	
   and	
   quality	
   of	
   the	
   products	
   of	
   fast	
   pyrolysis	
   are	
   highly	
  
dependent	
   on	
   temperature,	
   heating	
   rate	
   and	
   pressure.7	
   Each	
   component	
   of	
   biomass	
  
degrades	
   and	
   decomposes	
   to	
   a	
   different	
   extent	
   under	
   different	
   heating	
   conditions	
   during	
  
fast	
   pyrolysis.8	
   For	
   example,	
   lignin	
   decomposes	
   over	
   a	
   wide	
   temperature	
   range	
   when	
  
compared	
  to	
  cellulose	
  while	
  hemicellulose	
  degrades	
  fast	
  in	
  a	
  narrower	
  temperature	
  range.8	
  
So	
   temperature	
   and	
   residence	
   time	
   are	
   two	
   very	
   important	
   parameters	
   that	
   need	
   to	
   be	
  
controlled	
  and	
  studied	
  in	
  the	
  production	
  of	
  bio-­‐oil	
  from	
  lignin.	
  	
  
Liquid	
  fuel	
  production	
  also	
  requires	
  very	
  low	
  vapor	
  residence	
  time	
  in	
  the	
  range	
  of	
  1-­‐
5	
   seconds	
   at	
   temperatures	
   of	
   up	
   to	
   500	
   °C.8	
   Keeping	
   the	
   residence	
   time	
   as	
   low	
   as	
   1	
   second	
  
helps	
   in	
   avoiding	
   secondary	
   reactions	
   and	
   improves	
   the	
   liquid	
   product	
   yield.	
   	
   At	
   larger	
  
vapor	
   residence	
   time	
   and	
   high	
   temperature,	
   secondary	
   cracking	
   of	
   the	
   primary	
   products	
  
will	
   result	
   in	
   reduced	
   liquid	
   products.8	
   In	
   addition,	
   low	
   temperature	
   (>400	
   °C)	
   leads	
   to	
  
condensation	
  reactions	
  and	
  formation	
  of	
  lower	
  molecular	
  weight	
  liquids,	
  which	
  can	
  further	
  
react.	
   8	
   It	
   is	
   important	
   to	
   understand	
   that	
   fast	
   pyrolysis	
   requires	
   high	
   heating	
   and	
   heat	
  
14	
  
	
  

	
  
transfer	
  rates,	
  a	
  controlled	
  temperature	
  of	
  about	
  500	
  °C,	
  low	
  residence	
  time	
  of	
  less	
  than	
  2	
  
seconds	
  and	
  rapid	
  cooling	
  of	
  the	
  vapors	
  produced	
  to	
  obtain	
  bio-­‐oil.	
  7,	
  8	
  	
  
Characteristics	
  of	
  Bio-­oil	
  
Bio-­‐based	
  fuels,	
  such	
  as	
  those	
  derived	
  from	
  bio-­‐oil,	
  are	
  considered	
  to	
  be	
  better	
  for	
  
the	
   environment	
   than	
   fossil	
   fuels	
   as	
   they	
   are	
   carbon	
   neutral	
   and	
   have	
   low	
   sulfur	
   content.53	
  
In	
  addition,	
  bio-­‐oil	
  can	
  easily	
  be	
  stored	
  and	
  transported	
  and	
  has	
  potential	
  to	
  be	
  used	
  for	
  the	
  
production	
  of	
  other	
  chemical	
  products.	
  But	
  before	
  bio-­‐oil	
  can	
  be	
  produced	
  and	
  used	
  on	
  a	
  
large	
   scale,	
   there	
   are	
   some	
   obstacles	
   that	
   need	
   to	
   be	
   overcome.	
   Bio-­‐oil	
   is	
   comprised	
   of	
  
oxygenated	
  organic	
  compounds	
  and	
  is	
  thus	
  not	
  as	
  chemically	
  reduced	
  as	
  petroleum-­‐based	
  
fuel.	
   Most	
   of	
   the	
   400	
   identified	
   organic	
   compounds54	
   in	
   bio-­‐oil	
   contain	
   35-­‐40	
   wt%	
  
oxygen.53	
  This	
  is	
  due	
  to	
  high	
  oxygen	
  content	
  of	
  biomass	
  that	
  originates	
  from	
  carbon-­‐oxygen	
  
(C=O)	
   bonds.55	
   From	
   a	
   synthetic	
   standpoint,	
   C=O	
   bonds	
   are	
   good	
   junction	
   points	
   for	
   the	
  
propagation	
   (polymerization)	
   of	
   carbohydrates	
   to	
   form	
   cellulose	
   and	
   hemicellulose	
   and	
  
monolignols	
  to	
  form	
  lignin.55	
  From	
  a	
  conversion	
  standpoint,	
  breaking	
  these	
  junction	
  points	
  
provides	
   the	
   key	
   to	
   depolymerizing	
   these	
   large	
   molecules	
   to	
   smaller	
   more	
   useful	
  
compounds.	
   After	
   pyrolysis,	
   the	
   class	
   of	
   fragments	
   that	
   are	
   formed	
   such	
   as	
   aldehydes,	
  
alcohols,	
   carbohydrates,	
   furans,	
   ketones,	
   and	
   phenolics	
   tend	
   to	
   retain	
   these	
   oxygens	
  
creating	
   undesirable	
   properties	
   in	
   bio-­‐oil.	
   The	
   stability	
   of	
   bio-­‐oil	
   is	
   questionable,	
   as	
   the	
  
above-­‐mentioned	
   components	
   tend	
   to	
   react	
   during	
   long-­‐term	
   storage	
   to	
   form	
   sludge.	
   For	
  
example	
   phenolics	
   and	
   aldehydes	
   react	
   to	
   form	
   resins	
   and	
   water.54	
   In	
   addition	
   to	
   these	
  
compounds	
   in	
   bio-­‐oil	
   being	
   reactive,	
   bio-­‐oil	
   is	
   also	
   corrosive	
   due	
   to	
   its	
   high	
   organic	
   acid	
  
content	
   (7-­‐12	
   wt%).7	
   The	
   retention	
   of	
   oxygen	
   from	
   the	
   feedstock	
   also	
   accounts	
   for	
   the	
   low	
  
higher	
  heating	
  value	
  (HHV)	
  of	
  bio-­‐oil.7	
  Furthermore,	
  the	
  high	
  water	
  content	
  that	
  is	
  retained	
  
15	
  
	
  

	
  
from	
   the	
   feedstock	
   (15-­‐30	
   wt%)	
   gives	
   bio-­‐oil	
   some	
   negative	
   attributes.	
   For	
   instance,	
   the	
  
presence	
  of	
  water	
  contributes	
  to	
  the	
  low	
  heating	
  value,	
  the	
  increase	
  in	
  ignition	
  delay,	
  the	
  
reduced	
  combustion	
  rates	
  and	
  phase	
  separation	
  of	
  the	
  bio-­‐oil	
  all	
  undesirable	
  features.7	
  Bio-­‐
oil	
   can	
   also	
   contain	
   char	
   particle	
   that	
   can	
   clog	
   and	
   erode	
   injector	
   and	
   turbine	
   blades.7	
  	
  	
  
Table	
   1.2,	
   adapted	
   from	
   Czernik	
   et	
   al.	
   summarizes	
   some	
   of	
   the	
   properties	
   of	
   bio-­‐oil	
   against	
  
the	
   corresponding	
   conventional	
   fuel	
   oil	
   properties.53	
   As	
   can	
   be	
   seen	
   from	
   this	
   table,	
   bio-­‐oil	
  
falls	
   short	
   in	
   several	
   categories	
   as	
   compared	
   to	
   crude	
   oil.	
   	
   These	
   properties	
   suggest	
   that	
  
catalysis	
   is	
   therefore	
   needed	
   to	
   upgrade	
   this	
   product	
   to	
   a	
   reactively	
   stable	
   fuel	
   that	
   is	
  
compatible	
  with	
  steel	
  tanks	
  and	
  pipes.	
  56	
  
Table	
  1.2:	
  Difference	
  in	
  properties	
  of	
  bio-­‐oil	
  and	
  fuel	
  oil	
  53	
  
Physical	
  Properties	
  
Bio-­oil	
  
Heavy	
  fuel	
  oil	
  
Moisture	
  content	
  (wt%)	
  

15-­‐30	
  

0.1	
  

pH	
  

2.5	
  

-­‐	
  

Specific	
  gravity	
  

1.2	
  

0.94	
  

Elemental	
  composition	
  (wt%)	
  

	
  

	
  

C	
  

54-­‐58	
  

85	
  

H	
  

5.5-­‐7.0	
  

11	
  

O	
  

35-­‐40	
  

1.0	
  

N	
  

0-­‐0.2	
  

0.3	
  

Ash	
  

0-­‐0.2	
  

0.1	
  

HHV	
  MJ/Kg	
  

16-­‐19	
  

40	
  

Viscosity	
  (@	
  50	
  °C	
  cP)	
  

40-­‐100	
  

180	
  

	
  
Research	
   suggests	
   that	
   with	
   chemical	
   upgrading,	
   utilization	
   of	
   better	
   filtration	
  
processes	
   and	
   certain	
   modifications	
   of	
   equipment	
   such	
   as	
   diesel	
   engines	
   and	
   boilers,	
   the	
  
use	
   of	
   bio-­‐oil	
   on	
   a	
   commercial	
   level	
   could	
   be	
   feasible.8	
   In	
   order	
   to	
   improve	
   chemical	
  

16	
  
	
  

	
  
upgrading,	
   a	
   better	
   understanding	
   of	
   the	
   chemical	
   mechanisms	
   of	
   pyrolysis	
   and	
   the	
   nature	
  
of	
  the	
  products	
  formed	
  during	
  pyrolysis	
  are	
  needed.	
  	
  The	
  next	
  section	
  will	
  describe	
   the	
  use	
  
of	
  electrocatlytic	
  hydrogenation	
  and	
  deoxygenation	
  as	
  a	
  possible	
  way	
  of	
  upgrading	
  bio-­‐oil.	
  	
  
Bio-­oil	
  Upgrading	
  using	
  Electrocatalytic	
  Hydrogenation	
  	
  	
  
Classical	
   catalytic	
   processes	
   such	
   as	
   those	
   used	
   in	
   the	
   petroleum	
   industry	
   can	
   be	
  
employed	
   to	
   upgrade	
   bio-­‐oil	
   to	
   aromatics.	
   These	
   processes	
   include	
   the	
   use	
   of	
   different	
  
catalysts	
   at	
   severe	
   conditions	
   such	
   as	
   high	
   temperatures	
   and	
   pressures.	
   Furthermore,	
  
hydrogen	
   has	
   to	
   be	
   supplied	
   to	
   enable	
   catalytic	
   hydrogenation	
   and	
   deoxygenation.	
   Such	
  
processes	
   incur	
   both	
   capital	
   and	
   operating	
   costs	
   due	
   to	
   the	
   equipment	
   and	
   energy	
   needs	
  
for	
   working	
   with	
   pressurized	
   hydrogen	
   at	
   high	
   temperatures,	
   as	
   well	
   as	
   the	
   safety	
  
measures	
   needed	
   for	
   these	
   relatively	
   dangerous	
   conditions.	
   	
   Under	
   these	
   sever	
   reactions	
  
conditions,	
  catalyst	
  deactivation	
  may	
  occur	
  due	
  to	
  coke	
  formation	
  blocking	
  active	
  sites	
  on	
  
the	
   catalyst	
   surface	
   and	
   inhibiting	
   of	
   metal-­‐substrate	
   interactions.57,58	
   Electrochemical	
  
upgrading	
   offers	
   an	
   alternative	
   whereby	
   mild	
   conditions	
   (low	
   temperature	
   and	
  
atmospheric	
   pressure)	
   are	
   used	
   to	
   achieve	
   hydrogenation	
   and	
   deoxygenation.59	
   This	
  
method	
  offers	
  certain	
  advantages	
  over	
  catalytic	
  hydrogenation;	
  as	
  the	
  hydrogen	
  needed	
  for	
  
reduction	
   is	
   produced	
   in	
   situ	
   in	
   ECH,	
   avoiding	
   the	
   kinetic	
   barrier	
   related	
   to	
   hydrogen	
  
dissociation.60	
  Additionally,	
  mass	
  transport	
  of	
  hydrogen	
  gas	
  is	
  also	
  avoided	
  in	
  ECH.60	
  Even	
  
catalyst	
  poisoning	
  is	
  avoided	
  due	
  to	
  the	
  cathodic	
  potential	
  that	
  can	
  prevent	
  the	
  adsorption	
  
of	
  poisons.	
  60	
  
As	
   shown	
   in	
   Figure	
   1.3,	
   electrocatalytic	
   hydrogentaion	
   occurs	
   via	
   a	
   multistep	
  
process	
   whereby	
   the	
   electroreduction	
   of	
   water	
   occurs	
   on	
   the	
   catalyst	
   surface	
   in	
   the	
  
cathode	
  compartment	
  producing	
  hydrogen	
  (a).	
  The	
  organic	
  substrate	
  also	
  adsorbed	
  on	
  to	
  
17	
  
	
  

	
  
the	
  catalyst	
  surface	
  forming	
  a	
  metal	
  substrate	
  complex	
  ([X=Y]M)	
  (b).	
  The	
  metal/hydrogen	
  
([H]M)	
   complex	
   that	
   is	
   formed	
   on	
   the	
   catalyst	
   then	
   interacts	
   with	
   the	
   neighboring	
  
substrate/metal	
   ([X=Y]M)	
   complex	
   on	
   the	
   catalyst	
   causing	
   reduction	
   of	
   the	
   organic	
  
substrate	
   (c).	
   The	
   reduced	
   substrate	
   then	
   desorbs	
   from	
   the	
   catalyst	
   (d).	
   Hydrogen	
  
evolution	
   also	
   occurs	
   when	
   hydrogen	
   desorbs	
   from	
   the	
   catalyst	
   surface	
   (d,e).	
   60-­‐63,64	
   This	
  
hydrogen	
  evolution	
  process	
  (e,f)	
  competes	
  with	
  the	
  hydrogenation	
  process	
  (c).	
  	
  
The	
   performance	
   of	
   electrocatalysis	
   is	
   determined	
   by	
   computing	
   the	
   current	
  
efficiency,	
  which	
  is	
  defined	
  as	
  the	
  fraction	
  of	
  charge	
  passed	
  that,	
  goes	
  towards	
  producing	
  
the	
   desired	
   products.	
   	
   Competition	
   between	
   hydrogen	
   evolution	
   and	
   substrate	
   reduction	
  
results	
   in	
   low	
   current	
   efficiency.60	
   The	
   rates	
   of	
   the	
   two	
   processes	
   are	
   in	
   turn	
   influenced	
   by	
  
several	
  other	
  factors	
  such	
  as:	
  bond	
  strength	
  of	
  the	
  substrate	
  that	
  is	
  being	
  reduced,	
  rate	
  and	
  
probability	
   of	
   adsorption	
   of	
   the	
   substrate	
   (substrate	
   concentration)64	
   and	
   strength	
   of	
  
bonding	
  of	
  hydrogen	
  to	
  the	
  catalyst	
  surface60	
  and	
  current	
  density65	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

18	
  
	
  

	
  
	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
Figure	
  1.3:	
  Electrocatalytic	
  hydrogenation	
  and	
  hydrogen	
  evolution	
  steps	
  66	
  
Several	
   materials	
   have	
   been	
   studied	
   for	
   use	
   as	
   electrode	
   materials	
   for	
   ECH	
   based	
  
both	
   on	
   their	
   ability	
   to	
   produce	
   molecular	
   hydrogen	
   and	
   their	
   potential	
   to	
   produce	
   the	
  
desired	
   products	
   with	
   high	
   selectivity.67	
   In	
   conjunction,	
   several	
   studies	
   on	
   different	
  
substrates	
   and	
   model	
   compounds	
   have	
   been	
   conducted	
   (Table	
   1.3).	
   	
   Earlier	
   studies	
  
included	
   the	
   use	
   of	
   noble	
   metals	
   such	
   as	
   Pt,	
   Rh	
   and	
   Pd.	
   In	
   an	
   effort	
   to	
   move	
   away	
   from	
  
expensive	
   metals,	
   more	
   recent	
   studies	
   have	
   focused	
   on	
   catalysts	
   such	
   as	
   Raney	
   nickel,	
  
nickel	
  metal	
  powders	
  or	
  metals	
  supported	
  on	
  carbon.67	
  	
  
As	
   outlined	
   in	
   Table	
   1.3,	
   studies	
   on	
   bio-­‐oil-­‐derived	
   monomers	
   such	
   as	
   guaiacol,	
  
phenol,	
  and	
  syringol	
  have	
  shown	
  promising	
  results	
  for	
  the	
  potential	
  of	
  ECH	
  for	
  upgrading	
  
these	
  bio-­‐oil	
  components	
  to	
  more	
  stable	
  forms.	
  Studies	
  on	
  lignin-­‐derived	
  bio-­‐oil	
  monomers	
  
done	
   by	
   Li	
   et	
   al.	
   have	
   shown	
   successful	
   reduction	
   of	
   phenol,	
   guaiacol	
   and	
   syringol	
   using	
  
ruthenium	
   loaded	
   on	
   activated	
   carbon	
   cloth	
   (Ru/ACC).	
   68	
   Further	
   studies	
   in	
   this	
   area	
   are	
  
19	
  
	
  

	
  
needed	
  to	
  explore	
  the	
  effectiveness	
  of	
  this	
  catalyst	
  to	
  reduce	
  various	
  other	
  lignin-­‐derived	
  
monomers.	
  Additionally	
  in	
  these	
  studies,	
  modest	
  current	
  efficiencies	
  of	
  no	
  more	
  than	
  30%	
  
were	
   reported	
   due	
   the	
   hydrogen	
   evolution	
   reaction	
   competition	
   for	
   the	
   total	
   charge	
  
passed.	
   Exploration	
   of	
   different	
   conditions	
   to	
   help	
   improve	
   the	
   current	
   efficiency	
   value	
  
could	
  be	
  very	
  beneficial.	
  	
  
	
  Studies	
  on	
  lignin-­‐relevant	
  dimers	
  have	
  also	
  shown	
  promising	
  results	
  for	
  the	
  ability	
  
of	
   ECH	
   to	
   cleave	
   lignin-­‐derived	
   linkages	
   that	
   could	
   be	
   present	
   in	
   bio-­‐oil.	
   Dabo	
   et	
   al.	
   used	
  
several	
  transition	
  metal	
  powders	
  embedded	
  in	
  reticulated	
  vitreous	
  carbon	
  (RVC)	
  to	
  study	
  
their	
  effects	
  on	
  4-­‐O-­‐5	
  linked	
  lignin	
  dimer	
  4-­‐phenoxyphenol.	
  In	
  these	
  studies	
  they	
  were	
  able	
  
to	
   show	
   the	
   conversion	
   of	
   4-­‐phenoxyphenol	
   to	
   phenol	
   and	
   traces	
   of	
   cyclohexanone	
   and	
  
cyclohexanol.69	
   As	
   a	
   fuel	
   intermediate,	
   cyclohexanol	
   is	
   preferred,	
   but	
   phenol	
   is	
   also	
   a	
  
desirable	
   product	
   and	
   the	
   ability	
   to	
   selectively	
   choose	
   between	
   cyclohexanol	
   and	
   phenol	
  
from	
   lignin	
   dimers	
   would	
   be	
   valuable.	
   In	
   addition,	
   the	
   study	
   of	
   water	
   soluble	
   fractions	
   of	
  
bio-­‐oil	
   by	
   Li	
   et	
   al.	
   indicate	
   partial	
   stabilization	
   achieved	
   through	
   ECH.	
   In	
   addition	
   to	
  
improving	
   storage	
   properties	
   of	
   bio-­‐oil	
   by	
   preventing	
   some	
   components	
   from	
  
polymerization,	
  it	
  was	
  observed	
  that	
  the	
  electrocatalytically	
  treated	
  bio-­‐oil	
  did	
  not	
  exhibit	
  
formation	
  of	
  precipitates	
  and	
  value	
  added	
  products	
  such	
  as	
  propylene	
  glycol	
  and	
  ethylene	
  
glycol	
   were	
   observed.	
   70	
   ECH	
   of	
   bio-­‐oil	
   could	
   have	
   great	
   potential	
   as	
   a	
   bio-­‐oil	
   upgrading	
  
scheme	
  and	
  further	
  work	
  in	
  this	
  area	
  should	
  include	
  electrocatalysis	
  of	
  whole	
  bio-­‐oil.	
  
	
  
	
  
	
  
	
  

20	
  
	
  

	
  
Table	
  1.3:	
  Electrocatalytic	
  reduction	
  of	
  various	
  substrates	
  using	
  different	
  catalysts	
  
Reference	
  
Substrate	
  
Catalyst	
  
Conditions	
  
Amouzegar	
  et	
  al.	
  71,	
  72,	
  73	
   Phenol	
  

Pt	
  

	
  

Quiroz	
  et	
  al.	
  74	
  

m-­‐xylene	
  

Pt/Pt	
  

	
  

Lamy-­‐Pitara	
  et	
  al.75	
  

Maleic	
  acid	
  

Pt/Pt	
  

	
  

Ilikti	
  et	
  al.	
  63	
  

Phenol	
  

Raney	
  Ni	
  

30°C,	
  pH	
  9	
  

Holt	
  et	
  al.	
  76	
  

2-­‐cyclohexene-­‐1-­‐one	
  

WS2	
  on	
  RVC	
  

Sulfur	
  

Dalavoy	
  et	
  al.	
  59	
  

Lactic	
  acid	
  

Ru/C	
  (Ru/RVC)	
  

70°C,	
  1atm	
  

Santana	
  et	
  al.	
  67,	
  77	
  

Various	
  organic	
  compounds	
  

Ni	
  on	
  Fe	
  

	
  

Li	
  et	
  al.	
  68	
  

Guaiacol,	
  phenol,	
  syringol	
  

Ru/ACC	
  

25-­‐80°C,	
  
1atm	
  
Robin	
  et	
  al.	
  60	
  

Polycyclic	
  aromatics	
  

Mahdavi	
  et	
  al.64	
  

Conjugated	
  enones	
  

Raney	
  Ni	
  
Ni2B,	
  Ni,	
  Raney	
  

80°C	
  
	
  

Ni	
  
Mahdavi	
  et	
  al.	
  62	
  

Lignin	
  model	
  dimers	
  	
  

Cyr	
  et	
  al.	
  61	
  

Lignin	
  model	
  dimers	
  	
  

Raney	
  Ni	
  	
  
Raney	
  Ni,	
  

	
  
25-­‐75°C	
  

Pd/RVC	
  
Ni,	
  Ni2B,	
  Raney	
  
Dabo	
  et	
  al.	
  69	
  

4-­‐phenoxyphenol	
  

Ni,	
  Pd/C,	
  Ru/C,	
  

	
  

Rh/C,	
  Pd/Al2O3,	
  
Rh/Al2O3,	
  Pd/Ni	
  
Li	
  et	
  al.	
  70	
  

Water	
  soluble	
  bio-­‐oil	
  

	
  

21	
  
	
  

Ru/Acc	
  

	
  

	
  
Conclusion	
  
Moving	
   away	
   from	
   fossil	
   fuels	
   and	
   displacing	
   them	
   with	
   alternative	
   sources	
  
becomes	
  more	
  and	
  more	
  relevant	
  due	
  to	
  the	
  connection	
  of	
  fossil	
  fuel	
  use	
  to	
  global	
  climate	
  
change	
   and	
   energy	
   crises.	
   Consequently,	
   energy	
   derived	
   from	
   biomass	
   has	
   become	
   an	
  
attractive	
   alternative	
   and	
   could	
   be	
   an	
   essential	
   part	
   of	
   future	
   energy	
   production.	
   However,	
  
effective	
   conversion	
   processes	
   are	
   needed	
   to	
   produce	
   liquid	
   fuels	
   and	
   value-­‐added	
  
commodities	
  from	
  biomass.	
  	
  Biomass	
  fast	
  pyrolysis,	
  coupled	
  with	
  upgrading	
  processes	
  such	
  
as	
   electrocatalytic	
   hydrogenation,	
   offers	
   a	
   promising	
   strategy	
   for	
   the	
   future	
   of	
   bioenergy	
  
production.	
   Even	
   though	
   human	
   beings	
   are	
   better	
   at	
   capturing	
   energy	
   in	
   the	
   form	
   of	
  
electricity,	
   plants	
   are	
   better	
   at	
   capturing	
   carbon	
   so	
   strategies	
   such	
   as	
   electrocatalytic	
  
hydrogenation	
   offer	
   the	
   opportunity	
   to	
   couple	
   carbon	
   free	
   energy	
   to	
   upgrade	
   biomass	
  
carbon	
  to	
  insure	
  a	
  more	
  complete	
  utilization	
  of	
  the	
  carbon	
  that	
  is	
  derived	
  from	
  biomass	
  vs.	
  
just	
   utilizing	
   the	
   energy	
   available	
   from	
   biomass.	
   Efforts	
   to	
   valorize	
   components	
   of	
   biomass	
  
such	
   as	
   lignin	
   offer	
   a	
   significant	
   advantage	
   as	
   lignin	
   is	
   one	
   of	
   the	
   majors	
   source	
   of	
   phenolic	
  
compounds	
   in	
   nature	
   that	
   have	
   the	
   potential	
   to	
   provide	
   liquid	
   fuels	
   and	
   value	
   added	
  
products	
  thus	
  providing	
  a	
  way	
  to	
  make	
  use	
  of	
  the	
  carbon	
  that	
  is	
  available.	
  	
  
Up	
   to	
   this	
   point	
   this	
   review	
   has	
   outlined	
   the	
   looming	
   environmental	
   and	
   energy	
  
related	
   impacts	
   of	
   burning	
   fossil	
   fuels	
   and	
   the	
   potential	
   of	
   biomass	
   components	
   such	
   as	
  
lignin	
   to	
   help	
   alleviate	
   some	
   of	
   these	
   issues.	
   Additionally	
   a	
   brief	
   review	
   of	
   pretreatment	
  
processes	
   as	
   a	
   way	
   of	
   enhancing	
   biomass	
   depolymerization	
   and	
   extraction	
   of	
   biomass	
  
components	
   and	
   the	
   use	
   of	
   fast	
   pyrolysis	
   as	
   a	
   conversion	
   method	
   were	
   covered.	
   Several	
  
challenges	
  that	
  prevent	
  fast	
  pyrolysis	
  products	
  such	
  as	
  bio-­‐oil	
  from	
  being	
  used	
  as	
  a	
  drop-­‐in	
  
fuel	
   were	
   mentioned	
   along	
   with	
   the	
   potential	
   use	
   of	
   electrocatalytic	
   hydrogenation	
   for	
  
22	
  
	
  

	
  
further	
   upgrading.	
   The	
   proceeding	
   chapters	
   will	
   cover	
   electrocatalytic	
   hydrogenation	
   of	
  
lignin-­‐derived	
   monomers	
   and	
   dimers	
   and	
   characterization	
   of	
   ammonia	
   extracted	
   lignin	
   for	
  
future	
  use	
  as	
  a	
  feed	
  material	
  for	
  bio-­‐oil	
  production.	
  	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

23	
  
	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
REFERENCES	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

24	
  
	
  

	
  
REFERENCES	
  
	
  
1.	
  

Stocker,	
  T.	
  F.,	
  D.	
  Qin,	
  G.-­‐K.	
  Plattner,	
  M.	
  Tignor,	
  S.K.	
  Allen,	
  J.	
  Boschung,	
  A.	
  Nauels,	
  Y.	
  
Xia,	
  V.	
  Bex	
  and	
  P.M.	
  Midgley,	
  IPCC,	
  2013:Climate	
  	
  Change	
  2013:	
  The	
  Physical	
  Science	
  
Basis.	
  Contribution	
  of	
  Working	
  Group	
  I	
  	
  to	
  the	
  Fifth	
  Assessment	
  Report	
  of	
  the	
  
Intergovernmental	
  Panel	
  on	
  Climate	
  Change[(eds.)].	
  .	
  Cambridge	
  University	
  Press,	
  
Cambridge,	
  United	
  Kingdom	
  and	
  New	
  York,	
  NY,	
  USA,	
  1535	
  pp:	
  2013.	
  

2.	
  

How	
  dependent	
  are	
  we	
  on	
  foreign	
  oil?	
  
http://www.eia.gov/energy_in_brief/article/foreign_oil_dependence.cfm.	
  Us	
  Energy	
  
Information	
  Administration.:	
  2013.	
  

3.	
  

Congress,	
  Energy	
  Independence	
  and	
  Security	
  Act	
  of	
  2007.”	
  	
  www.GovTrack.us.	
  
2007.	
  	
  	
  February	
  11,	
  2014<http://www.govtrack.us/congress/bills/110/hr6>.	
  
110th	
  ed.;	
  2007.	
  

4.	
  

Mohan,	
  D.;	
  Pittman,	
  C.	
  U.;	
  Steele,	
  P.	
  H.,	
  Pyrolysis	
  of	
  Wood/Biomass	
  for	
  Bio-­‐oil:  	
  A	
  
Critical	
  Review.	
  Energy	
  &	
  Fuels	
  2006,	
  20	
  (3),	
  848-­‐889.	
  

5.	
  

U.S.	
  Billion-­Ton	
  Update:	
  Biomass	
  Supply	
  for	
  a	
  Bioenergy	
  and	
  Bioproducts	
  Industry.;	
  
Oak	
  Ridge	
  National	
  Laboratory:	
  Oak	
  Ridge,	
  TN.,	
  2011;	
  p	
  227p.	
  

6.	
  

Renewable	
  Energy	
  Road	
  Map.	
  Renewable	
  energies	
  in	
  the	
  21st	
  century:	
  building	
  a	
  
more	
  sustainable	
  future.	
  
http://europa.eu/legislation_summaries/energy/renewable_energy/l27065_en.htm
.	
  2007.	
  

7.	
  

Lu,	
  Q.;	
  Li,	
  W.-­‐Z.;	
  Zhu,	
  X.-­‐F.,	
  Overview	
  of	
  fuel	
  properties	
  of	
  biomass	
  fast	
  pyrolysis	
  oils.	
  
Energy	
  Conversion	
  and	
  Management	
  2009,	
  50	
  (5),	
  1376-­‐1383.	
  

8.	
  

Bridgwater,	
  A.	
  V.;	
  Meier,	
  D.;	
  Radlein,	
  D.,	
  An	
  overview	
  of	
  fast	
  pyrolysis	
  of	
  biomass.	
  
Organic	
  Geochemistry	
  1999,	
  30	
  (12),	
  1479-­‐1493.	
  

9.	
  

Mason,	
  J.	
  E.,	
  World	
  energy	
  analysis:	
  H2	
  now	
  or	
  later?	
  Energy	
  Policy	
  2007,	
  35	
  (2),	
  
1315-­‐1329.	
  

10.	
  

Shafiee,	
  S.;	
  Topal,	
  E.,	
  An	
  econometrics	
  view	
  of	
  worldwide	
  fossil	
  fuel	
  consumption	
  
and	
  the	
  role	
  of	
  US.	
  Energy	
  Policy	
  2008,	
  36	
  (2),	
  775-­‐786.	
  

11.	
  

International	
  Energy	
  Outlook;	
  U.S.	
  Energy	
  Information	
  Administration.	
  
http://www.eia.gov/forecasts/ieo/index.cfm:	
  2013.	
  

12.	
  

Shafiee,	
  S.;	
  Topal,	
  E.,	
  When	
  will	
  fossil	
  fuel	
  reserves	
  be	
  diminished?	
  Energy	
  Policy	
  
2009,	
  37	
  (1),	
  181-­‐189.	
  

25	
  
	
  

	
  
13.	
  

Höök,	
  M.;	
  Tang,	
  X.,	
  Depletion	
  of	
  fossil	
  fuels	
  and	
  anthropogenic	
  climate	
  change—A	
  
review.	
  Energy	
  Policy	
  2013,	
  52	
  (0),	
  797-­‐809.	
  

14.	
  

Zecca,	
  A.;	
  Chiari,	
  L.,	
  Fossil-­‐fuel	
  constraints	
  on	
  global	
  warming.	
  Energy	
  Policy	
  2010,	
  
38	
  (1),	
  1-­‐3.	
  

15.	
  

National	
  Oceanic	
  and	
  Atmospheric	
  Administration.	
  CarbonTracker	
  CT2013,	
  
http://carbontracker.noaa.gov.	
  http://www.esrl.noaa.gov/gmd/cc,gg/trends/.	
  

16.	
  

Stocker,	
  T.	
  F.,	
  D.	
  Qin,	
  G.-­‐K.	
  Plattner,	
  M.	
  Tignor,	
  S.K.	
  Allen,	
  J.	
  Boschung,	
  A.	
  Nauels,	
  Y.	
  
Xia,	
  V.	
  Bex	
  and	
  P.M.	
  Midgley	
  (eds.)	
  IPCC,	
  2013:	
  Summary	
  for	
  Policymakers.	
  In:	
  Climate	
  
Change	
  2013:	
  The	
  Physical	
  Science	
  Basis.	
  Contribution	
  of	
  	
  Working	
  Group	
  I	
  to	
  the	
  Fifth	
  
Assessment	
  Report	
  of	
  the	
  Intergovernmental	
  	
  Panel	
  on	
  Climate	
  Change;	
  Cambridge,	
  
United	
  Kingdom	
  and	
  New	
  York,	
  NY,	
  USA.,	
  2013.	
  

17.	
  

Chiari,	
  L.;	
  Zecca,	
  A.,	
  Constraints	
  of	
  fossil	
  fuels	
  depletion	
  on	
  global	
  warming	
  
projections.	
  Energy	
  Policy	
  2011,	
  39	
  (9),	
  5026-­‐5034.	
  

18.	
  

Climate	
  Impacts	
  on	
  Society.	
  United	
  States	
  Environmental	
  Protection	
  Agency.	
  
http://www.epa.gov/climatechange/impacts-­‐adaptation/society.html.	
  

19.	
  

Thomas	
  R.	
  Karl,	
  J.	
  M.	
  M.,	
  and	
  Thomas	
  C.	
  Peterson,	
  Global	
  Climate	
  Change	
  Impacts	
  in	
  
the	
  United	
  States;	
  New	
  York,	
  NY,	
  USA,	
  2009.	
  

20.	
  

Bennett,	
  T.	
  M.	
  B.,	
  N.	
  G.	
  Maynard,	
  P.	
  Cochran,	
  R.	
  Gough,	
  K.	
  Lynn,	
  J.	
  Maldonado,	
  G.	
  
Voggesser,	
  S.	
  Wotkyns,	
  and	
  K.	
  Cozzetto	
  Ch.	
  12:	
  Indigenous	
  Peoples,	
  Lands,	
  and	
  
Resources.	
  Climate	
  Change	
  Impacts	
  	
  in	
  the	
  United	
  States:	
  The	
  Third	
  National	
  Climate	
  
Assessment,;	
  U.S.	
  Global	
  Change	
  Research	
  Program:	
  2014;	
  pp	
  297-­‐317.	
  

21.	
  

Climate	
  Change	
  and	
  Health.	
  World	
  Health	
  Organization.	
  
http://www.who.int/mediacentre/factsheets/fs266/en/.	
  

22.	
  

McKendry,	
  P.,	
  Energy	
  production	
  from	
  biomass	
  (part	
  1):	
  overview	
  of	
  biomass.	
  
Bioresource	
  Technology	
  2002,	
  83	
  (1),	
  37-­‐46.	
  

23.	
  

Qu,	
  T.	
  T.;	
  Guo,	
  W.	
  J.;	
  Shen,	
  L.	
  H.;	
  Xiao,	
  J.;	
  Zhao,	
  K.,	
  Experimental	
  Study	
  of	
  Biomass	
  
Pyrolysis	
  Based	
  on	
  Three	
  Major	
  Components:	
  Hemicellulose,	
  Cellulose,	
  and	
  Lignin.	
  
Industrial	
  &	
  Engineering	
  Chemistry	
  Research	
  2011,	
  50	
  (18),	
  10424-­‐10433.	
  

24.	
  

Yang,	
  H.;	
  Yan,	
  R.;	
  Chen,	
  H.;	
  Lee,	
  D.	
  H.;	
  Zheng,	
  C.,	
  Characteristics	
  of	
  hemicellulose,	
  
cellulose	
  and	
  lignin	
  pyrolysis.	
  Fuel	
  2007,	
  86	
  (12-­‐13),	
  1781-­‐1788.	
  

25.	
  

Pandey,	
  M.	
  P.;	
  Kim,	
  C.	
  S.,	
  Lignin	
  Depolymerization	
  and	
  Conversion:	
  A	
  Review	
  of	
  
Thermochemical	
  Methods.	
  Chemical	
  Engineering	
  &	
  Technology	
  2011,	
  34	
  (1),	
  29-­‐41.	
  

26.	
  

Pandey,	
  M.	
  P.	
  a.	
  K.,	
  C.	
  S.	
  	
  Chem.	
  Eng.	
  Technol.,	
  	
  34:	
  29–41.	
  doi:	
  
10.1002/ceat.201000270,	
  Lignin	
  Depolymerization	
  and	
  	
  Conversion:	
  A	
  Review	
  of	
  
26	
  
	
  

	
  
Thermochemical	
  Methods.	
  Chem.	
  Eng.	
  Technol.:	
  2011;	
  Vol.	
  34:	
  29–41.	
  
doi:	
  10.1002/ceat.201000270.	
  
27.	
  

Zakzeski,	
  J.;	
  Bruijnincx,	
  P.	
  C.	
  A.;	
  Jongerius,	
  A.	
  L.;	
  Weckhuysen,	
  B.	
  M.,	
  The	
  Catalytic	
  
Valorization	
  of	
  Lignin	
  for	
  the	
  Production	
  of	
  Renewable	
  Chemicals.	
  Chemical	
  Reviews	
  
2010,	
  110	
  (6),	
  3552-­‐3599.	
  

28.	
  

Mahdavi,	
  B.;	
  Lafrance,	
  A.;	
  Martel,	
  A.;	
  Lessard,	
  J.;	
  Menard,	
  H.;	
  Brossard,	
  L.,	
  
Electrocatalytic	
  hydrogenolysis	
  of	
  lignin	
  model	
  dimers	
  at	
  Raney	
  nickel	
  electrodes.	
  J.	
  
Appl.	
  Electrochem.	
  1997,	
  27	
  (5),	
  605-­‐611.	
  

29.	
  

Patwardhan,	
  P.	
  R.;	
  Brown,	
  R.	
  C.;	
  Shanks,	
  B.	
  H.,	
  Understanding	
  the	
  Fast	
  Pyrolysis	
  of	
  
Lignin.	
  ChemSusChem	
  2011,	
  4	
  (11),	
  1629-­‐1636.	
  

30.	
  

Vanholme,	
  R.;	
  Demedts,	
  B.;	
  Morreel,	
  K.;	
  Ralph,	
  J.;	
  Boerjan,	
  W.,	
  Lignin	
  Biosynthesis	
  
and	
  Structure.	
  Plant	
  Physiology	
  2010,	
  153	
  (3),	
  895-­‐905.	
  

31.	
  

Lu,	
  F.;	
  Ralph,	
  J.;	
  Sun,	
  R.-­‐C.,	
  Chapter	
  6	
  -­‐	
  Lignin.	
  In	
  Cereal	
  Straw	
  as	
  a	
  Resource	
  for	
  
Sustainable	
  Biomaterials	
  and	
  Biofuels,	
  Elsevier:	
  Amsterdam,	
  2010;	
  pp	
  169-­‐207.	
  

32.	
  

Saiz-­‐Jimenez,	
  C.;	
  De	
  Leeuw,	
  J.	
  W.,	
  Lignin	
  pyrolysis	
  products:	
  Their	
  structures	
  and	
  
their	
  significance	
  as	
  biomarkers.	
  Organic	
  Geochemistry	
  1986,	
  10	
  (4–6),	
  869-­‐876.	
  

33.	
  

Amen-­‐Chen,	
  C.;	
  Pakdel,	
  H.;	
  Roy,	
  C.,	
  Production	
  of	
  monomeric	
  phenols	
  by	
  
thermochemical	
  conversion	
  of	
  biomass:	
  a	
  review.	
  Bioresour.	
  Technol.	
  2001,	
  79	
  (3),	
  
277-­‐299.	
  

34.	
  

Landucci,	
  L.	
  L.;	
  Luque,	
  S.;	
  Ralph,	
  S.,	
  Reaction	
  of	
  p-­‐Hydroxycinnamyl	
  Alcohols	
  with	
  
Transition	
  Metal	
  Salts.	
  2.	
  Preparation	
  of	
  Guaiacyl/Syringyl	
  Di-­‐,	
  Tri-­‐,	
  and	
  Tetralignols.	
  
Journal	
  of	
  Wood	
  Chemistry	
  and	
  Technology	
  1995,	
  15	
  (4),	
  493-­‐513.	
  

35.	
  

Chioccara,	
  F.;	
  Poli,	
  S.;	
  Rindone,	
  B.;	
  Pilati,	
  T.;	
  Brunow,	
  G.;	
  Pietikaeinen,	
  P.;	
  Setaelae,	
  H.,	
  
ChemInform	
  Abstract:	
  Regio-­‐	
  and	
  Diastereoselective	
  Synthesis	
  of	
  Dimeric	
  Lignans	
  
Using	
  Oxidative	
  Coupling.	
  ChemInform	
  1993,	
  24	
  (36).	
  

36.	
  

Ralph,	
  J.;	
  Lundquist,	
  K.;	
  Brunow,	
  G.;	
  Lu,	
  F.;	
  Kim,	
  H.;	
  Schatz,	
  P.;	
  Marita,	
  J.;	
  Hatfield,	
  R.;	
  
Ralph,	
  S.;	
  Christensen,	
  J.;	
  Boerjan,	
  W.,	
  Lignins:	
  Natural	
  polymers	
  from	
  oxidative	
  
coupling	
  of	
  4-­‐hydroxyphenyl-­‐	
  propanoids.	
  Phytochemistry	
  Reviews	
  2004,	
  3	
  (1-­‐2),	
  
29-­‐60.	
  

37.	
  

Derkacheva,	
  O.;	
  Sukhov,	
  D.,	
  Investigation	
  of	
  Lignins	
  by	
  FTIR	
  Spectroscopy.	
  
Macromolecular	
  Symposia	
  2008,	
  265	
  (1),	
  61-­‐68.	
  

38.	
  

Sun,	
  Y.;	
  Cheng,	
  J.,	
  Hydrolysis	
  of	
  lignocellulosic	
  materials	
  for	
  ethanol	
  production:	
  a	
  
review.	
  Bioresource	
  Technology	
  2002,	
  83	
  (1),	
  1-­‐11.	
  

27	
  
	
  

	
  
39.	
  

Galbe,	
  M.;	
  Zacchi,	
  G.,	
  Pretreatment	
  of	
  Lignocellulosic	
  Materials	
  for	
  Efficient	
  
Bioethanol	
  Production.	
  In	
  Biofuels,	
  Olsson,	
  L.,	
  Ed.	
  Springer	
  Berlin	
  Heidelberg:	
  2007;	
  
Vol.	
  108,	
  pp	
  41-­‐65.	
  

40.	
  

Yat,	
  S.	
  C.;	
  Berger,	
  A.;	
  Shonnard,	
  D.	
  R.,	
  Kinetic	
  characterization	
  for	
  dilute	
  sulfuric	
  acid	
  
hydrolysis	
  of	
  timber	
  varieties	
  and	
  switchgrass.	
  Bioresource	
  Technology	
  2008,	
  99	
  (9),	
  
3855-­‐3863.	
  

41.	
  

Keshwani,	
  D.	
  R.;	
  Cheng,	
  J.	
  J.,	
  Switchgrass	
  for	
  bioethanol	
  and	
  other	
  value-­‐added	
  
applications:	
  A	
  review.	
  Bioresource	
  Technology	
  2009,	
  100	
  (4),	
  1515-­‐1523.	
  

42.	
  

Schell,	
  D.;	
  Harwood,	
  C.,	
  Milling	
  of	
  lignocellulosic	
  biomass.	
  Applied	
  Biochemistry	
  and	
  
Biotechnology	
  1994,	
  45-­46	
  (1),	
  159-­‐168.	
  

43.	
  

Kumar,	
  P.;	
  Barrett,	
  D.	
  M.;	
  Delwiche,	
  M.	
  J.;	
  Stroeve,	
  P.,	
  Methods	
  for	
  Pretreatment	
  of	
  
Lignocellulosic	
  Biomass	
  for	
  Efficient	
  Hydrolysis	
  and	
  Biofuel	
  Production.	
  Industrial	
  &	
  
Engineering	
  Chemistry	
  Research	
  2009,	
  48	
  (8),	
  3713-­‐3729.	
  

44.	
  

Alvira,	
  P.;	
  Tomás-­‐Pejó,	
  E.;	
  Ballesteros,	
  M.;	
  Negro,	
  M.	
  J.,	
  Pretreatment	
  technologies	
  for	
  
an	
  efficient	
  bioethanol	
  production	
  process	
  based	
  on	
  enzymatic	
  hydrolysis:	
  A	
  review.	
  
Bioresource	
  Technology	
  2010,	
  101	
  (13),	
  4851-­‐4861.	
  

45.	
  

McMillan	
  James,	
  D.,	
  Pretreatment	
  of	
  Lignocellulosic	
  Biomass.	
  In	
  Enzymatic	
  
Conversion	
  of	
  Biomass	
  for	
  Fuels	
  Production,	
  American	
  Chemical	
  Society:	
  1994;	
  Vol.	
  
566,	
  pp	
  292-­‐324.	
  

46.	
  

Bals,	
  B.;	
  Rogers,	
  C.;	
  Jin,	
  M.;	
  Balan,	
  V.;	
  Dale,	
  B.,	
  Evaluation	
  of	
  ammonia	
  fibre	
  expansion	
  
(AFEX)	
  pretreatment	
  for	
  enzymatic	
  hydrolysis	
  of	
  switchgrass	
  harvested	
  in	
  different	
  
seasons	
  and	
  locations.	
  Biotechnology	
  for	
  Biofuels	
  C7	
  -­	
  1	
  2010,	
  3	
  (1),	
  1-­‐11.	
  

47.	
  

Dale,	
  B.	
  E.,	
  Biobased	
  Industrial	
  Products:	
  Bioprocess	
  Engineering	
  When	
  Cost	
  Really	
  
Counts.	
  Biotechnology	
  Progress	
  1999,	
  15	
  (5),	
  775-­‐776.	
  

48.	
  

Dale,	
  B.;	
  Weaver,	
  J.;	
  Byers,	
  F.	
  M.,	
  Extrusion	
  processing	
  for	
  ammonia	
  fiber	
  explosion	
  
(AFEX).	
  Applied	
  Biochemistry	
  and	
  Biotechnology	
  1999,	
  77	
  (1-­‐3),	
  35-­‐45.	
  

49.	
  

Moniruzzaman,	
  M.;	
  Dien,	
  B.;	
  Ferrer,	
  B.;	
  Hespell,	
  R.;	
  Dale,	
  B.;	
  Ingram,	
  L.;	
  Bothast,	
  R.,	
  
Ethanol	
  production	
  from	
  AFEX	
  pretreated	
  corn	
  fiber	
  by	
  recombinant	
  bacteria.	
  
Biotechnology	
  Letters	
  1996,	
  18	
  (8),	
  985-­‐990.	
  

50.	
  

McKendry,	
  P.,	
  Energy	
  production	
  from	
  biomass	
  (part	
  2):	
  conversion	
  technologies.	
  
Bioresource	
  Technology	
  2002,	
  83	
  (1),	
  47-­‐54.	
  

51.	
  

Meier,	
  D.;	
  Faix,	
  O.,	
  State	
  of	
  the	
  art	
  of	
  applied	
  fast	
  pyrolysis	
  of	
  lignocellulosic	
  
materials	
  —	
  a	
  review.	
  Bioresource	
  Technology	
  1999,	
  68	
  (1),	
  71-­‐77.	
  

28	
  
	
  

	
  
52.	
  

Czernik,	
  S.;	
  Bridgwater,	
  A.	
  V.,	
  Overview	
  of	
  Applications	
  of	
  Biomass	
  Fast	
  Pyrolysis	
  Oil.	
  
Energy	
  &	
  Fuels	
  2004,	
  18	
  (2),	
  590-­‐598.	
  

53.	
  

Diebold,	
  J.	
  P.,	
  A	
  Review	
  of	
  the	
  Chemical	
  and	
  Physical	
  Mechanisms	
  of	
  the	
  Storage	
  
Stability	
  of	
  Fast	
  Pyrolysis	
  Bio-­‐Oils.	
  Czernik,	
  N.	
  T.	
  M.	
  S.,	
  Ed.	
  2000.	
  

54.	
  

Rensel,	
  D.	
  J.;	
  Rouvimov,	
  S.;	
  Gin,	
  M.	
  E.;	
  Hicks,	
  J.	
  C.,	
  Highly	
  selective	
  bimetallic	
  FeMoP	
  
catalyst	
  for	
  C–O	
  bond	
  cleavage	
  of	
  aryl	
  ethers.	
  Journal	
  of	
  Catalysis	
  2013,	
  305	
  (0),	
  256-­‐
263.	
  

55.	
  

French,	
  R.;	
  Czernik,	
  S.,	
  Catalytic	
  pyrolysis	
  of	
  biomass	
  for	
  biofuels	
  production.	
  Fuel	
  
Processing	
  Technology	
  2010,	
  91	
  (1),	
  25-­‐32.	
  

56.	
  

Rothenberg,	
  G.,	
  Heterogeneous	
  Catalysis.	
  In	
  Catalysis,	
  Wiley-­‐VCH	
  Verlag	
  GmbH	
  &	
  Co.	
  
KGaA:	
  2008;	
  pp	
  127-­‐187.	
  

57.	
  

Bu,	
  Q.;	
  Lei,	
  H.;	
  Zacher,	
  A.	
  H.;	
  Wang,	
  L.;	
  Ren,	
  S.;	
  Liang,	
  J.;	
  Wei,	
  Y.;	
  Liu,	
  Y.;	
  Tang,	
  J.;	
  Zhang,	
  
Q.;	
  Ruan,	
  R.,	
  A	
  review	
  of	
  catalytic	
  hydrodeoxygenation	
  of	
  lignin-­‐derived	
  phenols	
  
from	
  biomass	
  pyrolysis.	
  Bioresource	
  Technology	
  2012,	
  124	
  (0),	
  470-­‐477.	
  

58.	
  

Dalavoy,	
  T.	
  S.;	
  Jackson,	
  J.	
  E.;	
  Swain,	
  G.	
  M.;	
  Miller,	
  D.	
  J.;	
  Li,	
  J.;	
  Lipkowski,	
  J.,	
  Mild	
  
electrocatalytic	
  hydrogenation	
  of	
  lactic	
  acid	
  to	
  lactaldehyde	
  and	
  propylene	
  glycol.	
  
Journal	
  of	
  Catalysis	
  2007,	
  246	
  (1),	
  15-­‐28.	
  

59.	
  

Robin,	
  D.;	
  Comtois,	
  M.;	
  Martel,	
  A.;	
  Lemieux,	
  R.;	
  Cheong,	
  A.	
  K.;	
  Belot,	
  G.;	
  Lessard,	
  J.,	
  The	
  
electrocatalytic	
  hydrogenation	
  of	
  fused	
  poly	
  cyclic	
  aromatic	
  compounds	
  at	
  Raney	
  
nickel	
  electrodes:	
  the	
  influence	
  of	
  catalyst	
  activation	
  and	
  electrolysis	
  conditions.	
  
Canadian	
  Journal	
  of	
  Chemistry	
  1990,	
  68	
  (7),	
  1218-­‐1227.	
  

60.	
  

Cyr,	
  A.;	
  Chiltz,	
  F.;	
  Jeanson,	
  P.;	
  Martel,	
  A.;	
  Brossard,	
  L.;	
  Lessard,	
  J.;	
  Menard,	
  H.,	
  
Electrocatalytic	
  hydrogenation	
  of	
  lignin	
  models	
  at	
  Raney	
  nickel	
  and	
  palladium-­‐
based	
  electrodes.	
  Can.	
  J.	
  Chem.-­Rev.	
  Can.	
  Chim.	
  2000,	
  78	
  (3),	
  307-­‐315.	
  

61.	
  

Mahdavi,	
  B.;	
  Lafrance,	
  A.;	
  Martel,	
  A.;	
  Lessard,	
  J.;	
  Me´Nard,	
  H.;	
  Brossard,	
  L.,	
  
Electrocatalytic	
  hydrogenolysis	
  of	
  lignin	
  model	
  dimers	
  at	
  Raney	
  nickel	
  electrodes.	
  
Journal	
  of	
  Applied	
  Electrochemistry	
  1997,	
  27	
  (5),	
  605-­‐611.	
  

62.	
  

Ilikti,	
  H.;	
  Rekik,	
  N.;	
  Thomalla,	
  M.,	
  Electrocatalytic	
  hydrogenation	
  of	
  phenol	
  in	
  
aqueous	
  solutions	
  at	
  a	
  Raney	
  nickel	
  electrode	
  in	
  the	
  presence	
  of	
  cationic	
  surfactants.	
  
Journal	
  of	
  Applied	
  Electrochemistry	
  2002,	
  32	
  (6),	
  603-­‐609.	
  

63.	
  

Mahdavi,	
  B.;	
  Chambrion,	
  P.;	
  Binette,	
  J.;	
  Martel,	
  E.;	
  Lessard,	
  J.,	
  Electrocatalytic	
  
Hydrogenation	
  of	
  Conjugated	
  Enones	
  on	
  Nickel	
  Boride,	
  Nickel,	
  and	
  Raney-­‐Nickel	
  
Electrodes.	
  Can.	
  J.	
  Chem.-­Rev.	
  Can.	
  Chim.	
  1995,	
  73	
  (6),	
  846-­‐852.	
  

29	
  
	
  

	
  
64.	
  

Antonietta	
  Casadei,	
  M.;	
  Pletcher,	
  D.,	
  The	
  influence	
  of	
  conditions	
  on	
  the	
  
electrocatalytic	
  hydrogenation	
  of	
  organic	
  molecules.	
  Electrochimica	
  Acta	
  1988,	
  33	
  
(1),	
  117-­‐120.	
  

65.	
  

Dalavoy,	
  T.	
  S.;	
  Jackson,	
  J.	
  E.;	
  Swain,	
  G.	
  M.;	
  Miller,	
  D.	
  J.,	
  Mild	
  electrocatalytic	
  
hydrogenation	
  of	
  alpha	
  functionalized	
  carboxylic	
  acids.	
  Abstracts	
  of	
  Papers	
  of	
  the	
  
American	
  Chemical	
  Society	
  2006,	
  231.	
  

66.	
  

Amouzegar,	
  K.;	
  Savadogo,	
  O.,	
  Electrocatalytic	
  hydrogenation	
  of	
  phenol	
  on	
  highly	
  
dispersed	
  Pt	
  electrodes.	
  Electrochimica	
  acta	
  1994,	
  39	
  (4),	
  557-­‐559.	
  

67.	
  

Amouzegar,	
  K.;	
  Savadogo,	
  O.,	
  Electrocatalytic	
  hydrogenation	
  of	
  phenol	
  on	
  dispersed	
  
Pt:	
  reaction	
  mechanism	
  and	
  support	
  effect.	
  Electrochimica	
  Acta	
  1997,	
  43	
  (5–6),	
  503-­‐
508.	
  

68.	
  

Amouzegar,	
  K.;	
  Savadogo,	
  O.,	
  Electrocatalytic	
  hydrogenation	
  of	
  phenol	
  on	
  dispersed	
  
Pt:	
  Effect	
  of	
  metal	
  electrochemically	
  active	
  surface	
  area	
  and	
  electrode	
  material.	
  J.	
  
Appl.	
  Electrochem.	
  1997,	
  27	
  (5),	
  539-­‐542.	
  

69.	
  

Quiroz,	
  M.	
  A.;	
  Córdova,	
  F.;	
  Lamy-­‐Pitara,	
  E.;	
  Barbier,	
  J.,	
  Electrocatalytic	
  hydrogenation	
  
of	
  m-­‐xylene	
  on	
  platinized-­‐platinum	
  electrodes.	
  Electrochimica	
  Acta	
  2000,	
  45	
  (25–
26),	
  4291-­‐4298.	
  

70.	
  

Lamy-­‐Pitara,	
  E.;	
  El	
  Mouahid,	
  S.;	
  Barbier,	
  J.,	
  Effect	
  of	
  anions	
  on	
  catalytic	
  and	
  
electrocatalytic	
  hydrogenations	
  and	
  on	
  the	
  electrocatalytic	
  oxidation	
  and	
  evolution	
  
of	
  hydrogen	
  on	
  platinum.	
  Electrochimica	
  Acta	
  2000,	
  45	
  (25–26),	
  4299-­‐4308.	
  

71.	
  

Holt,	
  C.	
  M.	
  B.;	
  Murphy,	
  S.;	
  Gray,	
  M.	
  R.;	
  Mitlin,	
  D.,	
  Electrocatalytic	
  hydrogenation	
  of	
  2-­‐
cyclohexen-­‐1-­‐one	
  in	
  a	
  high	
  sulfur	
  environment	
  using	
  a	
  carbon-­‐supported	
  
nanostructured	
  tungsten	
  sulfide	
  catalyst.	
  Catalysis	
  Communications	
  2010,	
  12	
  (4),	
  
314-­‐317.	
  

72.	
  

Santana,	
  D.	
  S.;	
  Melo,	
  G.	
  O.;	
  Lima,	
  M.	
  V.	
  F.;	
  Daniel,	
  J.	
  R.	
  R.;	
  Areias,	
  M.	
  C.	
  C.;	
  Navarro,	
  M.,	
  
Electrocatalytic	
  hydrogenation	
  of	
  organic	
  compounds	
  using	
  a	
  nickel	
  sacrificial	
  
anode.	
  Journal	
  of	
  Electroanalytical	
  Chemistry	
  2004,	
  569	
  (1),	
  71-­‐78.	
  

73.	
  

Santana,	
  D.	
  S.;	
  Lima,	
  M.	
  V.	
  F.;	
  Daniel,	
  J.	
  R.	
  R.;	
  Navarro,	
  M.,	
  Electrocatalytic	
  
hydrogenation	
  of	
  organic	
  compounds	
  using	
  current	
  density	
  gradient	
  and	
  sacrificial	
  
anode	
  of	
  nickel.	
  Tetrahedron	
  Letters	
  2003,	
  44	
  (25),	
  4725-­‐4727.	
  

74.	
  

Li,	
  Z.;	
  Garedew,	
  M.;	
  Lam,	
  C.	
  H.;	
  Jackson,	
  J.	
  E.;	
  Miller,	
  D.	
  J.;	
  Saffron,	
  C.	
  M.,	
  Mild	
  
electrocatalytic	
  hydrogenation	
  and	
  hydrodeoxygenation	
  of	
  bio-­‐oil	
  derived	
  phenolic	
  
compounds	
  using	
  ruthenium	
  supported	
  on	
  activated	
  carbon	
  cloth.	
  Green	
  Chemistry	
  
2012,	
  14	
  (9),	
  2540-­‐2549.	
  

75.	
  

Dabo,	
  P.;	
  Cyr,	
  A.;	
  Lessard,	
  J.;	
  Brossard,	
  L.;	
  Ménard,	
  H.,	
  Electrocatalytic	
  hydrogenation	
  
of	
  4-­‐phenoxyphenol	
  on	
  active	
  powders	
  highly	
  dispersed	
  in	
  a	
  reticulated	
  vitreous	
  
30	
  
	
  

	
  
carbon	
  electrode.	
  Canadian	
  Journal	
  of	
  Chemistry-­revue	
  Canadienne	
  De	
  Chimie	
  1999,	
  
77	
  (7),	
  1225-­‐1229.	
  
76.	
  

Li,	
  Z.;	
  Kelkar,	
  S.;	
  Raycraft,	
  L.;	
  Garedew,	
  M.;	
  Jackson,	
  J.	
  E.;	
  Miller,	
  D.	
  J.;	
  Saffron,	
  C.	
  M.,	
  A	
  
mild	
  approach	
  for	
  bio-­‐oil	
  stabilization	
  and	
  upgrading:	
  electrocatalytic	
  
hydrogenation	
  using	
  ruthenium	
  supported	
  on	
  activated	
  carbon	
  cloth.	
  Green	
  
Chemistry	
  2014,	
  16	
  (2),	
  844-­‐852.	
  

31	
  
	
  

	
  
Chapter	
  2	
  : Electrocatalytic	
  Hydrogenation	
  and	
  Deoxygenation	
  of	
  Lignin	
  Model	
  
Compounds	
  using	
  Ruthenium	
  Supported	
  on	
  Activated	
  Carbon	
  Cloth	
  	
  	
  
Abstract	
  
	
  

Carbon	
   and	
   energy	
   efficient	
   strategies	
   are	
   needed	
   to	
   produce	
   hydrocarbon	
   fuels	
  

from	
   biomass.	
   	
   Fast	
   pyrolysis	
   provides	
   one	
   method	
   for	
   making	
   hydrocarbon	
   fuels	
   from	
  
biomass	
  or	
  components	
  of	
  biomass	
  such	
  as	
  lignin	
  in	
  an	
  efficient	
  manner.	
  	
  	
  Bio-­‐oil,	
  the	
  liquid	
  
product	
  of	
  fast	
  pyrolysis,	
  has	
  increased	
  bulk	
  density	
  when	
  compared	
  to	
  biomass	
  and	
  is	
  less	
  
expensive	
  to	
  transport	
  long	
  distances.	
  However,	
  bio-­‐oil	
  properties	
  include	
  self-­‐reactivity	
  to	
  
form	
   viscous	
   sludge	
   and	
   reactivity	
   with	
   metal	
   surfaces	
   causing	
   corrosion.	
   The	
   partial	
  
upgrading	
   (stabilization)	
   of	
   bio-­‐oil	
   using	
   electrocatalysis,	
   an	
   approach	
   where	
   electricity	
  
serves	
   as	
   the	
   reducing	
   agent,	
   is	
   proposed	
   to	
   improve	
   bio-­‐oil’s	
   properties.	
   	
   This	
   study	
  
focuses	
   on	
   the	
   electrocatalytic	
   hydrogenation	
   (ECH)	
   of	
   lignin	
   derived	
   bio-­‐oil	
   products	
   such	
  
as	
  alkoxyphenols	
  as	
  well	
  as	
  the	
  potential	
  of	
  this	
  process	
  for	
  cleaving	
  lignin	
  dimer	
  linkages.	
  
Ruthenium	
  supported	
  on	
  activated	
  carbon	
  cloth	
  (Ru/ACC)	
  is	
  used	
  as	
  the	
  catalytic	
  cathode	
  
under	
  mild	
  conditions	
  (80	
  °C	
  and	
  1atm).	
  	
  While	
  studying	
  the	
  ECH	
  of	
  methoxyphenols	
  with	
  
the	
   methoxy	
   groups	
   at	
   different	
   positions	
   in	
   the	
   ring,	
   the	
   reduction	
   of	
   the	
   methoxyphenols	
  
to	
   methoxycyclohexanol	
   and	
   cyclohexanol	
   was	
   demonstrated.	
   	
   Furthermore,	
   Ru/ACC	
   was	
  
found	
  to	
  be	
  capable	
  of	
  cleaving	
  and	
  reducing	
  lignin-­‐derived	
  dimers.	
  
Introduction	
  	
  
Due	
   to	
   the	
   increasing	
   problem	
   of	
   depleting	
   fossil	
   fuels	
   and	
   growing	
   environmental	
  
concerns,	
   interest	
   in	
   alternative	
   energy	
   sources	
   has	
   increased	
   substantially.	
   The	
  
development	
  of	
  alternative	
  energy	
  production	
  methods	
  that	
  are	
  environmentally	
  friendly,	
  

32	
  
	
  

	
  
economically	
   sound	
   and	
   that	
   do	
   not	
   compete	
   with	
   global	
   food	
   supply	
   is	
   essential.	
   To	
   this	
  
end,	
  production	
  of	
  fuels	
  from	
  biomass	
  has	
  been	
  gaining	
  attention	
  in	
  recent	
  years.	
  	
  As	
  plants	
  
store	
   energy	
   from	
   the	
   sun	
   in	
   the	
   form	
   of	
   chemical	
   bonds,	
   biomass	
   has	
   great	
   potential	
   to	
  
make	
  a	
  significant	
  contribution	
  to	
  alternative	
  sources	
  of	
  energy.1	
  Biomass	
  is	
  composed	
  of	
  
three	
   major	
   components:	
   cellulose,	
   hemicellulose	
   and	
   lignin.	
   	
   Cellulose	
   is	
   a	
   polymer	
   of	
  
glucose	
   arranged	
   either	
   in	
   a	
   crystalline	
   or	
   amorphous	
   form.2	
   Hemicellulose	
   is	
   an	
  
amorphous,	
   branched	
   polymer	
   of	
   pentoses	
   and	
   hexoses.2	
   Lignin	
   is	
   a	
   highly	
   complex	
  
polymer	
   made	
   via	
   the	
   polymerization	
   of	
   three	
   monolignols	
   joined	
   together	
   with	
   carbon-­‐
oxygen	
  bonds	
  at	
  the	
  α	
  and/or	
  β	
  positions	
  of	
  a	
  phenyl	
  ring	
  to	
  form	
  a	
  branched	
  network.2-­‐4	
  
Lignin	
  acts	
  as	
  a	
  binding	
  agent	
  filling	
  up	
  the	
  empty	
  space	
  in	
  plant	
  cell	
  walls.5	
  Depending	
  on	
  
the	
   type	
   of	
   biomass,	
   hemicellulose	
   accounts	
   for	
   about	
   20-­‐40	
   wt%,	
   cellulose	
   about	
   35-­‐60	
  
wt%	
  and	
  lignin	
  accounts	
  for	
  about	
  10-­‐25	
  wt%	
   and	
   40%	
   of	
   the	
   energy	
   content	
   of	
  biomass.6	
  
Deconstructing	
   different	
   components	
   of	
   biomass	
   in	
   an	
   efficient	
   manner	
   will	
   help	
   in	
   the	
  
production	
  of	
  biomass-­‐based	
  liquid	
  fuels	
  and	
  further	
  help	
  displace	
  petroleum.	
  	
  	
  
Cellulose	
  and	
  hemicellulose	
  have	
  been	
  well	
  studied	
  for	
  conversion	
  into	
  fuel	
  ethanol	
  as	
  
they	
  are	
  made	
  of	
  simple	
  sugars.	
  	
  Although	
  lignin	
  is	
  an	
  attractive	
  feed	
  for	
  the	
  production	
  of	
  
hydrocarbon	
   fuels	
   due	
   to	
   its	
   lower	
   O:C	
   ratio	
   compared	
   to	
   cellulose	
   and	
   hemicellulose,	
  
because	
  of	
  its	
  complex	
  structure,	
  lignin	
  has	
  been	
  one	
  of	
  the	
  more	
  difficult	
  components	
  to	
  
deconstruct	
  and	
  use	
  as	
  fuel.7	
  Often	
  a	
  byproduct	
  of	
  ethanol	
  and	
  pulp	
  and	
  paper	
  industries,	
  
lignin	
  is	
  burned	
  for	
  heat	
  or	
  discarded	
  as	
  a	
  waste	
  product.3	
  For	
  instance,	
  only	
  2%	
  (about	
  one	
  
million	
  tonnes)	
  of	
  the	
  lignin	
  produced	
  as	
  the	
  byproduct	
  of	
  the	
  pulp	
  and	
  paper	
  industry	
  is	
  in	
  
commercial	
   use.8	
   Unraveling	
   this	
   complex	
   polymer	
   and	
   being	
   able	
   to	
   produce	
   valuable	
  
monomeric	
   phenols	
   is	
   of	
   great	
   interest.9	
   To	
   this	
   end,	
   lignin	
   extraction,	
   cleaving	
   of	
   α	
   aryl	
  
33	
  
	
  

	
  
and	
  β	
  aryl	
  ethers	
  (depolymerization)	
  and	
  conversion	
  offers	
  an	
  alternative	
  method	
  for	
  the	
  
production	
  of	
  energy	
  efficient	
  liquid	
  fuel	
  as	
  well	
  as	
  value	
  added	
  products.	
  	
  
Extractive	
  ammonia	
  processing	
  (EAP)	
  is	
  a	
  pretreatment	
  method	
  that	
  is	
  used	
  to	
  separate	
  
lignin	
   from	
   cellulose	
   and	
   hemicellulose.10	
   During	
   EAP,	
   ammonia	
   is	
   added	
   to	
   biomass	
   at	
  
moderate	
   pressure	
   and	
   temperature.	
   	
   The	
   pressure	
   is	
   then	
   rapidly	
   released	
   to	
   cause	
   the	
  
fibers	
   to	
   expand.	
   This	
   process	
   results	
   in	
   cellulose	
   decrystallization,	
   hemicellulose	
  
hydrolysis,	
  and	
  partial	
  lignin	
  depolymerization.10	
  The	
  cellulose	
  and	
  hemicellulose	
  can	
  then	
  
be	
   subjected	
   to	
   enzymatic	
   hydrolysis	
   for	
   ethanol	
   production	
   while	
   lignin	
   streams	
   are	
  
collected,	
  fractionated	
  and	
  extracted.	
  	
  These	
  lignin	
  streams	
  are	
  partially	
  depolymerized	
  and	
  
are	
  thus	
  lower	
  in	
  molecular	
  weight	
  than	
  the	
  native	
  lignin	
  complex	
  found	
  in	
  biomass.	
  Lignin	
  
monomers	
   and	
   oligomers	
   are	
   more	
   amenable	
   to	
   chemical	
   transformation	
   to	
   higher	
   value	
  
fuels	
  and	
  chemicals	
  and	
  are	
  thus	
  better	
  feedstocks	
  than	
  native	
  lignin.	
  	
  	
  	
  
Thermochemical	
  conversion	
  processes	
  such	
  as	
  biomass	
  fast	
  pyrolysis	
  can	
  be	
  applied	
  for	
  
further	
   such	
   depolymerization.	
   Biomass	
   fast	
   pyrolysis	
   (BFP)	
   is	
   one	
   of	
   the	
   processes	
   used	
  
for	
  the	
  production	
  of	
  liquid	
  bio-­‐fuels	
  from	
  plant	
  matter	
  due	
  to	
  its	
  potential	
  for	
  producing	
  
high	
   liquid	
   fuel	
   yields	
   and	
   raw	
   material	
   for	
   value-­‐added	
   products	
   at	
   low	
   costs.11,12	
   Fast	
  
pyrolysis	
  involves	
  rapidly	
  heating	
  biomass	
  to	
  temperatures	
  between	
  400	
  °C	
  and	
  600	
  °C	
  in	
  
the	
   absence	
   of	
   oxygen.12	
   The	
   decomposition	
   of	
   biomass	
   during	
   the	
   fast	
   pyrolysis	
   process	
  
generates	
   three	
   major	
   products,	
   a	
   liquid	
   referred	
   to	
   as	
   bio-­‐oil,	
   a	
   solid	
   referred	
   to	
   as	
   bio-­‐
char,	
   and	
   a	
   non-­‐condensable	
   gas	
   rich	
   in	
   molecular	
   hydrogen,	
   carbon	
   oxides	
   and	
   light	
  
organics.	
  	
  However,	
  bio-­‐oil	
  corrosiveness	
  and	
  reactive	
  instability	
  pose	
  significant	
  barriers	
  
to	
   the	
   adoption	
   of	
   pyrolysis	
   systems.	
   Catalytic	
   stabilization	
   is	
   needed	
   to	
   produce	
   a	
   stable	
  
fuel	
  intermediate	
  that	
  is	
  compatible	
  with	
  common	
  infrastructure	
  materials	
  such	
  as	
  carbon	
  
34	
  
	
  

	
  
steel.	
   	
   Classical	
   catalytic	
   upgrading	
   is	
   usually	
   used	
   to	
   hydrogenate	
   and	
   deoxygenate	
   bio-­‐oil,	
  
a	
   process	
   that	
   occurs	
   at	
   high	
   temperature	
   and	
   pressure.	
   These	
   severe	
   conditions	
   pose	
  
significant	
   barriers	
   for	
   bio-­‐oil	
   upgrading	
   in	
   decentralized	
   facilities,	
   such	
   as	
   catalyst	
  
deactivation.	
  To	
  avoid	
  these	
  conditions,	
  electrocatalytic	
  hydrogenation	
  (ECH)	
  is	
  proposed	
  
to	
  stabilize	
  bio-­‐oil	
  under	
  mild	
  conditions	
  (25-­‐80	
  °C	
  and	
  1	
  atm).	
  	
  
As	
  lignin	
  is	
  a	
  byproduct	
  of	
  other	
  industries,	
  its	
  utilization	
  as	
  a	
  biofuel	
  feedstock	
  would	
  
be	
  beneficial.	
  This	
  effort	
  focuses	
  on	
  the	
  upgrading	
  of	
  model	
  compounds	
  of	
  lignin	
  pyrolysis	
  
via	
   electrocatalytic	
   hydrogenation	
   and	
   deoxygenation.	
   To	
   this	
   end,	
   three	
   major	
   studies	
  
were	
   conducted.	
   	
   Specifically,	
   our	
   first	
   study	
   builds	
   on	
   previous	
   work	
   done	
   on	
   phenolic	
  
monomers	
  such	
  as	
  2-­‐methoxyphenol	
  by	
  comparing	
  the	
  results	
  of	
  similar	
  experiments	
  using	
  
3-­‐methoxyphenol	
   and	
   4-­‐methoxyphenol.	
   	
   Concurrently,	
   studies	
   were	
   also	
   performed	
   on	
  
lignin	
   dimers	
   with	
   related	
   ether	
   linkages.	
   This	
   second	
   study	
   mainly	
   focuses	
   on	
   cleaving	
  
lignin-­‐specific	
  linkages	
  in	
  the	
  dimers.	
  As	
  lignin	
  is	
  converted	
  to	
  phenolic	
  monomers,	
  dimers,	
  
and	
  oligomers	
  upon	
  pyrolysis,	
  the	
  transformation	
  of	
  model	
  compounds	
  exhibiting	
  similar	
  
bonding	
  arrangements	
  is	
  an	
  indicator	
  of	
  the	
  potential	
  for	
  ECH-­‐mediated	
  depolymerization	
  
of	
  biomass	
  lignin.	
  The	
  third	
  study	
  focused	
  on	
  developing	
  better	
  ruthenium	
  loading	
  methods	
  
for	
  preparing	
  the	
  catalyst	
  by	
  assessing	
  catalyst	
  performance	
  and	
  deactivation	
  studies	
  as	
  a	
  
function	
   of	
   preparation	
   conditions.	
   	
   The	
   overall	
   scope	
   of	
   the	
   project	
   as	
   shown	
   in	
  Figure	
   2.1	
  
is	
   to	
   gain	
   an	
   understanding	
   of	
   the	
   potential	
   of	
   ECH	
   as	
   an	
   upgrading	
   process	
   for	
   lignin-­‐
derived	
   bio-­‐oil	
   by	
   exploring	
   different	
   conditions	
   and	
   catalyst	
   preparation	
   methods.	
   With	
  
the	
  success	
  of	
  this	
  process,	
  bio-­‐oil	
  produced	
  at	
  decentralized	
  depots	
  at	
  the	
  site	
  of	
  biomass	
  
harvest	
  can	
  be	
  upgraded	
  to	
  a	
  stable,	
  more	
  energy	
  dense	
  form	
  and	
  transported	
  to	
  petroleum	
  
processing	
  facilities	
  for	
  hydro-­‐processing	
  to	
  produce	
  liquid	
  fuels.	
  

35	
  
	
  

	
  

	
  
	
  

	
  

Figure	
  2.1:	
  Overall	
  scheme	
  of	
  the	
  project	
  from	
  EAP	
  lignin	
  to	
  liquid	
  fuels	
  

Experimental	
  Methods	
  
Model	
  Compounds	
  
As	
   a	
   continuation	
   of	
   previous	
   work	
   by	
   this	
   group,	
   a	
   study	
   was	
   done	
   on	
   methoxy	
  
phenols	
  with	
  the	
  methoxy	
  group	
  at	
  different	
  positions.	
  The	
  substrates	
  2-­‐methoxyphenol,	
  3-­‐
methoxyphenol	
   and	
   4-­‐methoxyphenol	
   were	
   all	
   obtained	
   from	
   Alpha	
   Aesar.	
   Electrocatalytic	
  
reduction	
   of	
   each	
   of	
   these	
   compounds	
   was	
   conducted.	
   	
   Lignin	
   dimer	
   studies	
   were	
   also	
  
conducted	
  to	
  study	
  the	
  effect	
  of	
  the	
  catalyst	
  on	
  different	
  types	
  of	
  linkages	
  found	
  in	
  lignin.	
  In	
  
this	
   study,	
   the	
   lignin	
   dimer	
   4-­‐phenoxyphenol	
   was	
   obtained	
   from	
   Sigma	
   Aldrich.	
   This	
  
compound	
  represents	
  the	
  4-­‐O-­‐5	
  type	
  linkage,	
  which	
  is	
  one	
  of	
  the	
  linkages	
  that	
  can	
  be	
  found	
  
in	
   lignin.	
   Guaiacyl	
   glycerol-­‐β-­‐guaiacyl	
   ether	
   (Dimer#1)	
   was	
   obtained	
   from	
   John	
   Ralph’s	
   lab	
  
at	
   University	
   of	
   Wisconsin.	
   Figure	
   2.2	
   shows	
   the	
   two	
   dimers	
   used.	
   Guaiacyl	
   glycerol-­‐β-­‐
guaiacyl	
  ether	
  is	
  representative	
  of	
  a	
  β-­‐O-­‐4	
  linkage	
  which	
  is	
  one	
  of	
  the	
  most	
  abundant	
  type	
  
of	
  linkages	
  found	
  in	
  lignin.	
  	
  	
  

36	
  
	
  

	
  

	
  
Figure	
  2.2:	
  Dimers	
  a)	
  4-­‐phenoxyphenol	
  (4-­O-­5)	
  b)	
  Dimer#1	
  (β-­O-­4)	
  	
  
Catalyst	
  Preparation	
  
Zorflex	
   ACC	
   (activated	
   carbon	
   cloth)	
   FM	
   100	
   was	
   used	
   to	
   support	
   the	
   ruthenium	
  
catalyst.	
   As	
   described	
   by	
   Li	
   et.	
   al.,13	
   the	
   activated	
   carbon	
   cloth	
   was	
   washed	
   overnight	
   in	
  
deionized	
   water	
   and	
   oven	
   dried	
   at	
   105	
   °C.	
   The	
   ACC	
   support	
   was	
   prepared	
   with	
   catalyst	
  
using	
   the	
   incipient	
   wetness	
   method	
   as	
   described	
   by	
   Li	
   et.	
   al.13	
   Ru(NH3)6Cl3	
   solution	
   was	
  
used	
  to	
  soak	
  each	
  1.5	
  x	
  3.0	
  cm	
  piece	
  of	
  ACC.	
  Each	
  cloth	
  was	
  immersed	
  in	
  the	
  solution	
  and	
  
soaked	
  for	
  a	
  few	
  minutes.	
  The	
  Ru/ACC	
  catalyst	
  was	
  then	
  dried	
  at	
  room	
  temperature	
  first	
  
overnight	
   and	
   stored	
   in	
   a	
   vacuum	
   dedicator	
   for	
   another	
   24	
   hours	
   then	
   reduced	
   with	
  
molecular	
  hydrogen	
  at	
  310	
  °C	
  for	
  12	
  hrs	
  in	
  a	
  Parr	
  reactor	
  (model	
  452HC).	
  	
  
Catalyst	
  Characterization	
  	
  
	
  

A	
   varian	
   710-­‐ES	
   inductively	
   coupled	
   plasma	
   optical	
   emission	
   spectrometer	
   (ICP-­‐

OES)	
   was	
   used	
   to	
   measure	
   the	
   ruthenium	
   content	
   of	
   the	
   catalyst	
   using	
   the	
   methods	
   as	
  
described	
  by	
  Li	
  et.	
  al.13	
  Standards	
  were	
  prepared	
  with	
  concentrations	
  of	
  0.08	
  ppm,	
  0.4	
  ppm,	
  
2	
   ppm,	
   10	
   ppm	
   and	
   50	
   ppm	
   using	
   RuCl3	
   to	
   construct	
   a	
   calibration	
   curve.	
   The	
   catalyst	
  
samples	
   were	
   prepared	
   by	
   digestion	
   in	
   aqua	
   regia	
   for	
   4	
   hours	
   in	
   a	
   water	
   bath	
   at	
   100	
   °C,	
  

37	
  
	
  

	
  
filtration	
   and	
   dilution	
   with	
   DI	
   water.	
   	
   Scanning	
   electron	
   microscopy	
   (SEM)	
   analyses	
   used	
  
JEOL	
  JSM-­‐7500F	
  and	
  JEOL	
  6400V	
  instruments.	
  The	
  Ru/ACC	
  was	
  mounted	
  onto	
  aluminum	
  
stubs	
   using	
   carbon	
   paste	
   and	
   dried	
   in	
   a	
   vacuum	
   overnight.	
   Analyses	
   were	
   done	
   using	
  
secondary	
  electron	
  imaging	
  and	
  energy-­‐dispersive	
  X-­‐ray	
  (EDX)	
  analysis.	
  	
  
Electrocatalytic	
  Hydrogenation	
  (ECH)	
  Setup	
  
A	
  two-­‐chambered	
  electrochemical	
  glass	
  H-­‐cell	
  was	
  used	
  to	
  conduct	
  the	
  experiments.	
  
The	
   chambers	
   were	
   separated	
   using	
   a	
   Dupont	
   Nafion-­‐117	
   membrane.	
   Ruthenium	
  
supported	
  on	
  activated	
  carbon	
  cloth	
  (Ru/ACC)	
  was	
  used	
  as	
  the	
  cathode	
  and	
  platinum	
  wire	
  
was	
  used	
  as	
  the	
  anode	
  a	
  shown	
  in	
  Figure	
  2.3	
  below.	
  An	
  Instek	
  GPR-­‐11H30D	
  power	
  supply	
  
was	
   used	
   to	
   provide	
   constant	
   electrical	
   current	
   for	
   the	
   various	
   experiments.	
   To	
   maintain	
  
constant	
  temperature	
  for	
  different	
  studies,	
  the	
  whole	
  cell	
  was	
  placed	
  in	
  a	
  water	
  bath	
  and	
  
the	
   desired	
   temperature	
   was	
   maintained	
   in	
   the	
   water	
   bath.	
   	
   After	
   the	
   cell	
   setup	
   was	
  
completed,	
   a	
   10	
   min	
   pre-­‐electrolysis	
   step	
   was	
   performed	
   on	
   the	
   catalyst	
   at	
   80mA	
   before	
  
adding	
   the	
   substrate.	
   After	
   pre-­‐electrolysis,	
   depending	
   on	
   the	
   experiment,	
   the	
   desired	
  
amount	
   of	
   substrate	
   was	
   added	
   and	
   the	
   experiment	
   was	
   run	
   at	
   the	
   desired	
   temperature	
  
and	
   current	
   density	
   for	
   4	
   hours.	
   Samples	
   (O.6	
   ml)	
   were	
   taken	
   every	
   hour	
   for	
   the	
  
methoxyphenol	
   study	
   and	
   every	
   40	
   minutes	
   for	
   the	
   dimer	
   studies.	
   Samples	
   were	
   then	
  
saturated	
   with	
   NaCl,	
   acidified	
   to	
   pH	
   1	
   and	
   extracted	
   into	
   chloroform.	
   The	
   catalyst	
   was	
  
placed	
   and	
   sonicated	
   in	
   chloroform	
   for	
   10	
   minutes,	
   and	
   filtered	
   prior	
   to	
   analysis	
   by	
   GC/MS	
  
and	
  GC/FID.	
  

38	
  
	
  

	
  

	
  
	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  Figure	
  2.3:	
  Two	
  chambered	
  H-­‐cell	
  setup	
  
The	
   electrolytes	
   used	
   for	
   the	
   methoxyphenol	
   study	
   were	
   30	
   ml	
   of	
   0.2	
   M	
   HCl	
  
(catholyte)	
  and	
  30	
  ml	
  0.2	
  M	
  phosphate	
  buffer	
  (anolyte).	
  	
  The	
  experiments	
  were	
  conducted	
  
with	
   20	
   mM	
   substrate	
   concentration	
   at	
   75	
   °C	
   and	
   60	
   mA	
   and	
   product	
   yield	
   and	
   current	
  
efficiency	
  were	
  investigated.	
  The	
  effect	
  of	
  different	
  conditions	
  on	
  product	
  yield	
  and	
  current	
  
efficiency	
   was	
   also	
   investigated	
   for	
   4-­‐phenoxyphenol.	
   The	
   varied	
   conditions	
   include:	
   1)	
  
electrolytes,	
  2)	
  substrate	
  concentration	
  and	
  3)	
  current	
  density.	
  	
  For	
  the	
  4-­‐phenoxyphenol	
  
studies	
  the	
  cathode/anode	
  electrolytes	
  used	
  were	
  30	
  ml	
  0.2	
  M	
  HCl/0.2	
  M	
  phosphate	
  buffer,	
  
0.2	
  M	
  NaCl/0.2	
  M	
  phosphate	
  buffer,	
  and	
  1	
  M	
  NaOH/1	
  M	
  NaOH.	
  	
  A	
  temperature	
  of	
  80	
  °C	
  was	
  
maintained	
   for	
   all	
   three	
   electrolytes	
   used.	
   For	
   the	
   substrate	
   concentration	
   study,	
   three	
  
different	
   concentrations	
   (25	
   mM,	
   12.5	
   mM	
   and	
   6.25	
   mM)	
   were	
   investigated	
   for	
   all	
   three	
  
electrolytes	
  at	
  100	
  mA.	
  Current	
  density	
  experiments	
  were	
  conducted	
  for	
  the	
  three	
  different	
  
electrolytes	
  at	
  80	
  °C	
  and	
  20	
  mA,	
  80	
  mA	
  and	
  100	
  mA.	
  	
  	
  
The	
  same	
  setup	
  was	
  used	
  for	
  the	
  ECH	
  of	
  Dimer#1.	
  Dimer#1	
  was	
  found	
  to	
  be	
  soluble	
  
in	
   1M	
   NaOH	
   and	
   all	
   experiments	
   involving	
   Dimer#1	
   were	
   carried	
   out	
   in	
   30	
   ml	
   1M	
   NaOH	
  

39	
  
	
  

	
  
solution	
   on	
   both	
   the	
   cathode	
   and	
   anode	
   compartments.	
   The	
   experiment	
   was	
   conducted	
   for	
  
6	
  hours	
  and	
  samples	
  were	
  collected	
  every	
  2	
  hours.	
  The	
  same	
  extraction	
  method	
  mentioned	
  
above	
  was	
  used	
  for	
  GC	
  samples.	
  	
  	
  
Catalyst	
  Deactivation	
  Studies	
  	
  
	
  

For	
   the	
   catalyst	
   deactivation	
   studies,	
   the	
   methods	
   used	
   by	
   Li	
   et	
   al.,13	
   were	
  

implemented	
  	
  The	
  same	
  ECH	
  setup	
  described	
  in	
  the	
  above	
  section	
  was	
  utilized	
  but	
  after	
  the	
  
first	
  experiment,	
  the	
  catalyst	
  was	
  washed	
  in	
  DI	
  water	
  and	
  stirred	
  overnight	
  in	
  a	
  20	
  ml	
  vial	
  
containing	
   DI	
   water.	
   The	
   next	
   day	
   the	
   same	
   washed	
   catalyst	
   was	
   used	
   to	
   run	
   the	
   second	
  
experiment	
  and	
  so	
  forth.	
  Samples	
  were	
  collected	
  from	
  the	
  cathode	
  solution	
  but	
  no	
  sample	
  
was	
   extracted	
   from	
   the	
   cloth	
   so	
   yield	
   calculation	
   did	
   not	
   take	
   in	
   o	
   account	
   the	
   organic	
  
products	
  that	
  were	
  adsorbed	
  onto	
  the	
  catalyst	
  cloth.	
  	
  
Sample	
  Analysis	
  	
  
	
  

Samples	
   were	
   analyzed	
   using	
   a	
   Shimadzu	
   QP-­‐5050A	
   GC/MS	
   (Shimadzu	
   Corp,	
  

Columbia,	
  MD).	
  Standards	
  in	
  chloroform	
  were	
  used	
  to	
  identify	
  products	
  by	
  retention	
  time	
  
and	
   to	
   construct	
   a	
   four-­‐point	
   calibration	
   curve.	
   	
   This	
   curve	
   was	
   utilized	
   to	
   determine	
  
product	
  yields	
  and	
  calculate	
  current	
  efficiency.	
  	
  
Calculations	
  	
  
o Yield	
  A	
  =	
  (Moles	
  of	
  A)	
  /	
  (Initial	
  moles	
  of	
  reactant)	
  	
  
	
  
o Selectivity	
  A	
  =	
  (Moles	
  of	
  A)	
  /	
  (Moles	
  of	
  total	
  products)	
  	
  
	
  

40	
  
	
  

	
  
o Conversion	
  =	
  (Moles	
  of	
  reactant	
  consumed)	
  /	
  (Initial	
  moles	
  of	
  reactants)	
  
	
  
o Current	
  efficiency	
  =	
  (Charge	
  used	
  generate	
  products)	
  /	
  (Total	
  charge	
  passed)	
  
	
  
o Current	
  Density	
  =	
  	
  (Current)/	
  (Unit	
  area	
  of	
  catalyst	
  used)	
  	
  
Results	
  and	
  Discussion	
  	
  	
  
Catalyst	
  Characterization	
  (ICP	
  and	
  SEM)	
  
Activated	
  carbon	
  cloth	
  is	
  an	
  ideal	
  catalyst	
  support	
  because	
  of	
  its	
  high	
  surface	
  area,	
  
stable	
  micropore	
  distribution	
  and	
  high	
  electrical	
  conductivity.14	
  All	
  catalysts	
  used	
  in	
  these	
  
studies	
   were	
   prepared	
   using	
   the	
   incipient	
   wetness	
   method	
   as	
   outlined	
   by	
   Li	
   et	
   al.13	
   ICP	
  
analysis	
   revealed	
   a	
   ruthenium	
   loading	
   of	
   3.5-­‐4.0	
   wt%,	
   which	
   was	
   found	
   to	
   be	
   consistent	
  
with	
  the	
  EDX	
  analysis	
  as	
  shown	
  in	
  Table	
  2.1.	
  	
  The	
  slight	
  differences	
  in	
  the	
  other	
  elements	
  
between	
   unloaded	
   vs.	
   loaded	
   carbon	
   cloth	
   can	
   be	
   attributed	
   to	
   the	
   differences	
   in	
   area	
  
between	
   the	
   two	
   different	
   pieces	
   of	
   carbon	
   cloth	
   analyzed.	
   Dot	
   map	
   images	
   shown	
   in	
  
Figure	
   2.4	
   a)	
   and	
   b)	
   show	
   the	
   carbon	
   cloth	
   and	
   the	
   ruthenium	
   dispersed	
   throughout	
   the	
  
carbon	
  fabric.	
  As	
  can	
  be	
  seen	
  from	
  the	
  images,	
  there	
  is	
  a	
  relatively	
  uniform	
  distribution	
  of	
  
the	
   ruthenium	
   particles.	
   X-­‐ray	
   dot	
   mapping	
   (presence/absence	
   analysis)	
   makes	
   use	
   of	
   a	
  
two-­‐dimensional	
  scanning	
  technique	
  where	
  each	
  detected	
  photon	
  appears	
  as	
  dot	
  with	
  the	
  
regions	
  of	
  high	
  concentration	
  appearing	
  brighter.	
  As	
  can	
  be	
  seen	
  from	
  Figures	
  2.5	
  and	
  2.6	
  
the	
   SEM	
   image	
   shows	
   a	
   random	
   distribution	
   of	
   the	
   ruthenium	
   particles	
   throughout	
   the	
  
cloth.	
  
	
  
	
  

41	
  
	
  

	
  
Table	
  2.1:	
  Scanning	
  electron	
  microscopy	
  elemental	
  analysis	
  using	
  EDX	
  
Element	
  	
  
ACC	
  Control	
  (wt%)	
  
Ru/ACC	
  Unused	
  (wt%)	
  
C	
  
85.54	
  
69.46	
  
Ru	
  
0.00	
  
4.06	
  
O	
  
5.91	
  
10.78	
  
Na	
  
0.27	
  
0.19	
  
Al	
  
3.08	
  
2.40	
  
Cl	
  
1.10	
  
-­‐	
  
Ca	
  
0.05	
  
0.20	
  
Zn	
  
4.05	
  
4.25	
  
Mg	
  
-­‐	
  
0.06	
  
Si	
  
-­‐	
  
0.06	
  
P	
  
-­‐	
  
1.46	
  
S	
  
-­‐	
  
0.11	
  
K	
  
-­‐	
  
6.88	
  
Fe	
  
-­‐	
  
0.07	
  
Total	
  	
  
100	
  
100	
  
	
  

	
  
Figure	
  2.4:	
  X-­‐ray	
  dot	
  map	
  analysis	
  of	
  Ru/ACC	
  for	
  carbon	
  and	
  ruthenium	
  a)	
  carbon	
  cloth	
  b)	
  
ruthenium	
  	
  

42	
  
	
  

	
  

Figure	
  2.5:	
  Scanning	
  electron	
  microscopy	
  images	
  of	
  a)	
  unloaded	
  b)	
  ruthenium	
  loaded	
  	
  

Figure	
  2.6:	
  Scanning	
  electron	
  microscopy	
  images	
  of	
  loaded	
  cloth	
  a)	
  100x	
  	
  b)	
  300x	
  

	
  

	
  

Model	
  Compound	
  Studies:	
  Methoxyphenols	
  with	
  Different	
  Methoxy	
  Group	
  Positions	
  	
  
Previous	
   work	
   by	
   this	
   group	
   has	
   demonstrated	
   the	
   successful	
   reduction	
   of	
   guaiacol,	
  
syringol	
   and	
   phenol	
   using	
   ECH	
   with	
   ruthenium	
   activated	
   carbon	
   cloth	
   catalyst.13	
   The	
   study	
  
of	
   these	
   substrates	
   is	
   relevant	
   as	
   these	
   compounds	
   are	
   common	
   products	
   of	
   lignin	
  
pyrolysis.	
  In	
  an	
  effort	
  to	
  catalogue	
  the	
  effectiveness	
  of	
  the	
  Ru/ACC	
  catalyst	
  as	
  a	
  means	
  of	
  
reduction,	
  several	
  lignin-­‐derived	
  bio-­‐oil	
  model	
  compounds	
  were	
  selected	
  as	
  reactants.	
  	
  To	
  
specifically	
  catalogue	
  the	
  effects	
  of	
  varying	
  the	
  ether	
  group	
  position	
  on	
  the	
  aromatic	
  ring,	
  
three	
   different	
   substrates	
   were	
   studied:	
   2-­‐methoxyphenol,	
   3-­‐methoxyphenol	
   and	
   4-­‐
methoxyphenol.	
  	
  For	
  all	
  reactants,	
  Ru/ACC	
  catalyst	
  was	
  used	
  for	
  6	
  hours	
  at	
  conditions	
  of	
  75	
  
43	
  
	
  

	
  
°C,	
  60	
  mA	
  and	
  catholyte	
  concentration	
  of	
  in	
  0.2	
  M	
  HCl.	
  	
  Samples	
  were	
  taken	
  every	
  hour	
  to	
  
be	
  extracted	
  and	
  analyzed	
  using	
  GC/MS.	
  	
  
	
  In	
  this	
  work,	
  two	
  pathways	
  are	
  suggested	
  for	
  the	
  reduction	
  of	
  the	
  methoxyphenol	
  to	
  
cyclohexanol.	
   As	
   shown	
   in	
   Figure	
   2.7,	
   the	
   methoxyphenol	
   might	
   be	
   reduced	
   to	
   phenol,	
  
followed	
   by	
   reduction	
   to	
   cyclohexanol;	
   or	
   reduction	
   of	
   methoxyphenol	
   to	
  
methoxycyclohexanone,	
   methoxycyclohexanol	
   and	
   then	
   to	
   cyclohexanol.	
   As	
   suggested	
   by	
  
the	
   schematic	
   in	
   Figure	
   2.8,	
   electrocatalysis	
   is	
   a	
   multistep	
   process	
   whereby	
   the	
   water	
   on	
  
the	
  anode	
  side	
  is	
  oxidized	
  to	
  H+	
  and	
  O2.	
  	
  H+	
  ions	
  travel	
  through	
  the	
  selective	
  membrane	
  to	
  
the	
  cathode	
  side	
  and	
  chemisorb	
  on	
  the	
  catalyst	
  resulting	
  in	
  a	
  metal/hydrogen	
  complex	
  (a)	
  
and	
  metal/methoxyphenol	
  complex	
  forms	
  on	
  the	
  catalyst	
  surface	
  (b).	
  In	
  steps	
  c-­‐f	
  reduction	
  
of	
   the	
   substrate	
   and	
   intermediates	
   occurs	
   by	
   addition	
   of	
   the	
   neighboring	
   hydrogens	
   that	
  
have	
  been	
  chemisorbed	
  to	
  the	
  catalyst	
  surface.	
  The	
  reduced	
  products	
  then	
  desorb	
  from	
  the	
  
catalyst	
  (g-­‐i).15,16,17	
  As	
  was	
  indicated	
  by	
  Li	
  et	
  al.	
  reduction	
  of	
  methoxyphenol	
  could	
  occur	
  via	
  
two	
   routes:	
   1)	
   the	
   reduction	
   of	
   double	
   bonds	
   forms	
   methoxycyclohexanol	
   then	
  
cyclohexanol	
   or	
   2)	
   demethoxylation	
   to	
   form	
   phenol	
   and	
   then	
   cyclohexanol.	
   	
   Parallel	
   to	
  
these	
  steps,	
  hydrogen	
  evolution	
  occurs	
  (j,k)	
  competing	
  with	
  the	
  electrocatalytic	
  reduction	
  
of	
  the	
  substrate.	
  	
  
	
  
	
  
	
  
	
  
	
  

44	
  
	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
Figure	
  2.7:	
  Reaction	
  pathways	
  for	
  the	
  reduction	
  of	
  methoxycyclohexanol	
  to	
  cyclohexanol	
  
and	
  methoxycyclohexanol	
  

	
  
Figure	
  2.8:	
  Electrocatalytic	
  hydrogenation	
  and	
  hydrogen	
  evolution	
  steps	
  18	
  
a. 2	
  H2O	
  +	
  2e-­‐	
  +	
  Ru	
  2[H]Ru	
  +2	
  OH-­‐	
  
b. Ru	
  +	
  Methoxyphenol	
  	
  [Methoxyphenol]	
  Ru	
  
c. 2[H]Ru	
  +	
  [Methoxyphenol]Ru	
  	
  [Phenol]Ru	
  +[Methanol]Ru	
  +	
  Ru	
  
d. 6[H]Ru	
  +	
  [Phenol]Ru	
  	
  [Cyclohexanol]Ru	
  +Ru	
  
e. 2[H]Ru	
  +	
  [Methoxyphenol]Ru	
  	
  [Methoxycyclohexanol]Ru	
  +	
  Ru	
  
45	
  
	
  

	
  
f. 2[H]Ru	
  +	
  [Methoxycyclohexanol]Ru	
  	
  [Cyclohexanol]Ru	
  +	
  [Methanol]Ru	
  +	
  Ru	
  
g. [Phenol]Ru	
  	
  Phenol	
  +	
  Ru	
  
h. [Methoxycyclohexanol]Ru	
  	
  Methoxycyclohexanol	
  +	
  Ru	
  
i.

[Cyclohexanol]	
  Ru	
  	
  Cyclohexanol	
  +	
  Ru	
  

j.

[H]Ru	
  +	
  H2O	
  +	
  e-­‐	
  	
  H2	
  +	
  Ru	
  +	
  OH-­‐	
  

k. [H]Ru	
  +	
  [H]Ru	
  	
  H2	
  +	
  Ru	
  
As	
   indicated	
   in	
   Figure	
   2.9	
   and	
   Table	
   2.2,	
   all	
   three	
   substrates	
   proceeded	
   via	
   the	
  
parallel	
   route	
   by	
   the	
   formation	
   of	
   phenol	
   followed	
   by	
   cyclohexanol	
   and	
   the	
   formation	
   of	
  
methoxycyclohexanol.	
  The	
  absence	
  of	
  phenol	
  in	
  the	
  samples	
  taken	
  at	
  different	
  time	
  steps	
  
during	
   each	
   experiment	
   could	
   be	
   indicative	
   of	
   the	
   fact	
   that	
   conversion	
   of	
   phenol	
   to	
  
cyclohexanol	
  might	
  be	
  happening	
  rapidly.	
  For	
  the	
  2-­‐methoxyphenol	
  and	
  4-­‐methoxyphenol	
  
cis/trans	
  isomers	
  were	
  identified.	
  A	
  mass	
  balance	
  of	
  80%	
  or	
  higher	
  and	
  conversion	
  greater	
  
than	
  80%	
  was	
  observed	
  for	
  all	
  cases	
  with	
  the	
  2-­‐methoxyphenol	
  showing	
  100%	
  conversion.	
  
A	
   slightly	
   higher	
   current	
   efficiency	
   was	
   also	
   recorded	
   for	
   2-­‐methoxyphenol.	
   The	
   current	
  
efficiency	
   of	
   these	
   reactions	
   was	
   still	
   modest	
   and	
   can	
   be	
   attributed	
   to	
   the	
   competing	
  
hydrogen	
   evolution	
   reaction.	
   Further	
   studies	
   in	
   this	
   area	
   should	
   explore	
   the	
   effect	
   of	
  
substrate	
   concentration,	
   current	
   density	
   and	
   several	
   other	
   conditions	
   to	
   see	
   the	
   effect	
   of	
  
these	
  conditions	
  on	
  improving	
  the	
  current	
  efficiency	
  of	
  the	
  system.	
  Figures	
  2.10,	
  2.11,2.12	
  
show	
   the	
   conversion,	
   product	
   yield	
   and	
   depletion	
   of	
   starting	
   material	
   over	
   the	
   course	
   of	
  
each	
   substrate	
   reduction.	
   In	
   each	
   figure	
   it	
   can	
   be	
   observed	
   that	
   for	
   each	
   time	
   point	
   the	
  
cyclohexanol	
   and	
   methoxycyclohexanol	
   yields	
   increase	
   simultaneously	
   supporting	
   the	
  
claim	
  that	
  the	
  formation	
  of	
  the	
  two	
  products	
  are	
  parallel	
  and	
  not	
  sequential.	
  	
  Figure	
  2.10	
  
shows	
  sudden	
  increase	
  in	
  the	
  amount	
  of	
  2-­‐methoxycyclohexanol,	
  this	
  could	
  be	
  due	
  to	
  the	
  

46	
  
	
  

	
  
extraction	
   of	
   this	
   product	
   from	
   the	
   cloth	
   and	
   not	
   from	
   the	
   catholyte	
   solution.	
   Product	
  
selectivity	
  appears	
  to	
  have	
  favored	
  methoxycyclohexanol	
  slightly	
  but	
  for	
  the	
  most	
  part	
  the	
  
catalyst	
  was	
  almost	
  equally	
  selective	
  toward	
  both	
  products.	
  	
  
Starting	
  Material	
  	
  

Methoxycyclohexanol	
  

Cyclohexanol	
  	
  

CE	
  

Conversion	
  

120	
  
100	
  

mole	
  %	
  

80	
  
60	
  
40	
  
20	
  
0	
  
2-­‐Methoxyphenol	
  

3-­‐Methoxyphenol	
  

4-­‐Methoxyphenol	
  

	
  

Figure	
  2.9:	
  	
  Product	
  yield,	
  amount	
  of	
  starting	
  material	
  left,	
  current	
  efficiency	
  and	
  
conversion	
  of	
  ECH	
  of	
  methoxyphenols	
  
Table	
  2.2:	
  Summary	
  table	
  of	
  yield	
  and	
  current	
  efficiency	
  of	
  ECH	
  of	
  methoxyphenols	
  
Product Yield %
Methoxy
Cyclo-

Cyclo-

Starting

Mass Balance

hexanol

hexanol

material

Reactants

(mol%)

(mol%)

(mol%)

(mol%)

CE (%)

2-Methoxyphenol

80

36

44*

--

20

3-Methoxyphenol

89

35

38

15

15

4-Methoxyphenol

84

31

35*

14

16

	
  *cis	
  +	
  trans	
  

47	
  
	
  

	
  
Table	
  2.3:	
  Summary	
  table	
  of	
  selectivity	
  and	
  conversion	
  of	
  ECH	
  of	
  methoxyphenols	
  
Selectivity	
  

Selectivity	
  

Cyclohexanol	
  

Methoxycyclohexanol	
  	
  

Reactants	
  	
  

Conversion	
  (mol%)	
  

(mol%)	
  	
  

(mol%)	
  

2-­‐Methoxyphenol	
  

100	
  

45	
  

55	
  

3-­‐Methoxyphenol	
  

84	
  

50	
  

50	
  

4-­‐Methoxyphenol	
  

86	
  

46	
  

54	
  

	
  
2-­‐Methoxyphenol	
  

120	
  
Conversion	
  	
  

100	
  

Cyclohexanol	
  

2-­‐Methoxycyclohexanol	
  

2-­‐Methoxyphenol	
  

mole	
  %	
  

80	
  
60	
  
40	
  
20	
  
0	
  
0	
  

200	
  

400	
  

600	
  

800	
  

1000	
  

1200	
  

1400	
  

Charge	
  Passed	
  (C)	
  

Figure	
  2.10:	
  Conversion,	
  product	
  yield	
  and	
  depletion	
  of	
  starting	
  material	
  of	
  ECH	
  of	
  2-­‐
methoxyphenol	
  

48	
  
	
  

	
  

	
  
3-­‐Methoxyphenol	
  
120	
  

Conversion	
  	
  

Cycohexanol	
  	
  

3-­‐Methoxycyclohexanol	
  

3-­‐Methoxyphenol	
  

100	
  

mole	
  %	
  

80	
  
60	
  
40	
  
20	
  
0	
  
0	
  

200	
  

400	
  

600	
  

800	
  

1000	
  

1200	
  

1400	
  

Charge	
  Passed	
  (C)	
  

Figure	
  2.11:	
  Conversion,	
  product	
  yield	
  and	
  depletion	
  of	
  starting	
  material	
  of	
  ECH	
  of	
  3-­‐
methoxyphenol	
  
	
  
4-­‐Methoxyphenol	
  
120	
  
Conversion	
  

Cyclohexanol	
  

4-­‐Methoxycyclohexanol	
  

4-­‐Methoxyphenol	
  

100	
  

mole	
  	
  %	
  

80	
  
60	
  
40	
  
20	
  
0	
  
0	
  

200	
  

400	
  

600	
  

800	
  

1000	
  

1200	
  

1400	
  

Charge	
  Passed	
  (C)	
  

Figure	
  2.12:	
  Conversion,	
  product	
  yield	
  and	
  depletion	
  of	
  starting	
  material	
  of	
  ECH	
  of	
  4-­‐
methoxyphenol	
  
	
  

49	
  
	
  

	
  

	
  
Model	
  Compound	
  Studies:	
  4-­O-­5	
  Type	
  Linkage	
  (4-­phenoxyphenol)	
  
Electrocatalysis	
   of	
   the	
   lignin	
   model	
   compound	
   4-­‐phenoxyphenol	
   (a	
   lignin	
   dimer)	
  
was	
   conducted	
   using	
   a	
   divided	
   voltaic	
   cell	
   with	
   ruthenium	
   on	
   activated	
   carbon	
   cloth	
  
(Ru/ACC)	
   and	
   HCl,	
   NaCl	
   or	
   NaOH	
   as	
   electrolytes.	
   4-­‐Phenoxyphenol	
   is	
   a	
   dimer	
   that	
   is	
  
representative	
  of	
  the	
  4-­‐O-­‐5	
  bonds	
  present	
  in	
  lignin.	
  Previous	
  studies	
  done	
  by	
  Dabo	
  et	
  al.	
  on	
  
4-­‐phenoxyphenol	
   were	
   able	
   to	
   achieve	
   the	
   cleavage	
   of	
   C-­‐O	
   bond	
   using	
   several	
   transition	
  
metals	
   embedded	
   on	
   reticulated	
   vitreous	
   carbon	
   (RVC).	
   These	
   results	
   report	
   conversion	
   to	
  
phenol	
   and	
   production	
   of	
   trace	
   amounts	
   of	
   cyclohexanol	
   and	
   cyclohexanone.19	
   Our	
   initial	
  
results	
  reveal	
  that	
  the	
  electrochemical	
  reduction	
  of	
  4-­‐phenoxyphenol	
  leads	
  to	
  cyclohexanol	
  
and	
   phenol.	
   	
   This	
   study	
   was	
   used	
   to	
   demonstrate	
   the	
   effectiveness	
   of	
   this	
   technique	
   for	
  
reducing	
  4-­‐O-­‐5	
  type	
  linkages	
  in	
  lignin.	
  	
  As	
  dimers	
  similar	
  to	
  4-­‐phenoxyphenol	
  exist	
  in	
  the	
  
bio-­‐oils	
  of	
  fast	
  pyrolysis,	
  these	
  results	
  are	
  informative	
  for	
  the	
  ECH	
  treatment	
  of	
  bio-­‐oil	
  for	
  
further	
   stabilization.	
   	
   In	
   previous	
   work,	
   lignin	
   model	
   compounds	
   and	
   products	
   of	
   lignin	
  
pyrolysis	
   were	
   examined	
   to	
   map	
   the	
   reaction	
   pathways	
   for	
   the	
   reduction	
   of	
   each	
  
component.	
  	
  In	
  all	
  cases,	
  phenolic	
  monomers	
  from	
  lignin	
  pyrolysis	
  were	
  reduced	
  via	
  ECH.	
  	
  
Upon	
   ECH	
   of	
   alkoxyphenols	
   (phenol,	
   syringol	
   and	
   guaiacol),	
   significant	
   amounts	
   of	
  
alkoxycyclohexanol	
   and	
   cyclohexanol	
   were	
   formed,	
   clearly	
   showing	
   the	
   potential	
   for	
  
chemical	
  reduction.13	
  However,	
  the	
  modest	
  current	
  efficiency	
  (electrons	
  used	
  to	
  form	
  the	
  
product	
   divided	
   by	
   electrons	
   supplied)	
   implies	
   that	
   further	
   investigation	
   of	
   electrode	
  
materials	
  and	
  their	
  optimization	
  is	
  needed.	
  	
  	
  
Electrocatalytic	
   hydrogenation	
   of	
   organic	
   compounds	
   is	
   suggested	
   to	
   occur	
   via	
   a	
  
multi-­‐reaction	
  pathway	
  as	
  described	
  by	
  Mahdavi	
  et	
  al.20	
  In	
  this	
  reaction	
  network,	
  hydrogen	
  
that	
  is	
  produced	
  by	
  the	
  electroreduction	
  of	
  water	
  is	
  chemisorbed	
  to	
  the	
  electrode	
  surface	
  
50	
  
	
  

	
  
(a),	
   causing	
   the	
   organic	
   substrate	
   to	
   be	
   reduced	
   (b-­‐f).	
   	
   At	
   the	
   same	
   time,	
   neighboring	
  
hydrogen	
  atoms	
  react	
  to	
  form	
  molecular	
  hydrogen,	
  which	
  desorbs	
  from	
  the	
  electrode	
  (g,h).	
  	
  
The	
   hydrogen	
   evolution	
   reaction	
   competes	
   with	
   organic	
   substrate	
   hydrogenation	
   and	
  
lowers	
  the	
  current	
  efficiency.20,	
   21	
  As	
  this	
  competition	
  between	
  the	
  two	
  reactions	
  is	
  highly	
  
dependant	
   on	
   the	
   reaction	
   conditions,21	
   this	
   study	
   measured	
   the	
   effects	
   of	
   different	
  
electrolytes,	
  substrate	
  concentration	
  and	
  current	
  densities.	
  	
  
a. 2	
  H2O	
  +	
  2e-­‐	
  +	
  Ru	
  2[H]Ru	
  +2	
  OH-­‐	
  
b. Ru	
  +	
  4-­‐phenoxyphenol	
  	
  [4-­‐phenoxyphenol	
  ]Ru	
  
a. 2[H]Ru	
  +	
  [4-­‐phenoxyphenol	
  ]Ru	
  	
  2[Phenol]Ru	
  +	
  Ru	
  
b. 4[H]Ru	
  +	
  [Phenol]Ru	
  	
  [Cyclohexanone]Ru	
  +Ru	
  
c. 2[H]Ru	
  +	
  [Cyclohexanone]Ru	
  	
  [Cyclohexanol]Ru	
  +	
  Ru	
  
d. 2[Phenol]Ru	
  	
  2Phenol	
  +	
  Ru	
  
e. [Cyclohexanone]Ru	
  	
  Cyclohexanone	
  +	
  Ru	
  
f. [Cyclohexanol]Ru	
  	
  Cyclohexanol	
  +	
  Ru	
  
g. [H]Ru	
  +	
  H2O	
  +	
  e-­‐	
  	
  H2	
  +	
  Ru	
  +	
  OH-­‐	
  
h. [H]Ru	
  +	
  [H]Ru	
  	
  H2	
  +	
  Ru	
  
Electrolyte	
  Effect	
  
	
  As	
   shown	
   in	
   Table	
   2.4,	
   three	
   different	
   electrolytes	
   were	
   used	
   to	
   conduct	
   the	
   ECH	
  
treatments	
   and	
   determine	
   current	
   efficiency	
   on	
   12.5	
   mM	
   4-­‐phenoxyphenol.	
   Results	
  
indicated	
   that	
   the	
   Ru/ACC	
   catalyst	
   did	
   reduce	
   4-­‐phenoxyphenol	
   to	
   phenol	
   and	
  
cyclohexanol.	
  ECH	
  can	
  effectively	
  cleave	
  ether	
  bonds	
  in	
  lignin	
  dimers	
  provided	
  that	
  ether	
  
bond	
  hydrogenolysis	
  is	
  faster	
  than	
  the	
  hydrogenation	
  of	
  the	
  aromatic	
  rings.20	
  Both	
  phenol	
  

51	
  
	
  

	
  
and	
   cyclohexanol	
   were	
   found	
   to	
   be	
   the	
   reduction	
   products	
   for	
   basic	
   and	
   neutral	
   conditions	
  
in	
   the	
   catholyte	
   as	
   seen	
   in	
   Table	
   2.4.	
   However,	
   there	
   is	
   also	
   a	
   possibility	
   of	
   cleaving	
   the	
  
ether	
   bond	
   to	
   form	
   hydroquinone,	
   benzene	
   and	
   reduction	
   of	
   hydroquinone.	
   Although	
   none	
  
of	
   these	
   two	
   products	
   were	
   observed	
   in	
   solution,	
   there	
   was	
   an	
   unidentified	
   product	
  
recovered	
  from	
  the	
  cloth,	
  which	
  could	
  be	
  a	
  reduction	
  product	
  of	
  hydroquinone	
  and	
  account	
  
for	
  closing	
  the	
  mass	
  balance.	
  	
  Acidic	
  conditions	
  did	
  produce	
  phenol	
  and	
  cyclohexanol	
  but	
  in	
  
such	
  trace	
  amounts	
  that	
  they	
  could	
  not	
  be	
  quantified	
  and	
  so	
  are	
  not	
  reported	
  in	
  this	
  case.	
  
Phenol	
  is	
  the	
  suspected	
  intermediate	
  as	
  cyclohexanol	
  was	
  observed	
  at	
  higher	
  amounts	
  for	
  
both	
   electrolytes.	
   	
   The	
   reaction	
   pathway	
   in	
   Figure	
   2.13	
   depicts	
   the	
   proposed	
   ether	
   bond	
  
cleavage	
   producing	
   phenol	
   before	
   hydrogenation	
   saturates	
   the	
   aromatic	
   ring.	
   As	
   was	
  
observed	
   from	
   the	
   results	
   below,	
   NaOH	
   was	
   found	
   to	
   be	
   the	
   best	
   electrolyte	
   with	
   higher	
  
phenol	
   and	
   cyclohexanol	
   yields	
   and	
   higher	
   current	
   efficiency.	
   	
   This	
   could	
   be	
   because	
   the	
  
base	
  dissolves	
  phenol	
  by	
  deprotonating	
  it.	
  	
  	
  

	
  
Figure	
  2.13:	
  Suggested	
  reaction	
  pathway	
  for	
  ECH	
  of	
  4-­‐phenoxyphenol	
  	
  
Table	
  2.4:	
  Summary	
  table	
  of	
  ECH	
  of	
  4-­‐phenoxyphenol	
  using	
  different	
  electrolytes	
  	
  
Cathode	
  
Electrolyte	
  
1M	
  NaOH	
  

Current	
  
(mA)	
  	
  
80	
  

Phenol	
  Yield	
  
(mol%)	
  	
  
21	
  

Cyclohexanol	
  Yield	
  
(mol%)	
  
26	
  

Conversion	
  
(mol%)	
  
97	
  

CE	
  
(%)	
  
29	
  

	
  

100	
  

13	
  

29	
  

99	
  

21	
  

0.2M	
  NaCl	
  

80	
  

9	
  

16	
  

97	
  

16	
  

	
  

100	
  

8	
  

10	
  

98	
  

10	
  

	
  

52	
  
	
  

	
  
Current	
  Density	
  and	
  Substrate	
  Concentration	
  
	
  

Different	
  current	
  density	
  studies	
  were	
  performed	
  at	
  20	
  mA,	
  80	
  mA	
  and	
  100	
  mA	
  for	
  a	
  

substrate	
  concentration	
  of	
  12.5	
  mM	
  for	
  4	
  hours	
  with	
  NaOH	
  as	
  the	
  electrolyte.	
  The	
  substrate	
  
concentration	
   studies	
   were	
   conducted	
   at	
   100	
   mA	
   with	
   three	
   different	
   substrate	
  
concentrations	
   of	
   6.25	
   mM,	
   12.5	
   mM	
   and	
   25	
   mM.	
   Results	
   summarized	
   in	
   Table	
   2.5	
   indicate	
  
that	
   at	
   low	
   current	
   density	
   production	
   of	
   phenol	
   is	
   favored	
   but	
   conversion	
   remains	
   low	
  
indicating	
   that	
   the	
   complete	
   conversion	
   of	
   4-­‐phenoxyphenol	
   was	
   not	
   achieved.	
   	
   In	
   the	
   case	
  
of	
   the	
   lower	
   current	
   density	
   experiment	
   small	
   amounts	
   of	
   cyclohexanone	
   were	
   also	
  
detected	
   on	
   the	
   cloth.	
   Higher	
   current	
   density	
   favored	
   the	
   production	
   of	
   cyclohexanol.	
   As	
  
suggested	
   by	
   Dalavoy	
   et	
   al.,	
   this	
   could	
   be	
   due	
   to	
   the	
   increase	
   of	
   surface	
   hydrogen	
   with	
  
increased	
   current	
   density	
   resulting	
   in	
   subsequent	
   increase	
   of	
   cyclohexanol	
   yield.22	
   But	
   this	
  
could	
   also	
   mean	
   an	
   increase	
   in	
   the	
   competing	
   hydrogen	
   evolution	
   reaction	
   resulting	
   in	
   low	
  
current	
   efficiency.	
   As	
   was	
   observed	
   from	
   the	
   current	
   density	
   experiments,	
   current	
  
efficiency	
   comparisons	
   indicate	
   that	
   the	
   lower	
   current	
   density	
   had	
   the	
   best	
   current	
  
efficiency	
   results	
   while	
   current	
   efficiency	
   decreased	
   for	
   higher	
   current	
   density	
  
experiments.	
  At	
  lower	
  current	
  density	
  the	
  formation	
  of	
  cyclohexanol	
  was	
  lower	
  but	
  seemed	
  
to	
   increase	
   as	
   current	
   density	
   increased	
   suggesting	
   that	
   conversion	
   of	
   phenol	
   to	
  
cyclohexanol	
   requires	
   more	
   adsorbed	
   hydrogen	
   to	
   proceed	
   compared	
   to	
   the	
   initial	
  
formation	
  of	
  phenol	
  from	
  starting	
  material.	
  Additionally	
  the	
  presence	
  of	
  cyclohexanone	
  at	
  
lower	
   current	
   density	
   indicates	
   that	
   conversion	
   of	
   phenol	
   to	
   cyclohexanone,	
   and	
   then	
   to	
  
cyclohexanol	
  is	
  happening	
  at	
  a	
  slower	
  rate	
  due	
  to	
  low	
  surface	
  hydrogen	
  concentration.	
  	
  	
  For	
  
the	
   substrate	
   concentration	
   studies,	
   lower	
   substrate	
   concentration	
   (6.25	
   mM)	
   favored	
  
better	
   cyclohexanol	
   and	
   phenol	
   yield	
   with	
   current	
   efficiency	
   slightly	
   lower	
   than	
   that	
   for	
  
53	
  
	
  

	
  
12.5	
  mM	
  substrate	
  concentration.	
  	
  25	
  mM	
  showed	
  the	
  least	
  conversion,	
  current	
  efficiency	
  
as	
  well	
  as	
  product	
  yield.	
  	
  Overall,	
  it	
  can	
  be	
  concluded	
  that	
  higher	
  current	
  density	
  and	
  low	
  
substrate	
  concentration	
  favored	
  high	
  cyclohexanol	
  yield	
  while	
  low	
  current	
  density	
  ws	
  more	
  
selective	
  towards	
  phenol	
  formation.	
  	
  
Table	
  2.5:	
  Summary	
  of	
  ECH	
  of	
  4-­‐phenoxyphenol	
  with	
  different	
  current	
  density	
  and	
  
substrate	
  concentration	
  
Cyclohexanol	
  
Concentration	
  
Current	
  	
  
Phenol	
  Yield	
  
Yield	
  
Conversion	
  
CE	
  
(mM)	
  
(mA)	
  
(mol%)	
  	
  
(mol%)	
  
(mol%)	
  
(%)	
  
12.5	
  
20	
  
40	
  
19	
  
90	
  	
  
98	
  	
  
12.5	
  

80	
  

21	
  

26	
  

97	
  

29	
  

12.5	
  

100	
  

13	
  

29	
  

99	
  

20	
  

6.25	
  

100	
  

28	
  

54	
  

96	
  

18	
  

25.0	
  

100	
  

11	
  

7	
  

67	
  

11	
  

	
  
Model	
  Compound	
  Studies:	
  β-­O-­4	
  type	
  Linkage	
  Dimers	
  
Some	
   studies	
   have	
   shown	
   the	
   successful	
   cleavage	
   of	
   lignin	
   model	
   dimers	
   using	
  
Raney	
  nickel.15	
  So	
  the	
  effect	
  of	
  Ru/ACC	
  on	
  β-­‐O-­‐4	
  type	
  linkage	
  dimers	
  was	
  the	
  next	
  step	
  in	
  
this	
  study	
  as	
  these	
  types	
  of	
  linkages	
  are	
  the	
  most	
  abundant	
  in	
  lignin.	
  However,	
  the	
  results	
  
reported	
   here	
   are	
   only	
   preliminary	
   and	
   further	
   quantification	
   of	
   reactant	
   concentration	
  
and	
   product	
   yields	
   is	
   needed.	
   	
   Initial	
   testing	
   of	
   this	
   synthetic	
   dimer	
   shows	
   promising	
  
results	
  with	
  its	
  cleavage	
  to	
  guaiacol	
  and	
  vanillin	
  (Figure	
  2.14)	
  along	
  with	
  other	
  unidentified	
  
products.	
   	
   These	
   products	
   are	
   expected	
   given	
   the	
   reaction	
   chemistries	
   that	
   have	
   been	
  
previously	
  observed	
  with	
  4-­‐phenoxyphenol.	
  	
  	
  	
  

54	
  
	
  

	
  

	
  
Figure	
  2.14:	
  Reaction	
  conditions	
  and	
  products	
  of	
  ECH	
  of	
  dimer	
  #1	
  	
  
Catalyst	
  Deactivation	
  
	
  

Catalyst	
   deactivation	
   is	
   an	
   important	
   phenomenon	
   that	
   needs	
   to	
   be	
   understood	
  

before	
  the	
  design	
  phase	
  of	
  a	
  catalytic	
  process.	
  Minimizing	
  catalyst	
  deactivation	
  over	
  time	
  is	
  
essential	
   to	
   ensure	
   the	
   cost	
   effectiveness	
   of	
   catalyst	
   use	
   as	
   well	
   as	
   process	
   efficiency,	
  
product	
   yield	
   and	
   selectivity.	
   A	
   catalyst	
   that	
   can	
   maintain	
   high	
   activity	
   and	
   selectivity	
  
towards	
   desired	
   products	
   over	
   time	
   is	
   essential.23	
   Ideally,	
   catalysts	
   should	
   remain	
  
unaltered	
   by	
   the	
   process	
   they	
   catalyze;	
   but	
   oftentimes	
   catalyst	
   deactivation	
   occurs	
   by	
   a	
  
variety	
   of	
   mechanisms.	
   It	
   is	
   important	
   to	
   determine	
   the	
   onset,	
   cause,	
   mechanism	
   and	
  
solutions	
   to	
   catalyst	
   deactivation.	
   Catalyst	
   deactivation	
   is	
   known	
   to	
   occur	
   via	
   various	
  
mechanisms	
   such	
   as	
   poisoning,	
   sintering,	
   coking	
   or	
   fouling	
   and	
   phase	
   transformation.24	
  
Poisoning	
   is	
   the	
   loss	
   of	
   activity	
   due	
   to	
   the	
   blocking	
   of	
   the	
   active	
   sites	
   by	
   strongly	
  
chemisorbed	
   impurities;	
   sintering	
   is	
   thermally	
   induced	
   structural	
   modification	
   of	
   the	
  
catalyst;	
   coking	
   can	
   occur	
   through	
   blocking	
   of	
   the	
   catalyst	
   surface	
   with	
   carbonaceous	
  
residue.25	
   Phase	
   transformation	
   occurs	
   due	
   to	
   high	
   temperature	
   effects	
   whereby	
   the	
  
morphology	
  of	
  the	
  catalyst	
  is	
  changed.	
   26	
  In	
  this	
  study,	
  it	
  is	
  important	
  to	
  determine	
  the	
  life	
  

55	
  
	
  

	
  
span	
  of	
  the	
  catalyst	
  and	
  if	
  catalyst	
  deactivation	
  does	
  occur,	
  it	
  is	
  beneficial	
  to	
  understand	
  the	
  
mechanism	
  by	
  which	
  deactivation	
  occurs.	
  	
  
	
  

In	
  this	
  study	
  five	
  experiments	
  were	
  run	
  using	
  the	
  same	
  catalyst.	
  After	
  each	
  use,	
  the	
  

catalyst	
   was	
   washed	
   overnight	
   in	
   DI	
   water.	
   Each	
   time	
   the	
   same	
   area	
   of	
   the	
   catalyst	
   was	
  
used	
   to	
   assure	
   no	
   variation	
   in	
   activity	
   from	
   using	
   an	
   area	
   that	
   was	
   not	
   used	
   previously.	
  
Samples	
   were	
   taken	
   every	
   40	
   minutes,	
   extracted	
   and	
   analyzed	
   using	
   GC/MS.	
   In	
   each	
  
experiment,	
  a	
  10	
  minute	
  pre-­‐electrolysis	
  step	
  was	
  performed	
  to	
  activate	
  the	
  catalyst.	
  In	
  this	
  
case,	
  products	
  adsorbed	
  to	
  the	
  activated	
  carbon	
  of	
  the	
  catalyst	
  were	
  not	
  accounted	
  for	
  at	
  
the	
  end	
  of	
  the	
  experiment.	
  Usually,	
  the	
  cloth	
  would	
  be	
  sonicated	
  in	
  chloroform	
  to	
  extract	
  
adsorbed	
   products	
   such	
   as	
   cyclohexanol.	
   In	
   previous	
   deactivation	
   experiments,	
   the	
   cloth	
  
was	
   sonicated	
   in	
   chloroform	
   after	
   each	
   experiment,	
   but	
   this	
   treatment	
   led	
   to	
   complete	
  
deactivation	
  of	
  the	
  catalyst.	
  This	
  could	
  be	
  due	
  to	
  the	
  poisoning	
  of	
  the	
  catalyst	
  by	
  chloride,	
  
or	
   caused	
   by	
   the	
   complete	
   blockage	
   of	
   active	
   sites	
   by	
   chloroform	
   or	
   its	
   breakdown	
  
products.	
  In	
  subsequent	
  studies	
  the	
  cloth	
  was	
  only	
  washed	
  in	
  DI	
  water	
  to	
  avoid	
  any	
  further	
  
deactivation	
   effects	
   caused	
   by	
   the	
   use	
   of	
   chloroform.	
   The	
   results	
   of	
   this	
   study	
   are	
  
summarized	
   in	
   Table	
   2.6.	
   Phenol	
   yield	
   decreased	
   with	
   every	
   use.	
   Cyclohexanol	
   yield	
  
increased	
   from	
   first	
   use	
   to	
   second	
   use,	
   which	
   can	
   be	
   attributed	
   to	
   residual	
   cyclohexanol	
   on	
  
the	
   cloth	
   from	
   the	
   first	
   use.	
   A	
   similar	
   trend	
   can	
   also	
   be	
   observed	
   in	
   the	
   apparent	
   current	
  
efficiency	
  data;	
  due	
  to	
  the	
  increase	
  in	
  moles	
  of	
  cyclohexanol	
  observed	
  for	
  the	
  second	
  use,	
  
the	
  current	
  efficiency	
  was	
  also	
  highest	
  for	
  the	
  second	
  trial	
  (Figure	
  2.16).	
  After	
  the	
  second	
  
use	
   the	
   cyclohexanol	
   yield	
   follows	
   the	
   same	
   trends	
   as	
   that	
   for	
   phenol;	
   the	
   cyclohexanol	
  
yield	
  continues	
  to	
  drop	
  after	
  each	
  experiment,	
  as	
  does	
  the	
  current	
  efficiency.	
  	
  The	
  overall	
  
product	
  yield	
  (phenol	
  +	
  cyclohexanol)	
  decreased	
  from	
  one	
  experiment	
  to	
  the	
  next	
  (Figure	
  

56	
  
	
  

	
  
2.15).	
   Initial	
   selectivity	
   was	
   higher	
   for	
   phenol,	
   but	
   after	
   the	
   first	
   experiment,	
   selectivity	
  
increased	
   for	
   cyclohexanol.	
   A	
   change	
   in	
   selectivity	
   is	
   often	
   a	
   sign	
   that	
   some	
   change	
   has	
  
occurred	
  in	
  the	
  catalyst	
  and	
  could	
  be	
  a	
  possible	
  indication	
  of	
  catalyst	
  deactivation.	
  But	
  most	
  
likely	
   this	
   switch	
   in	
   selectivity	
   could	
   be	
   attributed	
   to	
   the	
   fact	
   that	
   cyclohexanol	
   is	
   captured	
  
on	
   the	
   ACC	
   but	
   phenol	
   is	
   not	
   captured	
   on	
   the	
   cloth	
   in	
   any	
   of	
   the	
   5	
   experiments	
   resulting	
   in	
  
more	
   phenol	
   than	
   cyclohexanol	
   in	
   solution	
   after	
   each	
   run.	
   For	
   the	
   first	
   two	
   trials,	
  
conversion	
  was	
  close	
  to	
  100%,	
  after	
  the	
  second	
  trial,	
  conversion	
  gradually	
  decreased	
  with	
  
the	
  fifth	
  reuse	
  falling	
  lower	
  than	
  40%	
  (Figure	
  2.17).	
  	
  	
  
Table	
  2.6:	
  Summary	
  table	
  of	
  catalyst	
  deactivation	
  study	
  
Cyclohexanol	
  
Phenol	
  
Cyclohexanol	
  
Phenol	
  Yield	
  

Yield	
  

Selectivity	
  

Selectivity	
  

Conversion	
  

CE	
  

Use	
  

(mol%)	
  

(mol%)	
  

(mol%)	
  

(mol%)	
  

(mol%)	
  

(%)	
  

1	
  

18.13	
  

14.58	
  

55.43	
  

44.57	
  

99.81	
  

12.51	
  

2	
  

9.68	
  

18.03	
  

34.95	
  

65.05	
  

98.23	
  

13.96	
  

3	
  

7.38	
  

16.16	
  

31.37	
  

68.62	
  

88.14	
  

10.28	
  

4	
  

7.02	
  

14.19	
  

33.10	
  

66.90	
  

73.77	
  

10.61	
  

5	
  

6.46	
  

13.69	
  

32.07	
  

67.93	
  

38.35	
  

10.12	
  

	
  
35	
  

1st	
  Use	
  	
  
2nd	
  Use	
  
3rd	
  Use	
  
4th	
  Use	
  
5th	
  Use	
  

30	
  
%	
  Yield	
  	
  

25	
  
20	
  
15	
  
10	
  
5	
  
0	
  
0	
  

200	
  

400	
  

600	
  
800	
  
1000	
  
Total	
  Charge	
  (C)	
  

1200	
  

1400	
  

1600	
  

	
  	
  	
  
Figure	
  2.15:	
  Product	
  yield	
  (phenol	
  +	
  cyclohexanol)	
  for	
  catalyst	
  deactivation	
  test	
  	
  	
  
57	
  
	
  

	
  
	
  

%	
  Current	
  Ef•iciency	
  	
  

50	
  
45	
  
40	
  
35	
  
30	
  
25	
  
20	
  
15	
  
10	
  
5	
  
0	
  

1st	
  Use	
  
2nd	
  Use	
  
3rd	
  Use	
  
4th	
  Use	
  
5th	
  Use	
  

0	
  

200	
  

400	
  

600	
  
800	
  
1000	
  
Total	
  Charge	
  (C)	
  

1200	
  

1400	
  

1600	
  

Figure	
  2.16:	
  Current	
  efficiency	
  for	
  catalyst	
  deactivation	
  test	
  	
  

	
  

120	
  
1st	
  Use	
  
2nd	
  Use	
  
3rd	
  Use	
  
4th	
  Use	
  
5th	
  Use	
  	
  

%	
  Conversion	
  	
  

100	
  
80	
  
60	
  
40	
  
20	
  
0	
  
0	
  

200	
  

400	
  

600	
  
800	
  
1000	
  
Total	
  Charge	
  (C)	
  

1200	
  

1400	
  

Figure	
  2.17:	
  Conversion	
  for	
  catalyst	
  deactivation	
  test	
  	
  	
  

1600	
  

	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  

Conclusion	
  
Methoxyphenol	
  studies	
  clearly	
  indicated	
  that	
  the	
  position	
  of	
  the	
  methoxy	
  group	
  on	
  
the	
  aromatic	
  ring	
  did	
  not	
  have	
  a	
  significant	
  effect	
  on	
  the	
  selected	
  path	
  of	
  product	
  formation	
  
or	
   the	
   yields	
   of	
   methoxycyclohexanol	
   and	
   cyclohexanol.	
   In	
   the	
   case	
   of	
   2-­‐methoxyphenol	
  
and	
  4-­‐methoxyphenol	
  the	
  formation	
  of	
  cis	
  and	
  trans	
  isomers	
  of	
  the	
  methoxycyclohexanol	
  
were	
   observed.	
   These	
   studies	
   proved	
   the	
   effectiveness	
   of	
   the	
   catalyst	
   in	
   reducing	
  

58	
  
	
  

	
  
methoxyphenols	
   to	
   cyclohexanol	
   and	
   methoxycyclohexanol	
   regardless	
   of	
   the	
   position	
   of	
  
the	
  methoxy	
  group	
  on	
  the	
  aromatic	
  ring.	
  	
  
From	
   the	
   4-­‐phenoxyphenol	
   studies	
   a	
   maximum	
   cyclohexanol	
   yield	
   of	
   54%	
   was	
  
measured	
   when	
   NaOH	
   was	
   used	
   as	
   electrolyte	
   at	
   100	
   mA	
   for	
   four	
   hours	
   with	
   6.25	
   mM	
  
substrate	
   concentration.	
   	
   This	
   trial	
   also	
   resulted	
   in	
   a	
   current	
   efficiency	
   of	
   18%,	
   with	
   the	
  
inefficiency	
   due	
   to	
   molecular	
   hydrogen	
   production.	
   Although	
   it	
   was	
   observed	
   that	
   high	
  
current	
  efficiency	
  was	
  recorded	
  for	
  low	
  current	
  density	
  experiments,	
  it	
  resulted	
  in	
  higher	
  
phenol	
  selectivity,	
  which	
  can	
  be	
  beneficial.	
  It	
  is	
  important	
  to	
  note	
  that	
  current	
  efficiencies	
  
are	
  likely	
  far	
  from	
  optimized,	
  and	
  that	
  varying	
  conditions	
  such	
  as	
  current	
  density,	
  electrode	
  
materials,	
   electrolytes,	
   electrolyte	
   concentrations,	
   substrate	
   concentration	
   and	
  
temperature	
  may	
  further	
  improve	
  these	
  results.	
  	
  	
  
Catalyst	
   deactivation	
   studies	
   uncovered	
   a	
   decrease	
   in	
   activity	
   after	
   two	
   uses.	
   To	
  
optimize	
  current	
  efficiency	
  and	
  to	
  increase	
  the	
  service	
  life	
  of	
  the	
  system,	
  areas	
  of	
  ongoing	
  
development	
  include	
  improvements	
  in	
  cell	
  design,	
  energy	
  efficiency,	
  and	
  catalytic	
  cathode	
  
stability.	
   The	
   organic	
   chemical	
   transformations	
   described	
   here	
   also	
   have	
   synthetic	
  
potential.	
   	
   Studies	
   to	
   probe	
   selectivity,	
   the	
   mechanism	
   of	
   the	
   aryl	
   ether	
   cleavage	
   and	
   the	
  
range	
  of	
  electrocatalytically	
  convertible	
  substrates	
  are	
  also	
  underway.	
  

59	
  
	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
REFERENCES	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

60	
  
	
  

	
  
REFERENCES	
  
	
  
1.	
  

Bu,	
  Q.;	
  Lei,	
  H.;	
  Zacher,	
  A.	
  H.;	
  Wang,	
  L.;	
  Ren,	
  S.;	
  Liang,	
  J.;	
  Wei,	
  Y.;	
  Liu,	
  Y.;	
  Tang,	
  J.;	
  Zhang,	
  
Q.;	
  Ruan,	
  R.,	
  A	
  review	
  of	
  catalytic	
  hydrodeoxygenation	
  of	
  lignin-­‐derived	
  phenols	
  
from	
  biomass	
  pyrolysis.	
  Bioresource	
  Technology	
  2012,	
  124	
  (0),	
  470-­‐477.	
  

2.	
  

Pandey,	
  M.	
  P.	
  a.	
  K.,	
  C.	
  S.	
  	
  Chem.	
  Eng.	
  Technol.,	
  	
  34:	
  29–41.	
  doi:	
  
10.1002/ceat.201000270,	
  Lignin	
  Depolymerization	
  and	
  	
  Conversion:	
  A	
  Review	
  of	
  
Thermochemical	
  Methods.	
  Chem.	
  Eng.	
  Technol.:	
  2011;	
  Vol.	
  34:	
  29–41.	
  
doi:	
  10.1002/ceat.201000270.	
  

3.	
  

Mahdavi,	
  B.;	
  Lafrance,	
  A.;	
  Martel,	
  A.;	
  Lessard,	
  J.;	
  Menard,	
  H.;	
  Brossard,	
  L.,	
  
Electrocatalytic	
  hydrogenolysis	
  of	
  lignin	
  model	
  dimers	
  at	
  Raney	
  nickel	
  electrodes.	
  J.	
  
Appl.	
  Electrochem.	
  1997,	
  27	
  (5),	
  605-­‐611.	
  

4.	
  

Saiz-­‐Jimenez,	
  C.;	
  De	
  Leeuw,	
  J.	
  W.,	
  Lignin	
  pyrolysis	
  products:	
  Their	
  structures	
  and	
  
their	
  significance	
  as	
  biomarkers.	
  Organic	
  Geochemistry	
  1986,	
  10	
  (4–6),	
  869-­‐876.	
  

5.	
  

Zakzeski,	
  J.;	
  Bruijnincx,	
  P.	
  C.	
  A.;	
  Jongerius,	
  A.	
  L.;	
  Weckhuysen,	
  B.	
  M.,	
  The	
  catalytic	
  
valorization	
  of	
  lignin	
  for	
  the	
  production	
  of	
  renewable	
  chemicals.	
  Chem.	
  Rev.	
  2010,	
  
110,	
  3552-­‐3599.	
  

6.	
  

Patwardhan,	
  P.	
  R.;	
  Brown,	
  R.	
  C.;	
  Shanks,	
  B.	
  H.,	
  Understanding	
  the	
  Fast	
  Pyrolysis	
  of	
  
Lignin.	
  ChemSusChem	
  2011,	
  4	
  (11),	
  1629-­‐1636;	
  Yang,	
  H.	
  P.;	
  Yan,	
  R.;	
  Chen,	
  H.	
  P.;	
  Lee,	
  
D.	
  H.;	
  Zheng,	
  C.	
  G.,	
  Characteristics	
  of	
  hemicellulose,	
  cellulose	
  and	
  lignin	
  pyrolysis.	
  
Fuel	
  2007,	
  86	
  (12-­‐13),	
  1781-­‐1788.	
  

7.	
  

Rensel,	
  D.	
  J.;	
  Rouvimov,	
  S.;	
  Gin,	
  M.	
  E.;	
  Hicks,	
  J.	
  C.,	
  Highly	
  selective	
  bimetallic	
  FeMoP	
  
catalyst	
  for	
  C–O	
  bond	
  cleavage	
  of	
  aryl	
  ethers.	
  Journal	
  of	
  Catalysis	
  2013,	
  305	
  (0),	
  256-­‐
263.	
  

8.	
  

Gosselink,	
  R.	
  J.	
  A.;	
  de	
  Jong,	
  E.;	
  Guran,	
  B.;	
  Abacherli,	
  A.,	
  Co-­‐ordination	
  network	
  for	
  
lignin	
  -­‐	
  standardisation,	
  production	
  and	
  applications	
  adapted	
  to	
  market	
  
requirements	
  (EUROLIGNIN).	
  Industrial	
  Crops	
  and	
  Products	
  2004,	
  20	
  (2),	
  121-­‐129.	
  

9.	
  

Nowakowski,	
  D.	
  J.;	
  Bridgwater,	
  A.	
  V.;	
  Elliott,	
  D.	
  C.;	
  Meier,	
  D.;	
  de	
  Wild,	
  P.,	
  Lignin	
  fast	
  
pyrolysis:	
  Results	
  from	
  an	
  international	
  collaboration.	
  Journal	
  of	
  Analytical	
  and	
  
Applied	
  Pyrolysis	
  2010,	
  88	
  (1),	
  53-­‐72.	
  

10.	
  

Bals,	
  B.;	
  Rogers,	
  C.;	
  Jin,	
  M.;	
  Balan,	
  V.;	
  Dale,	
  B.,	
  Evaluation	
  of	
  ammonia	
  fibre	
  expansion	
  
(AFEX)	
  pretreatment	
  for	
  enzymatic	
  hydrolysis	
  of	
  switchgrass	
  harvested	
  in	
  different	
  
seasons	
  and	
  locations.	
  Biotechnology	
  for	
  Biofuels	
  C7	
  -­	
  1	
  2010,	
  3	
  (1),	
  1-­‐11.	
  

11.	
  

Lu,	
  Q.;	
  Li,	
  W.-­‐Z.;	
  Zhu,	
  X.-­‐F.,	
  Overview	
  of	
  fuel	
  properties	
  of	
  biomass	
  fast	
  pyrolysis	
  oils.	
  
Energy	
  Conversion	
  and	
  Management	
  2009,	
  50	
  (5),	
  1376-­‐1383.	
  
61	
  
	
  

	
  
12.	
  

Bridgwater,	
  A.	
  V.;	
  Meier,	
  D.;	
  Radlein,	
  D.,	
  An	
  overview	
  of	
  fast	
  pyrolysis	
  of	
  biomass.	
  
Org.	
  Geochem.	
  1999,	
  30	
  (12),	
  1479-­‐1493.	
  

13.	
  

Li,	
  Z.;	
  Garedew,	
  M.;	
  Lam,	
  C.	
  H.;	
  Jackson,	
  J.	
  E.;	
  Miller,	
  D.	
  J.;	
  Saffron,	
  C.	
  M.,	
  Mild	
  
electrocatalytic	
  hydrogenation	
  and	
  hydrodeoxygenation	
  of	
  bio-­‐oil	
  derived	
  phenolic	
  
compounds	
  using	
  ruthenium	
  supported	
  on	
  activated	
  carbon	
  cloth.	
  Green	
  Chemistry	
  
2012,	
  14	
  (9),	
  2540-­‐2549.	
  

14.	
  

Perrard,	
  A.;	
  Gallezot,	
  P.;	
  Joly,	
  J.-­‐P.;	
  Durand,	
  R.;	
  Baljou,	
  C.;	
  Coq,	
  B.;	
  Trens,	
  P.,	
  Highly	
  
efficient	
  metal	
  catalysts	
  supported	
  on	
  activated	
  carbon	
  cloths:	
  A	
  catalytic	
  
application	
  for	
  the	
  hydrogenation	
  of	
  d-­‐glucose	
  to	
  d-­‐sorbitol.	
  Applied	
  Catalysis	
  A:	
  
General	
  2007,	
  331	
  (0),	
  100-­‐104.	
  

15.	
  

Cyr,	
  A.;	
  Chiltz,	
  F.;	
  Jeanson,	
  P.;	
  Martel,	
  A.;	
  Brossard,	
  L.;	
  Lessard,	
  J.;	
  Menard,	
  H.,	
  
Electrocatalytic	
  hydrogenation	
  of	
  lignin	
  models	
  at	
  Raney	
  nickel	
  and	
  palladium-­‐
based	
  electrodes.	
  Canadian	
  Journal	
  of	
  Chemistry-­Revue	
  Canadienne	
  De	
  Chimie	
  2000,	
  
78	
  (3),	
  307-­‐315.	
  

16.	
  

Mahdavi,	
  B.;	
  Lafrance,	
  A.;	
  Martel,	
  A.;	
  Lessard,	
  J.;	
  Me´Nard,	
  H.;	
  Brossard,	
  L.,	
  
Electrocatalytic	
  hydrogenolysis	
  of	
  lignin	
  model	
  dimers	
  at	
  Raney	
  nickel	
  electrodes.	
  
Journal	
  of	
  Applied	
  Electrochemistry	
  1997,	
  27	
  (5),	
  605-­‐611.	
  

17.	
  

Ilikti,	
  H.;	
  Rekik,	
  N.;	
  Thomalla,	
  M.,	
  Electrocatalytic	
  hydrogenation	
  of	
  phenol	
  in	
  
aqueous	
  solutions	
  at	
  a	
  Raney	
  nickel	
  electrode	
  in	
  the	
  presence	
  of	
  cationic	
  surfactants.	
  
Journal	
  of	
  Applied	
  Electrochemistry	
  2002,	
  32	
  (6),	
  603-­‐609.	
  

18.	
  

Dalavoy,	
  T.	
  S.;	
  Jackson,	
  J.	
  E.;	
  Swain,	
  G.	
  M.;	
  Miller,	
  D.	
  J.,	
  Mild	
  electrocatalytic	
  
hydrogenation	
  of	
  alpha	
  functionalized	
  carboxylic	
  acids.	
  Abstracts	
  of	
  Papers	
  of	
  the	
  
American	
  Chemical	
  Society	
  2006,	
  231.	
  

19.	
  

Dabo,	
  P.;	
  Cyr,	
  A.;	
  Lessard,	
  J.;	
  Brossard,	
  L.;	
  Ménard,	
  H.,	
  Electrocatalytic	
  hydrogenation	
  
of	
  4-­‐phenoxyphenol	
  on	
  active	
  powders	
  highly	
  dispersed	
  in	
  a	
  reticulated	
  vitreous	
  
carbon	
  electrode.	
  Canadian	
  Journal	
  of	
  Chemistry-­revue	
  Canadienne	
  De	
  Chimie	
  1999,	
  
77	
  (7),	
  1225-­‐1229.	
  

20.	
  

Mahdavi,	
  B.;	
  Chambrion,	
  P.;	
  Binette,	
  J.;	
  Martel,	
  E.;	
  Lessard,	
  J.,	
  Electrocatalytic	
  
Hydrogenation	
  of	
  Conjugated	
  Enones	
  on	
  Nickel	
  Boride,	
  Nickel,	
  and	
  Raney-­‐Nickel	
  
Electrodes.	
  Can.	
  J.	
  Chem.-­Rev.	
  Can.	
  Chim.	
  1995,	
  73	
  (6),	
  846-­‐852.	
  

21.	
  

Robin,	
  D.;	
  Comtois,	
  M.;	
  Martel,	
  A.;	
  Lemieux,	
  R.;	
  Cheong,	
  A.	
  K.;	
  Belot,	
  G.;	
  Lessard,	
  J.,	
  The	
  
electrocatalytic	
  hydrogenation	
  of	
  fused	
  poly	
  cyclic	
  aromatic	
  compounds	
  at	
  Raney	
  
nickel	
  electrodes:	
  the	
  influence	
  of	
  catalyst	
  activation	
  and	
  electrolysis	
  conditions.	
  
Canadian	
  journal	
  of	
  chemistry	
  1990,	
  68	
  (7),	
  1218-­‐1227.	
  

22.	
  

Dalavoy,	
  T.	
  S.;	
  Jackson,	
  J.	
  E.;	
  Swain,	
  G.	
  M.;	
  Miller,	
  D.	
  J.;	
  Li,	
  J.;	
  Lipkowski,	
  J.,	
  Mild	
  
electrocatalytic	
  hydrogenation	
  of	
  lactic	
  acid	
  to	
  lactaldehyde	
  and	
  propylene	
  glycol.	
  
Journal	
  of	
  Catalysis	
  2007,	
  246	
  (1),	
  15-­‐28.	
  
62	
  
	
  

	
  
23.	
  

Moulijn,	
  J.	
  A.;	
  van	
  Diepen,	
  A.	
  E.;	
  Kapteijn,	
  F.,	
  Catalyst	
  deactivation:	
  is	
  it	
  predictable?:	
  
What	
  to	
  do?	
  Applied	
  Catalysis	
  A:	
  General	
  2001,	
  212	
  (1–2),	
  3-­‐16.	
  

24.	
  

Forzatti,	
  P.;	
  Lietti,	
  L.,	
  Catalyst	
  deactivation.	
  Catalysis	
  Today	
  1999,	
  52	
  (2–3),	
  165-­‐181.	
  

25.	
  

Bartholomew,	
  C.	
  H.,	
  Mechanisms	
  of	
  catalyst	
  deactivation.	
  Applied	
  Catalysis	
  A:	
  General	
  
2001,	
  212	
  (1–2),	
  17-­‐60.	
  

26.	
  

Rothenberg,	
  G.,	
  Heterogeneous	
  Catalysis.	
  In	
  Catalysis,	
  Wiley-­‐VCH	
  Verlag	
  GmbH	
  &	
  Co.	
  
KGaA:	
  2008;	
  pp	
  127-­‐187.	
  

	
  

63	
  
	
  

	
  
Chapter	
  3	
  : Characterization	
  of	
  Extractive	
  Ammonia	
  Process	
  Lignin	
  Fractions	
  	
  
Abstract	
  
Lignin	
   is	
   the	
   second	
   most	
   abundant	
   biomass	
   component	
   after	
   holocellulose	
   and	
  
accounts	
   for	
   10-­‐30%	
   of	
   the	
   lignocellulosic	
   biomass	
   by	
   weight	
   (40%	
   by	
   energy).	
   In	
   the	
  
nascent	
   alcohol-­‐based	
   biofuels	
   industry,	
   only	
   cellulose	
   and	
   part	
   of	
   the	
   hemicellulose	
   are	
  
used	
  for	
  liquids	
  production,	
  while	
  the	
  remaining	
  lignin	
  is	
  burned	
  to	
  provide	
  heat,	
  using	
  it	
  as	
  
a	
   low	
   value	
   fuel.	
   Upgrading	
   and	
   sale	
   of	
   higher	
   value	
   products	
   from	
   lignin	
   would	
   improve	
  
economics	
  of	
  liquid	
  fuel	
  bioenergy	
  systems.	
  The	
  extractive	
  ammonia	
  process	
  (EAP)	
  is	
  being	
  
considered	
  for	
  deployment	
  in	
  centralized	
  biorefineries	
  that	
  produce	
  fuel	
  alcohols	
  such	
  as	
  
ethanol	
   and	
   butanol.	
   In	
   lieu	
   of	
   combustion,	
   we	
   propose	
   to	
   convert	
   ammonia-­‐extracted	
  
lignin	
   to	
   hydrocarbon	
   fuels	
   and	
   chemicals	
   using	
   a	
   combination	
   of	
   pyrolysis	
   and	
  
electrocatalytic	
   reduction.	
   These	
   flexible,	
   simple	
   technologies	
   can	
   be	
   safely	
   deployed	
   at	
  
large	
   biorefineries	
   to	
   diversify	
   their	
   product	
   slates	
   and	
   improve	
   their	
   value	
   proposition.	
  	
  
The	
  utility	
  of	
  this	
  approach	
  can	
  also	
  be	
  realized	
  at	
  smaller,	
  decentralized	
  processing	
  depots	
  
that	
   separate	
   lignin	
   from	
   structural	
   carbohydrates.	
   In	
   this	
   study,	
   lignin	
   characterization	
  
and	
   its	
   pyrolysis	
   were	
   performed	
   in	
   an	
   effort	
   to	
   devise	
   a	
   depolymerization	
   protocol.	
  
Finally,	
  the	
  depolymerized	
  product	
  was	
  subjected	
  to	
  electrocatalysis	
  to	
  assess	
  the	
  extent	
  of	
  
value	
  addition.	
  	
  	
  
Introduction	
  	
  
Due	
  to	
  the	
  energy	
  stored	
  in	
  its	
  components,	
  biomass	
  has	
  a	
  great	
  potential	
  as	
  a	
  feedstock	
  
for	
   the	
   production	
   of	
   liquid	
   fuels	
   and	
   value	
   added	
   products.	
   Deconstruction	
   of	
   the	
   biomass	
  
for	
   liquid	
   fuel	
   production	
   has	
   recently	
   gained	
   a	
   lot	
   of	
   attention	
   as	
   one	
   of	
   the	
   ways	
   to	
  

64	
  
	
  

	
  
displace	
   fossil	
   derived	
   fuels.	
   To	
   this	
   end,	
   advances	
   have	
   been	
   made	
   in	
   pretreatment	
   and	
  
conversion	
   methods	
   aiming	
   to	
   efficiently	
   produce	
   fuels	
   from	
   biomass	
   and	
   biomass	
  
components.	
   Pretreatments	
   methods	
   offer	
   the	
   opportunity	
   to	
   release	
   and	
   fractionate	
   the	
  
components	
  of	
  biomass,	
  making	
  the	
  subsequent	
  conversion	
  processes	
  relatively	
  easier.1,2,3	
  
Usually	
   pretreatments	
   are	
   used	
   to	
   reduce	
   the	
   crystallinity	
   of	
   cellulose	
   and	
   remove	
   lignin	
  
and	
   hemicellulose	
   while	
   increasing	
   the	
   porosity	
   of	
   the	
   biomass	
   for	
   further	
   ease	
   of	
  
fractionation.	
  3,	
  4	
  
The	
   extractive	
   ammonia	
   pretreatment	
   (EAP)	
   improves	
   the	
   rates	
   and	
   extents	
   of	
  
subsequent	
   saccharification	
   by	
   separating	
   lignin	
   from	
   cellulose	
   and	
   hemicellulose	
   in	
   the	
  
conventional	
  biomass	
  to	
  ethanol	
  conversion	
  strategies.5	
  During	
  EAP,	
  ammonia	
  is	
  added	
  to	
  
biomass	
   at	
   moderate	
   pressure	
   (100	
   to	
   400	
   psi)	
   and	
   temperature	
   (70	
   to	
   200	
   °C).5	
   The	
  
pressure	
  is	
  then	
  rapidly	
  released;	
  this	
  rapid	
  depressurization	
  of	
  the	
  liquid	
  ammonia	
  causes	
  
the	
   biomass	
   fibers	
   to	
   expand	
   and	
   explode.3,	
   6	
   This	
   process	
   results	
   in	
   cellulose	
  
decrystallization,	
   hemicellulose	
   hydrolysis,	
   and	
   partial	
   lignin	
   depolymerization.5,7,8	
   The	
  
cellulose	
   and	
   hemicellulose	
   can	
   then	
   be	
   subjected	
   to	
   enzymatic	
   hydrolysis	
   for	
   ethanol	
  
production	
   while	
   lignin	
   streams	
   are	
   collected,	
   fractionated	
   and	
   extracted.	
   	
   These	
   lignin	
  
streams	
   are	
   partially	
   depolymerized	
   and	
   are	
   thus	
   lower	
   in	
   molecular	
   weight	
   than	
   the	
  
native	
   lignin	
   complex	
   found	
   in	
   biomass.	
   Lignin	
   monomers	
   and	
   oligomers	
   are	
   more	
  
amenable	
   to	
   chemical	
   transformation	
   to	
   higher	
   value	
   fuels	
   and	
   chemicals	
   and	
   are	
   thus	
  
better	
  feedstocks	
  than	
  native	
  lignin.	
  	
  	
  	
  
EAP	
   enables	
   lignin	
   recovery	
   via	
   variation	
   of	
   ammonia	
   loading,	
   residence	
   time,	
  
temperature	
  and	
  pressure.	
  Though	
  direct	
  combustion	
  of	
  lignin	
  is	
  an	
  option,	
  deriving	
  higher	
  
value	
  fuels	
  and	
  chemicals	
  is	
  desired	
  as	
  lignin	
  accounts	
  for	
  10-­‐30	
  wt%	
  of	
  biomass	
  and	
  40%	
  
65	
  
	
  

	
  
of	
   its	
   energy.9	
   The	
   production	
   of	
   lignin,	
   at	
   either	
   centralized	
   or	
   decentralized	
   facilities,	
  
provides	
  an	
  opportunity	
  for	
  thermal	
  and	
  electrocatalytic	
  approaches	
  to	
  produce	
  even	
  more	
  
liquid	
   fuel.	
   Fast	
   pyrolysis	
   is	
   one	
   such	
   thermochemical	
   approach	
   in	
   which	
   biomass	
   is	
  
liquefied	
  by	
  heating	
  in	
  the	
  absence	
  of	
  oxygen	
  to	
  form	
  pyrolysis	
  gas	
  and	
  biochar.	
  Most	
  of	
  the	
  
pyrolysis	
  gas	
  can	
  be	
  condensed	
  to	
  liquid	
  “bio-­‐oil”	
  with	
  a	
  bulk	
  density	
  greater	
  than	
  that	
  of	
  
the	
   feedstock.	
   Biomass	
   densification	
   near	
   the	
   harvest	
   source	
   reduces	
   the	
   cost	
   of	
  
transportation	
  and	
  storage	
  prior	
  to	
  upgrading	
  in	
  a	
  central	
  refinery.	
  
A	
   negative	
   aspect	
   of	
   fast	
   pyrolysis	
   is	
   that	
   bio-­‐oil’s	
   corrosiveness	
   and	
   reactive	
   instability	
  
pose	
   significant	
   barriers	
   to	
   the	
   adoption	
   of	
   pyrolysis	
   systems.10	
   Catalytic	
   stabilization	
   is	
  
needed	
   to	
   produce	
   a	
   stable	
   fuel	
   intermediate	
   that	
   is	
   compatible	
   with	
   common	
  
infrastructure	
  materials	
  such	
  as	
  carbon	
  steel.	
  Classical	
  catalytic	
  upgrading	
  is	
  usually	
  used	
  
to	
   hydrogenate	
   and	
   deoxygenate	
   bio-­‐oil,	
   a	
   process	
   that	
   occurs	
   at	
   high	
   temperature	
   and	
  
pressure.	
   These	
   severe	
   conditions	
   pose	
   significant	
   barriers,	
   such	
   as	
   catalyst	
   deactivation,	
  
for	
  bio-­‐oil	
  upgrading	
  in	
  decentralized	
  facilities.11	
  To	
  avoid	
  these	
  conditions,	
  electrocatalytic	
  
hydrogenation	
  (ECH)	
  is	
  proposed	
  to	
  stabilize	
  bio-­‐oil	
  under	
  mild	
  conditions	
  (25-­‐80	
  °C	
  and	
  1	
  
atm).	
  As	
  lignin	
  is	
  converted	
  to	
  phenolic	
  monomers,	
  dimers,	
  and	
  oligomers	
  upon	
  pyrolysis,	
  
the	
   transformation	
   of	
   model	
   compounds	
   exhibiting	
   similar	
   bonding	
   arrangements	
  
indicates	
  the	
  potential	
  for	
  the	
  ECH	
  of	
  biomass	
  lignin.	
  	
  
In	
   the	
   previous	
   chapter	
   we	
   were	
   able	
   to	
   demonstrate	
   successful	
   ECH	
   of	
   these	
   phenolic	
  
monomers	
  and	
  dimers	
  using	
  an	
  activated	
  carbon	
  cloth	
  supported	
  ruthenium	
  cathode.	
  As	
  a	
  
continuation	
   of	
   that	
   study	
   this	
   venture	
   attempts	
   to	
   establish	
   a	
   pyrolysis	
   protocol	
   for	
  
depolymerizing	
  EAP	
  lignin	
  with	
  heat	
  treatment	
  and	
  electrocatalytic	
  reduction	
  of	
  EAP	
  lignin.	
  	
  
Two	
   fractions	
   of	
   lignin	
   were	
   obtained	
   from	
   the	
   EAP	
   pretreatment	
   step.	
   The	
   composition	
   of	
  

66	
  
	
  

	
  
these	
   two	
   fractions	
   was	
   determined	
   using	
   elemental	
   analysis	
   and	
   characterized	
   using	
  
pyrolysis-­‐GC/MS,	
  thermogravimetric	
  analysis	
  and	
  bomb	
  calorimetry.	
  	
  The	
  results	
  of	
  these	
  
analyses	
   suggest	
   that	
   EAP	
   lignin	
   bio-­‐oil	
   can	
   be	
   successfully	
   stabilized	
   using	
   electrocatalytic	
  
treatment	
   at	
   small-­‐scale	
   depots	
   or	
   larger	
   biorefineries.	
   Furthermore,	
   as	
   a	
   continuation	
   of	
  
model	
   compound	
   ECH,	
   attempts	
   were	
   made	
   to	
   electrocatalytically	
   reduce	
   EAP	
   lignin	
   to	
  
smaller	
   fragments.	
   As	
   shown	
   in	
   Figure	
   3.1,	
   this	
   approach	
   uses	
   extracted	
   lignin	
   that	
   is	
   a	
  
byproduct	
   of	
   other	
   conversion	
   schemes,	
   thermochemical	
   conversion	
   to	
   bio-­‐oil	
   and	
  
upgrading	
   to	
   a	
   more	
   stable	
   form	
   at	
   a	
   decentralized	
   processing	
   depot	
   before	
   it	
   is	
  
transported	
  to	
  a	
  hydroprocessing	
  facility.	
  Hydroprocessing	
  may	
  be	
  unnecessary	
  depending	
  
upon	
  the	
  effectiveness	
  of	
  ECH.	
  	
  	
  

	
  
Figure	
  3.1:	
  Overall	
  project	
  scheme	
  from	
  biomass	
  harvesting	
  to	
  pretreatment	
  using	
  
extractive	
  ammonia	
  process	
  folowed	
  by	
  pyrolysis	
  and	
  electrocatalysis	
  to	
  upgrade	
  to	
  
valuable	
  procuscts	
  

67	
  
	
  

	
  
	
  
Experimental	
  Methods	
  
EAP	
  Lignin	
  Extraction	
  Method	
  	
  
EAP	
  lignin	
  was	
  obtained	
  from	
  Dr.	
  Bruce	
  Dale’s	
  lab.	
  The	
  extractive	
  ammonia	
  method	
  
used	
   for	
   extraction	
   of	
   lignin	
   as	
   provided	
   by	
   the	
   Dale	
   group,	
   is	
   represented	
   in	
   the	
   schematic	
  
in	
   Figure	
   3.2,	
   which	
   shows	
   the	
   extraction	
   process	
   and	
   the	
   resulting	
   molecular	
   weights	
   of	
  
EAP	
  product	
  streams.12	
  First,	
  corn	
  stover	
  was	
  oven	
  dried	
  at	
  60	
  °C	
  for	
  two	
  weeks,	
  milled	
  and	
  
stored	
  resulting	
  in	
  a	
  6	
  wt%	
  wet	
  basis	
  feed.	
  	
  This	
  feed	
  was	
  then	
  pretreated	
  in	
  1-­‐liter	
  high-­‐
pressure	
  stainless	
  steel	
  tubular	
  reactors.12	
  Each	
  reactor	
  contained	
  a	
  mixture	
  of	
  40	
  grams	
  of	
  
the	
  feed	
  with	
  240	
  grams	
  of	
  ammonia	
  for	
  30	
  minutes	
  at	
  120	
  °C	
  and	
  83	
  bar.12	
  As	
  the	
  system	
  
reached	
   the	
   set	
   point	
   temperature,	
   the	
   liquid	
   ammonia	
   and	
   soluble	
   extractives	
   were	
  
released	
   at	
   the	
   bottom	
   of	
   the	
   tank	
   while	
   the	
   ammonia	
   gas	
   was	
   released	
   from	
   the	
   top	
   of	
   the	
  
tank.	
  	
  The	
  biomass	
  left	
  in	
  the	
  tubular	
  reactors	
  was	
  then	
  removed	
  and	
  dried	
  overnight	
  in	
  the	
  
hood.	
  The	
  solid	
  part	
  was	
  subjected	
  to	
  enzymatic	
  hydrolysis	
  and	
  followed	
  by	
  extraction	
  via	
  
solvation	
  in	
  water.	
  For	
  the	
  liquid	
  fraction,	
  ethanol	
  was	
  used	
  to	
  collect	
  ethanol	
  soluble	
  and	
  
ethanol	
  insoluble	
  fractions.	
  All	
  of	
  fractions	
  were	
  then	
  resolubilised	
  in	
  water	
  to	
  extract	
  the	
  
water-­‐soluble	
  and	
  water-­‐insoluble	
  fractions.	
  	
  
This	
   fractionation	
   process	
   thus	
   yielded	
   four	
   separate	
   fractions:	
   ethanol	
  
insoluble/water-­‐insoluble	
  

(F1),	
  

ethanol	
  

insoluble/water-­‐soluble	
  

(F2),	
  

ethanol	
  

soluble/water-­‐insoluble	
   (F3)	
   (Figure	
   3.3),	
   and	
   ethanol	
   soluble/water-­‐soluble	
   (F4).	
  	
  
Characterization	
   of	
   both	
   the	
   F1	
   and	
   F3	
   EAP	
   lignin	
   fractions	
   involved	
   py-­‐GC/MS,	
   TGA	
   and	
  

68	
  
	
  

	
  
bomb	
  calorimetry.	
  	
  Ultimate	
  analysis	
  was	
  also	
  conducted	
  to	
  directly	
  quantify	
  the	
  amount	
  of	
  
elemental	
  carbon,	
  hydrogen,	
  nitrogen	
  and	
  sulfur	
  and	
  indirectly,	
  oxygen	
  by	
  difference.	
  	
  

Conrn	
  Stover	
  	
  
(100	
  g	
  total	
  lignin)	
  

Untreated	
  Biomass	
  

Liquid	
  
(44	
  g	
  lignin)	
  

EAP	
  (6:1	
  ammonia:biomass)	
  
(120	
  °C,	
  83	
  bar)	
  

Extraction/Hydrolysis	
  	
  

Ethanol	
  Insoluble	
  	
  

Solid	
  
(56	
  g	
  lignin)	
  

Ethanol	
  Soluble	
  

Enzymatic	
  Hydrolysis	
  
(EH)	
  

%	
  Total	
  Lignin	
  	
  

F1	
  	
  	
  	
  	
  
Water	
  
Insoluble	
  

F2	
  	
  	
  	
  
Water	
  
Soluble	
  	
  

F3	
  	
  	
  	
  
Water	
  
Insoluble	
  	
  

	
  F4	
  	
  	
  
Water	
  
Soluble	
  	
  

F5	
  	
  	
  
	
  Water	
  
Insoluble	
  	
  

F6	
  	
  	
  	
  
Water	
  
Soluble	
  	
  

%	
  Lignin	
  in	
  Sample	
  	
  

69.1%	
  	
  
(1	
  g)	
  

14.4%	
  
(3	
  g)	
  

92.4%	
  
	
  (32	
  g)	
  

13.5%	
  
(8	
  g)	
  

42.9%	
  
(51	
  g)	
  

EH	
  
(5g)	
  

Molecular	
  	
  
Weight	
  (GPC)	
  	
  

3314	
  
(g/mol)	
  

2880	
  
(g/mol)	
  

1470	
  
(g/mol)	
  

416	
  
(g/mol)	
  

4140	
  
(g/mol)	
  

~	
  

	
  
Figure	
  3.2:	
  Method	
  used	
  to	
  produce	
  EAP	
  lignins.	
  	
  Lignins	
  are	
  present	
  in	
  oligomeric	
  and	
  
polymeric	
  forms	
  as	
  per	
  the	
  molecular	
  weights	
  of	
  each	
  fraction.	
  

69	
  
	
  

	
  

	
  
Figure	
  3.3:	
  Ethanol	
  soluble	
  F3	
  fraction	
  as	
  obtained	
  from	
  liquid	
  ammonia	
  after	
  precipication	
  
in	
  water	
  followed	
  by	
  solubilization	
  in	
  ethanol	
  
Higher	
  Heating	
  Value	
  (Bomb	
  Calorimetry)	
  	
  
Bomb	
  calorimetry	
  was	
  used	
  to	
  determine	
  the	
  higher	
  heating	
  value	
  (HHV)	
  of	
  the	
  two	
  
fractions	
  using	
  a	
  Parr	
  Plain	
  Jacket	
  Calorimeter	
  (Parr	
  Intruments	
  Co.,Molin,	
  IL).	
  Samples	
  of	
  
about	
  110	
  mg	
  of	
  both	
  fractions	
  were	
  mixed	
  with	
  10-­‐14	
  mg	
  of	
  dodecane	
  and	
  combusted	
  to	
  
determine	
  the	
  higher	
  heating	
  value.	
  	
  
Elemental	
  Analysis	
  (CHNS)	
  
C,	
   H,	
   N,	
   S	
   data	
   was	
   obtained	
   using	
   combustion	
   with	
   automatic	
   analyzer	
   from	
   the	
  
Atlantic	
   Microlabs	
   (Norcross,	
   GA)	
   .	
   Oxygen	
   was	
   calculated	
   by	
   difference.	
   The	
   samples	
   were	
  
not	
  dried	
  prior	
  to	
  analysis.	
  	
  

70	
  
	
  

	
  
Thermogravimatric	
  Analysis	
  (TGA)	
  	
  
TGA	
  analysis	
  was	
  performed	
  on	
  both	
  the	
  lignin	
  components.	
  Several	
  grams	
  of	
  each	
  
sample	
   were	
   introduced	
   to	
   the	
   TGA.	
   Initially	
   the	
   temperature	
   was	
   held	
   at	
   30	
   °C	
   for	
   10	
  
minutes,	
   then	
   the	
   temperature	
   was	
   increased	
   to	
   104	
   °C	
   at	
   a	
   rate	
   of	
   10	
   K/min,	
   this	
  
temperature	
   was	
   held	
   for	
   10	
   minutes,	
   and	
   finally	
   increased	
   to	
   800	
   °C	
   at	
   10	
   K/min.	
   	
   The	
  
mass	
   loss	
   curve	
   and	
   its	
   derivative	
   were	
   plotted	
   to	
   identify	
   those	
   temperatures	
   that	
  
correspond	
  to	
  key	
  thermal	
  events,	
  such	
  as	
  water	
  loss,	
  hemicellulose	
  degradation	
  or	
  lignin	
  
degradation.	
  	
  	
  
Pyrolysis	
  GC/MS	
  
Py-­‐GC/MS	
  analysis	
  of	
  both	
  F1	
  and	
  F3	
  fractions	
  was	
  performed	
  using	
  a	
  micro	
  scale	
  
pyrolysis	
   unit	
   (CDS	
   pyroprobe	
   5250,	
   CDC	
   Analytical	
   inc.	
   Oxford,	
   PA)	
   coupled	
   with	
   a	
  
Shimadzu	
   QP_5050A	
   GC/MS	
   (Shimadzu	
   Corp.	
   Columbia,	
   MD).	
   Several	
   micrograms	
   of	
   the	
  
lignin	
   fraction	
   were	
   packed	
   in	
   a	
   quartz	
   tube	
   between	
   quartz	
   wool	
   plugs	
   and	
   subjected	
   to	
  
py-­‐GC/MS.	
  The	
  pyroprobe	
  was	
  set	
  to	
  600	
  °C	
  and	
  held	
  there	
  for	
  10	
  seconds	
  with	
  a	
  transfer	
  
line	
   temp	
   of	
   300	
   °C.	
   The	
   GC	
   used	
   a	
   Restek	
   RTX-­‐1701	
   column	
   of	
   60m	
   length,	
   0.25	
   mm	
  
diameter	
   and	
   0.25	
   µm	
   thickness.	
   (Restek,	
   Bellefonte,	
   PA).	
   The	
   GC	
   program	
   was	
   set	
   at	
   40	
   °C	
  
with	
   a	
   1	
   minute	
   hold	
   time,	
   followed	
   by	
   an	
   8	
   °C/min	
   ramp	
   to	
   270	
   °C	
   with	
   a	
   10	
   minute	
   hold.	
  
The	
  injection	
  and	
  interface	
  temperature	
  were	
  set	
  at	
  280	
  °C.	
  	
  A	
  split	
  injection	
  with	
  a	
  1:100	
  
split	
   ratio	
   was	
   used.	
   	
   Helium	
   flow	
   through	
   the	
   column	
   was	
   maintained	
   at	
   1	
   ml/min.	
   The	
  
mass	
  spectra	
  were	
  collected	
  in	
  electron	
  ionization	
  mode	
  with	
  the	
  mass-­‐to-­‐charge	
  ratio	
  set	
  
to	
   range	
   from	
   33	
   to	
   300.	
   Compounds	
   were	
   identified	
   by	
   comparison	
   of	
   the	
   mass	
   spectra	
   of	
  

71	
  
	
  

	
  
the	
  major	
  peaks	
  with	
  the	
  National	
  Institute	
  of	
  Standards	
  and	
  Technology	
  (NIST)	
  library	
  to	
  
obtain	
  the	
  best	
  possible	
  matches.	
  	
  
Catalyst	
  Preparation	
  
Zorflex	
   ACC	
   (activated	
   carbon	
   cloth)	
   FM	
   100	
   was	
   used	
   to	
   support	
   the	
   ruthenium	
  
catalyst.	
   As	
   described	
   by	
   Li	
   et.	
   al.,13	
   the	
   activated	
   carbon	
   cloth	
   was	
   washed	
   overnight	
   in	
  
deionized	
   water	
   and	
   oven	
   dried	
   at	
   105	
   °C.	
   The	
   ACC	
   support	
   was	
   prepared	
   with	
   catalyst	
  
using	
   the	
   incipient	
   wetness	
   method	
   as	
   described	
   by	
   Li	
   et.	
   al.13	
   Ru(NH3)6Cl3	
   solution	
   was	
  
used	
  to	
  soak	
  each	
  1.5	
  x	
  3.0	
  cm	
  piece	
  of	
  ACC.	
  Each	
  cloth	
  was	
  immersed	
  in	
  the	
  solution	
  and	
  
soaked	
  for	
  a	
  few	
  minutes.	
  The	
  Ru/ACC	
  catalyst	
  was	
  then	
  dried	
  at	
  room	
  temperature	
  first	
  
overnight	
   and	
   stored	
   in	
   a	
   vacuum	
   dessicator	
   for	
   another	
   24	
   hours	
   then	
   reduced	
   with	
  
molecular	
  hydrogen	
  at	
  500	
  psi	
  and	
  310	
  °C	
  for	
  12	
  hours	
  in	
  a	
  Parr	
  reactor	
  (model	
  452HC).	
  	
  	
  
Electrocatalytic	
  Hydrogenation	
  of	
  EAP	
  Lignin	
  	
  
Electrocatalysis	
   of	
   the	
   F3	
   fraction	
   was	
   performed	
   in	
   a	
   two-­‐chambered	
  
electrochemical	
   glass	
   H-­‐cell	
   separated	
   by	
   a	
   Dupont	
   Nafion-­‐117	
   membrane.	
   Ruthenium	
  
supported	
  on	
  activated	
  carbon	
  cloth	
  (Ru/ACC)	
  was	
  used	
  as	
  the	
  cathode	
  and	
  platinum	
  wire	
  
was	
   used	
   as	
   the	
   anode	
   as	
   shown	
   in	
   Figure	
   3.4.	
   A	
   constant	
   temperature	
   of	
   80	
   °C	
   was	
  
maintained	
  by	
  placing	
  the	
  whole	
  cell	
  in	
  a	
  heated	
  silicon	
  oil	
  bath.	
  	
  An	
  Instek	
  GPR-­‐11H30D	
  
power	
   supply	
   was	
   used	
   to	
   provide	
   constant	
   current.	
   1M	
   NaOH	
   was	
   used	
   as	
   the	
   electrolyte.	
  
After	
   cell	
   setup	
   was	
   completed,	
   a	
   10	
   min	
   pre-­‐electrolysis	
   step	
   was	
   performed	
   on	
   the	
  
catalyst	
  at	
  80mA	
  before	
  adding	
  the	
  substrate.	
  After	
  pre-­‐electrolysis,	
  0.045	
  gm	
  of	
  substrate	
  

72	
  
	
  

	
  
was	
   added	
   and	
   the	
   experiment	
   was	
   run	
   at	
   80°C	
   and	
   80mA	
   for	
   27	
   hours.	
   Samples	
   (1	
   ml)	
  
were	
  taken	
  at	
  12,	
  24,	
  26	
  and	
  27	
  hours.	
  

	
  
Figure	
  3.4:	
  Two	
  chambered	
  H-­‐cell	
  setup	
  
Size	
  Exclusion	
  Chromatography	
  
	
  Samples	
   (0.25	
   ml)	
   were	
   taken	
   and	
   diluted	
   using	
   the	
   SEC's	
   mobile	
   phase	
   (0.1	
   M	
  
NaNO3	
   0.01	
   M	
   NaOH)	
   and	
   analyzed	
   using	
   an	
   Agilent	
   1100	
   HPLC	
   fitted	
   with	
   a	
   Waters	
  
UltrahydrogelTM	
   250	
   7.8	
   x	
   300mm	
   column.	
   Both	
   diode	
   array	
   (DAD)	
   and	
   refractive	
   index	
  
detectors	
  were	
  utilized.	
  A	
  flow	
  rate	
  of	
  1	
  ml/min	
  was	
  used	
  with	
  20	
  µl	
  injection	
  volume	
  and	
  a	
  
column	
  temperature	
  of	
  35	
  °C.	
  As	
  lignin	
  standards	
  were	
  not	
  available	
  the	
  molecular	
  weight	
  
distribution	
   was	
   not	
   determined.	
   The	
   intensity	
   of	
   the	
   detector	
   signal	
   vs.	
   the	
   elution	
   time	
  
was	
   plotted	
   with	
   larger	
   molecules	
   assumed	
   to	
   elute	
   first	
   followed	
   by	
   smaller	
   molecules	
  
eluting	
  out	
  later.	
  The	
  remainder	
  of	
  each	
  sample	
  was	
  then	
  saturated	
  with	
  NaCl	
  acidified	
  to	
  
pH	
   1	
   and	
   extracted	
   using	
   chloroform	
   for	
   analysis	
   using	
   GC/MS	
   to	
   identify	
   any	
  
depolymerization	
  products.	
  The	
  catalyst	
  was	
  placed	
  in	
  5	
  ml	
  of	
  chloroform,	
  sonicated	
  for	
  10	
  
minutes,	
  and	
  filtered	
  prior	
  to	
  analysis	
  by	
  GC/MS.	
  	
  

73	
  
	
  

	
  
Results	
  and	
  Discussion	
  	
  
HHV,	
  Elemental	
  Analysis	
  and	
  TGA	
  
The	
  reported	
  values	
  for	
  the	
  higher	
  heating	
  value	
  of	
  biomass	
  is	
  12-­‐19	
  MJ/Kg	
  and	
  bio-­‐
oil	
   is	
   16-­‐19	
   MJ/Kg14.	
   Calorimetery	
   yielded	
   a	
   higher	
   heating	
   value	
   of	
   30.12	
   MJ/Kg	
   for	
   the	
  
low	
  molecular	
  weight	
  lignin	
  (F3)	
  and	
  21.20	
  MJ/Kg	
  for	
  the	
  high	
  molecular	
  weight	
  lignin	
  (F1)	
  
as	
  shown	
  in	
  Table	
  3.3.	
  	
  As	
  expected,	
  the	
  HHV	
  values	
  for	
  the	
  F1	
  and	
  F3	
  fractions	
  are	
  higher	
  
than	
  those	
  of	
  the	
  parent	
  corn	
  stover.	
  	
  	
  
The	
   F3	
   fraction	
   elemental	
   analysis	
   revealed	
   the	
   levels	
   of	
   oxygen	
   present	
   in	
   this	
  
lignin	
   fraction.	
   	
   Bio-­‐oil	
   tends	
   to	
   retain	
   most	
   of	
   the	
   oxygen	
   that	
   is	
   present	
   in	
   the	
   parent	
  
biomass,	
  which	
  could	
  be	
  up	
  to	
  35-­‐60	
  wt%.15	
  The	
  presence	
  of	
  such	
  a	
  large	
  amount	
  of	
  oxygen	
  
in	
   bio-­‐oil	
   is	
   the	
   main	
   reason	
   for	
   the	
   vast	
   differences	
   in	
   properties	
   between	
   bio-­‐oil	
   and	
  
conventional	
  fuel	
  oil.16	
  Such	
  undesirable	
  properties	
  as	
  low	
  energy	
  content10;	
  instability	
  in	
  
storage	
  due	
  to	
  high	
  reactivity17;	
  immiscibility	
  with	
  non-­‐polar	
  petroleum	
  fuels10	
  etc.	
  are	
  all	
  
properties	
   that	
   can	
   be	
   attributed	
   to	
   high	
   oxygen	
   content.	
   Furthermore,	
   high	
   reactivity	
  
results	
  in	
  the	
  formation	
  of	
  additional	
  water	
  as	
  a	
  side	
  product,	
  which	
  affects	
  the	
  combustion	
  
properties	
  of	
  the	
  fuel.	
  	
  As	
  can	
  be	
  seen	
  from	
  the	
  elemental	
  analysis	
  results	
  in	
  Table	
  3.1,	
  the	
  
F3	
   fraction	
   has	
   less	
   oxygen	
   than	
   reported	
   oxygen	
   values	
   for	
   biomass-­‐derived	
   bio-­‐oil.	
  
Pyrolysis	
   coupled	
   with	
   electrocatalysis	
   can	
   further	
   help	
   reduce	
   the	
   amount	
   of	
   oxygen	
  
resulting	
  in	
  a	
  higher	
  energy	
  content	
  fuel.	
  
	
  
	
  
	
  

74	
  
	
  

	
  
Table	
  3.1:	
  HHV	
  and	
  elemental	
  analysis	
  of	
  F3	
  and	
  F1	
  fraction	
  
	
  

HHV	
  
(MJ/Kg)*	
  

C	
  

H	
  

N	
  

S	
  

F3	
  

30.12	
  

65.68	
  

8.13	
  

2.62	
  

0.0	
  

23.57	
  

F1	
  

21.20	
  

44.36	
  

5.43	
  

3.78	
  

0.19	
  

46.24	
  

	
  

O	
  	
  
(By	
  difference)	
  

	
  
	
  
	
  

	
  
The	
  DTG	
  curves	
  for	
  the	
  F3	
  and	
  F1	
  fractions	
  were	
  obtained	
  by	
  differentiating	
  the	
  TGA	
  
curve	
   for	
   both	
   fractions.	
   The	
   results	
   reveal	
   that	
   there	
   is	
   a	
   major	
   thermal	
   event	
   at	
   354	
   °C	
  
(refer	
   to	
   Figure	
   3.5	
   and	
   3.6).	
   The	
   DTG	
   curve	
   of	
   the	
   F3	
   fraction	
   (Figure	
   3.5)	
   stretches	
   over	
   a	
  
large	
  range,	
  which	
  is	
  typical	
  of	
  lignin	
  thermal	
  degradation.	
  The	
  F3	
  DTG	
  curve	
  shows	
  typical	
  
characteristics	
   of	
   lignin	
   DTG	
   curves	
   found	
   in	
   the	
   literature.	
   If	
   it	
   were	
   to	
   be	
   compared	
   to	
  
cellulose	
  or	
  hemicellulose	
  DTG	
  curves,	
  it	
  would	
  be	
  noted	
  that	
  this	
  lignin	
  DTG	
  curve	
  is	
  a	
  lot	
  
less	
   sharp.	
   This	
   can	
   be	
   attributed	
   to	
   the	
   inhomogeneous	
   nature	
   of	
   the	
   lignin	
   polymer.	
  	
  
Unlike	
  hemicellulose	
  and	
  cellulose,	
  which	
  are	
   relatively	
   homogeneous	
   polymers	
   composed	
  
of	
  simple	
  sugars	
  that	
  decompose	
  at	
  a	
  high	
  rate	
  within	
  a	
  narrow	
  temperature	
  range,18	
  lignin	
  
is	
   composed	
   of	
   monolignols	
   that	
   form	
   complex	
   and	
   diverse	
   cross	
   linkages	
   that	
   make	
   it	
  
more	
  resistant	
  to	
  thermal	
  degradation.9,	
   19	
   	
  This	
  gives	
  lignin	
  a	
  wide	
  range	
  of	
  temperatures	
  
over	
   which	
   it	
   undergoes	
   thermal	
   decomposition.	
   The	
   F1	
   fraction	
   in	
   comparison	
   shows	
   a	
  
sharper	
   DTG	
   peak	
   as	
   compared	
   to	
   the	
   F3	
   curve.	
   As	
   compared	
   to	
   DTG	
   curves	
   in	
   the	
  
literature20	
   this	
   curve	
   suggests	
   that	
   the	
   F1	
   lignin	
   might	
   contain	
   some	
   cellulose	
   residues.	
  	
  
The	
   sharpness	
   of	
   the	
   DTG	
   peak	
   for	
   this	
   particular	
   fraction	
   could	
   be	
   indicative	
   of	
   residual	
  
cellulose	
  and	
  hemicellulose	
  from	
  the	
  extraction	
  process.	
  	
  	
  

75	
  
	
  

	
  
TGA	
  =	
  mass	
  loss	
  with	
  increasing	
  temperature	
  	
  
DTG	
  =	
  rate	
  of	
  mass	
  loss	
  per	
  increase	
  in	
  temperature	
  	
  

0.025	
  

7	
  

0.020	
  

6	
  
0.015	
  

	
  TGA	
  (mg)	
  

5	
  
4	
  

0.010	
  

3	
  

0.005	
  

2	
  
0.000	
  

1	
  
0	
  
104	
  

DTG	
  (mass	
  in	
  mg/°C)	
  

8	
  

-­‐0.005	
  
154	
  

204	
  

254	
  

304	
  

354	
  

404	
  

454	
  

504	
  

554	
  

Temperature(°C)	
  

	
  

Figure	
  3.5:	
  TGA	
  analysis	
  of	
  F3	
  fraction	
  
	
  	
  	
  	
  	
  
0.053	
  

TGA	
  =	
  mass	
  loss	
  with	
  increasing	
  temperature	
  	
  
DTG	
  =	
  rate	
  of	
  mass	
  loss	
  per	
  increase	
  in	
  temperature	
  	
  

0.045	
  

10	
  

0.038	
  

TGA	
  (mg)	
  

8	
  

0.030	
  

6	
  

0.023	
  

4	
  

0.015	
  

2	
  

DTG	
  (mg/°C)	
  

12	
  

0.008	
  

0	
  

0.000	
  

104	
  

154	
  

204	
  

254	
  

304	
  

354	
  

404	
  

454	
  

504	
  

Temperature(°C)	
  

Figure	
  3.6:	
  TGA	
  analysis	
  of	
  F1	
  fraction	
  

554	
  

	
  

Although	
  TGA	
  and	
  DTG	
  curve	
  provide	
  a	
  representation	
  of	
  the	
  thermal	
  degradation	
  
temperature	
   of	
   lignin,	
   the	
   heating	
   rates	
   employed	
   in	
   thermogravimetric	
   analysis	
   are	
   far	
  
from	
   the	
   heating	
   rates	
   the	
   lignin	
   will	
   experience	
   in	
   a	
   typical	
   pyrolysis	
   reactor	
   which	
   can	
  
approach	
  rates	
  of	
  300-­‐1000	
  °C/s.20	
  In	
  addition	
  to	
  not	
  being	
  able	
  to	
  provide	
  realistic	
  heating	
  
values	
  for	
  fast	
  pyrolysis,	
  TGA	
  studies	
  fall	
  short	
  due	
  to	
  their	
  inability	
  to	
  provide	
  information	
  

76	
  
	
  

	
  
about	
   what	
   compounds	
   are	
   being	
   formed	
   during	
   the	
   thermal	
   degradation	
   process.21	
  
However,	
  the	
  TGA	
  data	
  obatiend	
  in	
  this	
  study	
  provides	
  relevant	
  guidlines	
  for	
  setting	
  up	
  a	
  
protocol	
  for	
  pyrolysis	
  of	
  EAP	
  lignin	
  using	
  large-­‐scale	
  pyrolysis	
  screw	
  conveyor	
  reactor.	
  	
  
Pyrolysis	
  GC/MS	
  
The	
   major	
   peaks	
   obtained	
   in	
   the	
   case	
   of	
   the	
   F3	
   fraction	
   were	
   consistent	
   with	
   the	
  
compounds	
   that	
   are	
   expected	
   from	
   lignin	
   pyrolysis,	
   as	
   shown	
   in	
   Figure	
   3.7.	
   The	
   lack	
   of	
   any	
  
peaks	
  typical	
  of	
  carbohydrate	
  pyrolysis	
  such	
  as	
  C2-­‐C4	
  aldehydes	
  and	
  ketones,	
  levoglucosan	
  
or	
  furans	
  and	
  the	
  presence	
  of	
  large	
  amounts	
  of	
  phenols	
  such	
  as	
  phenol,	
  guaiacol,	
  creosol,	
  4-­‐
ethylguaiacol,	
   syringol,	
   4-­‐vinylphenol,	
   etc,	
   support	
   the	
   purity	
   of	
   this	
   lignin	
   fraction.	
   Since	
  
plant-­‐derived	
   phenols	
   are	
   considered	
   to	
   have	
   relevance	
   as	
   they	
   have	
   a	
   potential	
   to	
   replace	
  
petroleum-­‐based	
  phenols	
  which	
  are	
  often	
  high	
  in	
  cost,	
  22	
  conversion	
  of	
  these	
  lignin	
  fraction	
  
to	
   phenolic	
   monomers	
   via	
   fast	
   pyrolysis	
   will	
   be	
   beneficial.	
   However,	
   further	
   studies	
   should	
  
be	
   conducted	
   to	
   determine	
   the	
   yields	
   of	
   products	
   from	
   EAP	
   lignin	
   pyrolysis	
   to	
   assess	
   the	
  
potential	
  of	
  this	
  method	
  to	
  produce	
  liquid	
  fuels.	
  	
  

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Figure	
  3.7:	
  Py/GC	
  chromatogram	
  of	
  F3	
  fraction	
  with	
  peak	
  labels	
  outlined	
  in	
  Table	
  3.2	
  
	
  
77	
  
	
  

	
  
Table	
  3.2:	
  Retention	
  times	
  of	
  products	
  from	
  Py/GC-­‐MS	
  of	
  F3	
  fraction	
  
#	
  
Compound	
  Name	
  
Retention	
  time	
  (min)	
  
1	
  

Unidentified	
  

3.633	
  

2	
  

Carbon	
  Dioxide	
  

3.89	
  

3	
  

Phenol	
  

16.294	
  

4	
  

Guaiacol	
  

16.802	
  

5	
  

3-­‐Methylphenol	
  

17.994	
  

6	
  

Creosol	
  

18.833	
  

7	
  

3-­‐Ethylphenol	
  

19.673	
  

8	
  

4-­‐Ethylguaiacol	
  

20.418	
  

9	
  

4-­‐Vinylphenol	
  

21.266	
  

10	
  

4-­‐Vinylguaiacol	
  

21.497	
  

11	
  

Syringol	
  

22.394	
  

12	
  

Isoeugenol	
  	
  

23.81	
  

13	
  

1,2,4-­‐Trimethoxybenzene	
  

23.945	
  

14	
  

2-­‐Butyl-­‐1,1,3-­‐trimethylcyclohexane	
  

25.144	
  

15	
  

3-­‐Tert-­‐butyl-­‐4-­‐hydroxyanisole	
  

26.099	
  

16	
  

Phenol,	
  2,6-­‐Dimethoxy-­‐4-­‐(2-­‐propenyl)-­‐	
  

28.071	
  

Electrocatalytic	
  Hydrogenation	
  of	
  EAP	
  Lignin	
  	
  
In	
   an	
   effort	
   to	
   stabilize	
   lignin-­‐derived	
   bio-­‐oil,	
   electrocatalytic	
   hydrogenation	
   was	
  
employed.	
   Several	
   lignin	
   model	
   compounds	
   were	
   chosen	
   for	
   electrocatalytic	
   reduction.	
  	
  
Previous	
   work	
  as	
  detailed	
  in	
  Chapter	
  2	
  showed	
  that	
  both	
  monomeric	
  and	
  dimeric	
  lignins	
  
are	
   reduced	
   to	
   such	
   products	
   as	
   alkoxycyclohexanols,	
   phenol	
   and	
   cyclohexanol.	
   This	
  
demonstrates	
   that	
   Ru/ACC	
   catalyst	
   can	
   be	
   effective	
   in	
   reducing	
   lignin-­‐derived	
   model	
  
compounds.	
  	
  Instead	
  of	
  model	
  compounds,	
  EAP	
  lignin	
  is	
  used	
  to	
  extend	
  the	
  results	
  of	
  model	
  
compounds	
   studies	
   to	
   an	
   authentic	
   biomass	
   stream.	
   As	
   EAP	
   lignin	
   has	
   high	
   molecular	
  
weight,	
  some	
  form	
  of	
  depolymerization	
  is	
  necessary.	
  	
  Though	
  fast	
  pyrolysis	
  may	
  be	
  used	
  to	
  
78	
  
	
  

	
  
reduce	
  molecular	
  weight,	
  the	
  direct	
  ECH	
  of	
  EAP	
  lignin	
  was	
  studied	
  to	
  gauge	
  the	
  extent	
  of	
  
depolymerization	
   achieved	
   through	
   electroreduction.	
   	
   To	
   achieve	
   these	
   goals,	
  
electrocatalysis	
  of	
  EAP	
  lignin	
  was	
  also	
  performed	
  Ru/ACC	
  catalyst	
  at	
  80°C	
  and	
  80mA	
  for	
  27	
  
hours.	
   	
   As	
   the	
   F3	
   EAP	
   fraction	
   is	
   insoluble	
   in	
   water	
   but	
   soluble	
   in	
   basic	
   conditions,	
   1M	
  
NaOH	
  was	
  used	
  as	
  an	
  electrolyte	
  in	
  the	
  ECH	
  study.	
  During	
  the	
  experiment	
  it	
  was	
  observed	
  
that	
  there	
  was	
  an	
  increase	
  in	
  voltage	
  around	
  the	
  12-­‐hours	
  and	
  a	
  further	
  rapid	
  increase	
  in	
  
voltage	
   after	
   the	
   26	
   hours.	
   	
   This	
   could	
   suggest	
   that	
   due	
   to	
   the	
   basic	
   conditions	
   of	
   the	
  
electrolyte	
   solution	
   and	
   the	
   presence	
   of	
   oxgyen,	
   polymerization	
   of	
   the	
   lignin	
   oligomers	
  
might	
  have	
  occurred.	
  The	
  sudden	
  jump	
  in	
  voltage	
  indicates	
  polymer	
  formation	
  around	
  26	
  
hours,	
   which	
   results	
   in	
   decreased	
   conductivity	
   because	
   of	
   blockage	
   on	
   the	
   catalyst	
   surface.	
  
Under	
  galvanostatic	
  control,	
  the	
  voltage	
  increases	
  to	
  maintain	
  the	
  desired	
  current.	
  As	
  the	
  
voltage	
   exceeded	
   100	
   volts,	
   the	
   experiment	
   was	
   stopped	
   after	
   27	
   hours.	
   Samples	
   were	
  
taken	
   periodically	
   for	
   further	
   GPC	
   analysis	
   but	
   the	
   results	
   were	
   inconclusive.	
   Further	
  
analysis	
  of	
  the	
  samples	
  using	
  GC/MS	
  did	
  not	
  show	
  any	
  chromatographic	
  peaks,	
  which	
  could	
  
indicate	
   a	
   lack	
   of	
   analytes	
   between	
   mass	
   to	
   charge	
   ratios	
   from	
   30	
   to	
   300.	
   	
   As	
   such,	
   the	
  
products	
  have	
  molecular	
  too	
  large	
  to	
  be	
  detected	
  by	
  the	
  GC/MS	
  method	
  employed.	
  	
  In	
  lieu	
  
of	
   basic	
   conditions,	
   acidic	
   and	
   neutral	
   conditions	
   could	
   be	
   explored	
   in	
   the	
   cathode	
  
compartment	
   of	
   ECH	
   to	
   enhance	
   depolymerization.	
   	
   Further,	
   the	
   use	
   of	
   pyrolysis	
   or	
  
perhaps	
   oxidative	
   approaches	
   may	
   be	
   needed	
   to	
   create	
   low	
   molecular	
   weight	
   reactants	
   for	
  
reduction	
  by	
  ECH.	
  
Conclusion	
  	
  
	
  

As	
   one	
   of	
   the	
   components	
   of	
   biomass	
   and	
   a	
   component	
   responsible	
   for	
   a	
   large	
  

fraction	
   of	
   the	
   energy	
   stored	
   in	
   biomass,	
   lignin	
   has	
   great	
   potential	
   for	
   hydrocarbon	
   fuel	
  
79	
  
	
  

	
  
production.	
  However	
  in	
  today’s	
  biofuel	
  production	
  efforts	
  lignin	
  is	
  often	
  a	
  by-­‐product	
  that	
  
is	
   not	
   being	
   utilized	
   efficiently	
   due	
   to	
   the	
   lack	
   of	
   efficient	
   depolymerization	
   schemes	
   for	
  
lignin	
   conversion	
   to	
   fuels	
   or	
   value-­‐added	
   commodities.	
   Processes	
   such	
   as	
   fast	
   pyrolysis	
  
could	
   prove	
   very	
   beneficial	
   in	
   solving	
   this	
   problem.	
   In	
   this	
   study,	
   the	
   main	
   reason	
   for	
  
characterizing	
  the	
  EAP	
  lignin	
  was	
  to	
  determine	
  its	
  potential	
  as	
  a	
  possible	
  feed	
  material	
  for	
  
fast	
  pyrolysis	
  and	
  subsequent	
  ECH.	
  	
  These	
  characterization	
  results	
  give	
  a	
  certain	
  amount	
  of	
  
insight	
   towards	
   setting	
   up	
   a	
   lignin	
   depolymerization	
   scheme	
   using	
   fast	
   pyrolysis	
   coupled	
  
with	
  electrocatalysis.	
  	
  The	
  results	
  are	
  summarized	
  below.	
  	
  
o Higher	
   heating	
   value	
   and	
   elemental	
   analysis:	
   these	
   results	
   indicated	
   that	
   the	
   F3	
  
fraction	
  had	
  a	
  larger	
  heating	
  value	
  and	
  less	
  oxygen	
  then	
  F1,	
  potentially	
  making	
  it	
  a	
  
better	
   feed	
   material.	
   As	
   pyrolysis	
   oils	
   tend	
   to	
   retain	
   most	
   of	
   the	
   oxygen	
   from	
   the	
  
feed	
   material,	
   having	
   a	
   lignin	
   fraction	
   with	
   less	
   oxygen	
   to	
   begin	
   with	
   makes	
   it	
   a	
  
more	
  desirable	
  feed.	
  	
  
o Thermogravimetric	
   analysis:	
   TGA/DTG	
   curves	
   for	
   both	
   fractions	
   indicate	
   that	
   the	
  
decomposition	
   of	
   lignin	
   occurred	
   over	
   a	
   wide	
   range	
   of	
   temperatures	
   with	
   a	
   major	
  
thermal	
   event	
   occurring	
   at	
   around	
   345	
   °C.	
   This	
   gives	
   us	
   an	
   idea	
   of	
   what	
  
temperatures	
   to	
   explore	
   when	
   implementing	
   pyrolyis	
   of	
   these	
   fractions	
   at	
   a	
   large	
  
scale.	
   	
   But	
   it	
   is	
   important	
   to	
   note	
   that	
   heating	
   rates	
   applied	
   during	
   TGA	
   analysis	
   are	
  
much	
  lower	
  than	
  those	
  of	
  an	
  actual	
  fast	
  pyrolysis	
  reactor.	
  TGA	
  results,	
  though	
  useful	
  
for	
  setting	
  pilot-­‐scale	
  reactor	
  operating	
  temperatures,	
  should	
  not	
  be	
  relied	
  upon	
  as	
  a	
  
scale-­‐up	
   criterion,	
   i.e.	
   the	
   results	
   of	
   slow	
   pyrolysis	
   will	
   differ	
   from	
   fast	
   pyrolysis.	
  	
  	
  
Additionally	
   it	
   was	
   noted	
   that	
   the	
   F3	
   fraction	
   showed	
   a	
   DTG	
   curve	
   typical	
   of	
   pure	
  
lignin	
   samples	
   while	
   F1	
   showed	
   a	
   DTG	
   curve	
   typical	
   of	
   samples	
   with	
   residual	
  
80	
  
	
  

	
  
cellulose	
   and	
   hemicelluose.	
   Thus,	
   F3	
   will	
   probably	
   be	
   a	
   better	
   feed	
   material	
   if	
   the	
  
target	
  is	
  to	
  pyrolyze	
  lignin	
  rich	
  feedstock.	
  	
  
o Pyrolysis	
   GC/MS:	
   these	
   results	
   gave	
   a	
   very	
   good	
   indication	
   of	
   what	
   the	
   pyrolysis	
  
products	
   of	
   the	
   F3	
   fraction	
   might	
   look	
   like	
   at	
   temperatures	
   close	
   to	
   600	
   °C.	
  
However,	
   further	
   py-­‐GC/MS	
   experiments	
   should	
   be	
   conducted	
   to	
   quantify	
   the	
  
overall	
  yields	
  of	
  molecular	
  products	
  from	
  pyrolysis.	
  	
  
o ECH	
   of	
   F3	
   fraction:	
   	
   Currently,	
   the	
   ECH	
   of	
   the	
   F3	
   fraction	
   did	
   not	
   provide	
   an	
  
interpretable	
   outcome	
   because	
   the	
   lignin	
   fraction	
   likely	
   polymerized	
   during	
   ECH.	
  
Exploration	
   of	
   different	
   electrolytes	
   and	
   electrocatalytic	
   conditions	
   might	
  
depolymerize	
  the	
  EAP	
  lignin	
  into	
  components	
  than	
  can	
  be	
  further	
  reduced	
  by	
  ECH.	
  	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

81	
  
	
  

	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
REFERENCES	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  
	
  

82	
  
	
  

	
  
REFERENCES	
  	
  
	
  
1.	
  

Galbe,	
  M.;	
  Zacchi,	
  G.,	
  Pretreatment	
  of	
  Lignocellulosic	
  Materials	
  for	
  Efficient	
  
Bioethanol	
  Production.	
  In	
  Biofuels,	
  Olsson,	
  L.,	
  Ed.	
  Springer	
  Berlin	
  Heidelberg:	
  2007;	
  
Vol.	
  108,	
  pp	
  41-­‐65.	
  

2.	
  

Yat,	
  S.	
  C.;	
  Berger,	
  A.;	
  Shonnard,	
  D.	
  R.,	
  Kinetic	
  characterization	
  for	
  dilute	
  sulfuric	
  acid	
  
hydrolysis	
  of	
  timber	
  varieties	
  and	
  switchgrass.	
  Bioresource	
  Technology	
  2008,	
  99	
  (9),	
  
3855-­‐3863.	
  

3.	
  

Sun,	
  Y.;	
  Cheng,	
  J.,	
  Hydrolysis	
  of	
  lignocellulosic	
  materials	
  for	
  ethanol	
  production:	
  a	
  
review.	
  Bioresource	
  Technology	
  2002,	
  83	
  (1),	
  1-­‐11.	
  

4.	
  

Keshwani,	
  D.	
  R.;	
  Cheng,	
  J.	
  J.,	
  Switchgrass	
  for	
  bioethanol	
  and	
  other	
  value-­‐added	
  
applications:	
  A	
  review.	
  Bioresource	
  Technology	
  2009,	
  100	
  (4),	
  1515-­‐1523.	
  

5.	
  

Bals,	
  B.;	
  Rogers,	
  C.;	
  Jin,	
  M.;	
  Balan,	
  V.;	
  Dale,	
  B.,	
  Evaluation	
  of	
  ammonia	
  fibre	
  expansion	
  
(AFEX)	
  pretreatment	
  for	
  enzymatic	
  hydrolysis	
  of	
  switchgrass	
  harvested	
  in	
  different	
  
seasons	
  and	
  locations.	
  Biotechnology	
  for	
  Biofuels	
  C7	
  -­	
  1	
  2010,	
  3	
  (1),	
  1-­‐11.	
  

6.	
  

Dale,	
  B.;	
  Weaver,	
  J.;	
  Byers,	
  F.	
  M.,	
  Extrusion	
  processing	
  for	
  ammonia	
  fiber	
  explosion	
  
(AFEX).	
  Applied	
  Biochemistry	
  and	
  Biotechnology	
  1999,	
  77	
  (1-­‐3),	
  35-­‐45.	
  

7.	
  

Dale,	
  B.	
  E.,	
  Biobased	
  Industrial	
  Products:	
  Bioprocess	
  Engineering	
  When	
  Cost	
  Really	
  
Counts.	
  Biotechnology	
  Progress	
  1999,	
  15	
  (5),	
  775-­‐776.	
  

8.	
  

Moniruzzaman,	
  M.;	
  Dien,	
  B.;	
  Ferrer,	
  B.;	
  Hespell,	
  R.;	
  Dale,	
  B.;	
  Ingram,	
  L.;	
  Bothast,	
  R.,	
  
Ethanol	
  production	
  from	
  AFEX	
  pretreated	
  corn	
  fiber	
  by	
  recombinant	
  bacteria.	
  
Biotechnology	
  Letters	
  1996,	
  18	
  (8),	
  985-­‐990.	
  

9.	
  

Yang,	
  H.;	
  Yan,	
  R.;	
  Chen,	
  H.;	
  Lee,	
  D.	
  H.;	
  Zheng,	
  C.,	
  Characteristics	
  of	
  hemicellulose,	
  
cellulose	
  and	
  lignin	
  pyrolysis.	
  Fuel	
  2007,	
  86	
  (12-­‐13),	
  1781-­‐1788.	
  

10.	
  

Lu,	
  Q.;	
  Li,	
  W.-­‐Z.;	
  Zhu,	
  X.-­‐F.,	
  Overview	
  of	
  fuel	
  properties	
  of	
  biomass	
  fast	
  pyrolysis	
  oils.	
  
Energy	
  Conversion	
  and	
  Management	
  2009,	
  50	
  (5),	
  1376-­‐1383.	
  

11.	
  

Bu,	
  Q.;	
  Lei,	
  H.;	
  Zacher,	
  A.	
  H.;	
  Wang,	
  L.;	
  Ren,	
  S.;	
  Liang,	
  J.;	
  Wei,	
  Y.;	
  Liu,	
  Y.;	
  Tang,	
  J.;	
  Zhang,	
  
Q.;	
  Ruan,	
  R.,	
  A	
  review	
  of	
  catalytic	
  hydrodeoxygenation	
  of	
  lignin-­‐derived	
  phenols	
  
from	
  biomass	
  pyrolysis.	
  Bioresource	
  Technology	
  2012,	
  124	
  (0),	
  470-­‐477.	
  

12.	
  

da	
  Costa	
  Sousa,	
  L.	
  Extractive	
  ammonia	
  (EA):	
  A	
  novel	
  ammonia-­‐based	
  pretreatment	
  
technology	
  for	
  lignocellulosic	
  biomass.	
  3615300,	
  Michigan	
  State	
  University,	
  Ann	
  
Arbor,	
  2014.	
  

83	
  
	
  

	
  
13.	
  

Li,	
  Z.;	
  Garedew,	
  M.;	
  Lam,	
  C.	
  H.;	
  Jackson,	
  J.	
  E.;	
  Miller,	
  D.	
  J.;	
  Saffron,	
  C.	
  M.,	
  Mild	
  
electrocatalytic	
  hydrogenation	
  and	
  hydrodeoxygenation	
  of	
  bio-­‐oil	
  derived	
  phenolic	
  
compounds	
  using	
  ruthenium	
  supported	
  on	
  activated	
  carbon	
  cloth.	
  Green	
  Chemistry	
  
2012,	
  14	
  (9),	
  2540-­‐2549.	
  

14.	
  

Zhang,	
  L.;	
  Xu,	
  C.;	
  Champagne,	
  P.,	
  Overview	
  of	
  recent	
  advances	
  in	
  thermo-­‐chemical	
  
conversion	
  of	
  biomass.	
  Energy	
  Conversion	
  and	
  Management	
  2010,	
  51	
  (5),	
  969-­‐982.	
  

15.	
  

Czernik,	
  S.;	
  Bridgwater,	
  A.	
  V.,	
  Overview	
  of	
  Applications	
  of	
  Biomass	
  Fast	
  Pyrolysis	
  Oil.	
  
Energy	
  &	
  Fuels	
  2004,	
  18	
  (2),	
  590-­‐598.	
  

16.	
  

Oasmaa,	
  A.;	
  Czernik,	
  S.,	
  Fuel	
  Oil	
  Quality	
  of	
  Biomass	
  Pyrolysis	
  OilsState	
  of	
  the	
  Art	
  for	
  
the	
  End	
  Users.	
  Energy	
  &	
  Fuels	
  1999,	
  13	
  (4),	
  914-­‐921.	
  

17.	
  

Kim,	
  T.-­‐S.;	
  Kim,	
  J.-­‐Y.;	
  Kim,	
  K.-­‐H.;	
  Lee,	
  S.;	
  Choi,	
  D.;	
  Choi,	
  I.-­‐G.;	
  Choi,	
  J.	
  W.,	
  The	
  effect	
  of	
  
storage	
  duration	
  on	
  bio-­‐oil	
  properties.	
  Journal	
  of	
  Analytical	
  and	
  Applied	
  Pyrolysis	
  
2012,	
  95,	
  118-­‐125.	
  

18.	
  

Gani,	
  A.;	
  Naruse,	
  I.,	
  Effect	
  of	
  cellulose	
  and	
  lignin	
  content	
  on	
  pyrolysis	
  and	
  
combustion	
  characteristics	
  for	
  several	
  types	
  of	
  biomass.	
  Renewable	
  Energy	
  2007,	
  32	
  
(4),	
  649-­‐661.	
  

19.	
  

Yang,	
  H.;	
  Yan,	
  R.;	
  Chen,	
  H.;	
  Zheng,	
  C.;	
  Lee,	
  D.	
  H.;	
  Liang,	
  D.	
  T.,	
  In-­‐Depth	
  Investigation	
  of	
  
Biomass	
  Pyrolysis	
  Based	
  on	
  Three	
  Major	
  Components:  	
  Hemicellulose,	
  Cellulose	
  and	
  
Lignin.	
  Energy	
  &	
  Fuels	
  2005,	
  20	
  (1),	
  388-­‐393.	
  

20.	
  

Nowakowski,	
  D.	
  J.;	
  Bridgwater,	
  A.	
  V.;	
  Elliott,	
  D.	
  C.;	
  Meier,	
  D.;	
  de	
  Wild,	
  P.,	
  Lignin	
  fast	
  
pyrolysis:	
  Results	
  from	
  an	
  international	
  collaboration.	
  Journal	
  of	
  Analytical	
  and	
  
Applied	
  Pyrolysis	
  2010,	
  88	
  (1),	
  53-­‐72.	
  

21.	
  

Patwardhan,	
  P.	
  R.;	
  Brown,	
  R.	
  C.;	
  Shanks,	
  B.	
  H.,	
  Understanding	
  the	
  Fast	
  Pyrolysis	
  of	
  
Lignin.	
  Chemsuschem	
  2011,	
  4	
  (11),	
  1629-­‐1636.	
  

22.	
  

Lei,	
  H.;	
  Ren,	
  S.;	
  Julson,	
  J.,	
  The	
  Effects	
  of	
  Reaction	
  Temperature	
  and	
  Time	
  and	
  Particle	
  
Size	
  of	
  Corn	
  Stover	
  on	
  Microwave	
  Pyrolysis.	
  Energy	
  &	
  Fuels	
  2009,	
  23	
  (6),	
  3254-­‐
3261.	
  

	
  
	
  

84	
  
	
  

	
  
Chapter	
  4	
  : Conclusions	
  and	
  Future	
  Work	
  	
  
Conclusions	
  	
  
Two	
   extracted	
   ammonia	
   process	
   (EAP)	
   lignin	
   fractions	
   (F1	
   and	
   F3)	
   were	
  
characterized	
  to	
  assess	
  the	
  potential	
  of	
  these	
  fractions	
  to	
  serve	
  as	
  pyrolysis	
  feed	
  material.	
  
Elemental	
   analysis	
   indicated	
   that	
   the	
   F3	
   fraction	
   had	
   lower	
   oxygen	
   and	
   higher	
   carbon	
  
contents	
   than	
   the	
   F1	
   fraction,	
   making	
   F3	
   a	
   more	
   desirable	
   feed	
   material	
   for	
   liquid	
   fuel	
  
production	
   via	
   fast	
   pyrolysis.	
   Thermogravimetric	
   analysis	
   	
   (TGA)	
   of	
   this	
   F3	
   fraction	
  
indicated	
  a	
  major	
  thermal	
  event	
  around	
  354	
  °C	
  with	
  the	
  DTG	
  profile	
  extending	
  over	
  a	
  large	
  
range	
  of	
  temperatures	
  as	
  is	
  typical	
  for	
  the	
  thermal	
  degradation	
  of	
  lignin	
  rich	
  feed.	
  Pyrolysis	
  
GC/MS	
   analysis	
   indicated	
   the	
   formation	
   of	
   phenolic	
   monomers	
   typical	
   of	
   lignin	
   derived	
  
compounds	
   in	
   bio-­‐oil.	
   ECH	
   of	
   the	
   F3	
   fraction	
   was	
   performed	
   under	
   basic	
   conditions	
   to	
  
assess	
  the	
  potential	
  of	
  ECH	
  for	
  lignin	
  depolymerization.	
  In	
  this	
  case	
  the	
  polymerization	
  of	
  
the	
  lignin	
  might	
  have	
  occurred	
  so	
  further	
  studies	
  need	
  to	
  be	
  conducted	
  to	
  explore	
  various	
  
conditions	
  that	
  might	
  support	
  the	
  depolymerization	
  of	
  this	
  fraction	
  instead	
  of	
  polymerizing	
  
it.	
  	
  
Studies	
   on	
   2-­‐methoxyphenol,	
   3-­‐methoxyphenol	
   and	
   4-­‐methoxyphenol	
   were	
  
performed	
  to	
  study	
  the	
  effect	
  of	
  different	
  positions	
  of	
  the	
  methoxy	
  group	
  on	
  the	
  aromatic	
  
ring.	
   Results	
   indicated	
   no	
   major	
   effect	
   of	
   the	
   position	
   of	
   the	
   groups.	
   Cyclohexanol	
   and	
  
methoxycyclohexanol	
   were	
   observed	
   as	
   products	
   for	
   all	
   cases	
   with	
   almost	
   equal	
  
selectivities.	
  Highest	
  conversion	
  was	
  observed	
  for	
  2-­‐methoxypehnol.	
  	
  Current	
  efficiency	
  for	
  
all	
   cases	
   was	
   modest	
   with	
   2-­‐methoxyphenol	
   showing	
   a	
   slightly	
   better	
   value	
   of	
   20%.	
   In	
  
studying	
   the	
   lignin	
   dimer	
   4-­‐phenoxyphenol,	
   conversion	
   of	
   the	
   substrate	
   to	
   phenol	
   and	
  
cyclohexanol	
  was	
  observed	
  confirming	
  the	
  ability	
  of	
  the	
  Ru/ACC	
  to	
  cleave	
  4-­‐O-­‐5	
  linkages.	
  
85	
  
	
  

	
  
ECH	
   was	
   performed	
   using	
   different	
   electrolytes,	
   substrate	
   concentrations	
   and	
   current	
  
densities	
  to	
  study	
  the	
  effect	
  of	
  these	
  conditions	
  on	
  product	
  yield,	
  selectivity,	
  conversion	
  and	
  
current	
   efficiency.	
   Lower	
   current	
   density	
   strongly	
   favored	
   phenol	
   selectivity	
   while	
   high	
  
current	
  density	
  favored	
  cyclohexanol	
  selectivity.	
  1	
  M	
  NaOH	
  gave	
  the	
  highest	
  product	
  yield.	
  	
  
A	
  β-­‐O-­‐4	
  linked	
  dimer	
  was	
  also	
  subjected	
  to	
  ECH	
  resulting	
  in	
  the	
  production	
  of	
  guaiacol	
  and	
  
vanillin.	
  Further	
  studies	
  need	
  to	
  be	
  conducted	
  to	
  probe	
  the	
  mechanism	
  of	
  the	
  cleavage	
  of	
  
this	
  linkage	
  type.	
  	
  
Reusing	
  the	
  catalyst	
  five	
  times	
  for	
  the	
  ECH	
  of	
  4-­‐phenoxyphenol	
  was	
  performed	
  for	
  
catalyst	
  deactivation	
  studies.	
  The	
  results	
  indicated	
  the	
  gradual	
  deactivation	
  of	
  the	
  catalyst	
  
after	
  each	
  experiment.	
  Due	
  to	
  residual	
  cyclohexanol	
  adsorbed	
  to	
  the	
  catalyst,	
  cyclohexanol	
  
yield	
  for	
  the	
  second	
  experiment	
  was	
  higher	
  than	
  that	
  of	
  the	
  other	
  experiment	
  also	
  resulting	
  
in	
   higher	
   apparent	
   current	
   efficiency	
   for	
   that	
   run.	
   	
   Efforts	
   should	
   be	
   made	
   to	
   wash	
   the	
  
catalyst	
   effectively	
   to	
   extract	
   cyclohexanol	
   before	
   reusing	
   it.	
   The	
   effects	
   of	
   different	
  
solvents	
  should	
  be	
  studied	
  to	
  achieve	
  this	
  goal.	
  	
  
Future	
  Work	
  
	
  

As	
  a	
  way	
  of	
  exploring	
  the	
  potential	
  of	
  this	
  pyrolysis/electrocatalysis	
  system	
  for	
  the	
  

depolymerization	
  and	
  valorization	
  of	
  extractive	
  lignin,	
  here	
  are	
  a	
  few	
  future	
  plans:	
  
1. Further	
   characterization	
   of	
   the	
   EAP	
   lignin	
   should	
   be	
   performed	
   to	
   define	
   the	
  
detailed	
  structure	
  of	
  the	
  lignin.	
  	
  
2. Overall	
  yield	
  determination	
  of	
  lignin	
  pyrolysis	
  using	
  py-­‐GC/MS.	
  
3. Small-­‐scale	
   pyrolysis	
   of	
   the	
   EAP	
   lignin	
   should	
   be	
   performed	
   to	
   produce	
   usable	
  
quantities	
  of	
  bio-­‐oil	
  for	
  ECH	
  studies.	
  	
  

86	
  
	
  

	
  
4. Different	
   conditions	
   should	
   be	
   explored	
   for	
   the	
   direct	
   ECH	
   of	
   EAP	
   lignin	
   to	
  
determine	
   whether	
   ECH	
   may	
   function	
   independently	
   as	
   a	
   viable	
   depolymerization	
  
scheme.	
  	
  
5. ECH	
   of	
   a	
   number	
   of	
   lignin-­‐derived	
   bio-­‐oil	
   monomers	
   and	
   mixtures	
   of	
   monomers	
  
should	
   be	
   performed	
   to	
   determine	
   the	
   effectiveness	
   of	
   this	
   process	
   for	
   lignin	
  
derived	
  bio-­‐oil	
  upgrading.	
  	
  
6. ECH	
  of	
  other	
  types	
  of	
  lignin	
  linkages	
  should	
  be	
  explored	
  to	
  build	
  upon	
  the	
  existing	
  
work.	
  	
  
7. Efforts	
  should	
  be	
  made	
  to	
  improve	
  the	
  modest	
  current	
  efficiency	
  of	
  the	
  system.	
  
8. Studies	
   should	
   be	
   done	
   to	
   determine	
   the	
   exact	
   cause	
   of	
   catalyst	
   deactivation	
   and	
  
how	
  the	
  catalyst	
  can	
  be	
  reactivated.	
  	
  
9. Explore	
  other	
  less	
  expensive	
  metals	
  as	
  catalysts.	
  	
  

87