Dr. Mark Crocker Associate Director, Center for Applied Energy Research University of Kentucky.
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Transcript of Dr. Mark Crocker Associate Director, Center for Applied Energy Research University of Kentucky.
Dr. Mark CrockerAssociate Director, Center for Applied Energy ResearchUniversity of Kentucky
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Mark Crocker Center for Applied Energy Research, University of Kentucky
2013 SEC Symposium
Lignin Deconstruction for the Production of Fuels and
Chemicals
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Overview
• Introduction & Background
• Our Approach• In planta modification to modify lignin fraction• Lignin dissolution in ionic liquids• Oxidative cleavage of lignin and lignin model compounds
• Summary & Conclusions
4
Introduction: Lignocellulosic biomass
- Plants made of lignin, cellulose and hemicellulose
- Amount of each polymer differs depending on plant species, the part of the plant, age and
environmental factors
- Structure of lignin polymer also varies
Sinapyl alcohol (S)
Coumaryl alcohol (H)
Coniferyl alcohol (G)
J. Zakzeski, P.C.A. Bruijnincx, A.L. Jongerius, B.M. Weckhuysen, Chem. Rev. 2010, 110, 3552
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Background: Why Lignin?
J. Zakzeski et al., Chem. Rev. 2010, 110, 3552
O
O
O
OH
OCH3
O
OCH3
O
O
OH
HO
CH3O
O
CHO
HO
O
O
OCH3
OH
OHO
CH3O
O
HO
CH3O
O
OCH3
O
OH
O
OCH3O
OCH3
O
O
HO
OCH3
HO
OH
OCH3
O
OH
OCH3OH
O
HO
O
OH
O
Y.H.P. Zhang, J. Ind. Microbiol. Biotechnol. 2008, 35, 367
Polymers, resins, dyes,pharmaceuticals
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Our ApproachDevelop new processes for the direct conversion of lignin to
liquid fuels and chemicals:
In planta modification thereby accentuating lignin
fraction and facilitating downstream processing.
S. DeBolt
Catalytic oxidative cleavage of the lignin at benzylic position
M. Meier, M. Crocker
Dissolution and controlled thermolysis in ionic liquids
S. Morton
Catalytic upgrading of lignin derived oxygenates
M. CrockerLignin Product Stream
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In planta Modification to Increase Lignin Content and Facilitate Downstream
Processing
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Chemical secretions from endophytic microbes elicit ectopic lignificationin model plant arabidopsis:
• Isolated fungal and bacterial endophytes from switchgrass: 1080 identified and categorized into their taxonomic diversity
• Grow cells, spin and separate media from cells - extract DNA from cells and sequence identify by rDNA
• Freeze dry and extract secretion as bulk
• Add to sterile plant growth media
• Test for ectopic lignin (via a dye reaction)
Application of Endophyte Secretions to Bioenergy Grasses
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The red giant was selected from a mutagenized population of Sorghum plants (2 year project in selection alone)
• Aim: sugars contained in stem can be converted to ethanol/ butanol and leaves can be converted to phenolics-based fuel
• Selected based on high phenolics in leaves• Little phenotype (loss of growth) relative to wild type plant• Grown over several generations (1 acre grown this year)
Application of Forward Genetics to Bioenergy Crops
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Py-GC/MS Analysis of Mutant SorghumIn
ten
sit
y (
a.u
.)
Wild Sorghum Leaf
1.6 4.6 7.5 10.513.416.419.322.325.228.231.134.137.040.042.945.948.851.7
Retention Time (min)
Inte
nsit
y (
a.u
.)
Mutant Sorghum Leaf
Total lignin (area %)
S:G (area %)
Wild type leaf
36.2 (+/- 2.8) 0.37 (+/- 0.01)
Mutant leaf
41.5 (+/- 1.3) 0.51 (+/- 0.03)
Mostly holocellulose pyrolysates
Mostly lignin pyrolysates
- Pyrolysis-GC/MS: analytical scale thermal decomposition directly coupled to GC/MS- Efficient method for analysis of polymers
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Lignin Dissolution in Ionic Liquids
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Ionic Liquids for Lignin Dissolution and ManipulationSynthetic Routes Toward Dialkyl Imidazolium Halides
+ R-X + R’-XX
X
• 1-alkyl imidazoles with alkyl groups larger than butyl are not commercially available
• Properties of long chain di-alkyl imidazolium halides are not well understood
1-Hexyl-3-Dodecyl Imidazolium Halide
Imidazole 1-Alkyl Imidazole 1-Alkyl-3-Alkyl’ Imidazolium Halide
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Butyl
Hexyl
Octyl
Decyl
Dodecyl
Lignin Dissolution in Alkyl-methyl Imidazolium Chlorides at 100 °C
0 min 30 min 60 min
• Lignin solubility decreases as alkyl chain length increases
• Butyl and hexyl show complete dissolution before 30 minutes
• Octyl and decyl show complete dissolution before 60 minutes
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Butyl
Hexyl
Octyl
Decyl
Dodecyl
Cellulose Dissolution in Alkyl-methyl Imidazolium Chlorides at 100 °C
0 min 30 min 60 min
• Cellulose solubility is much lower, but still decreases as alkyl chain length increases
• All failed to dissolve cellulose before 60 minutes
• Decyl and dodecyl demonstrated no impact on cellulose
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Dissolution of Biomass Constituents After 3 h at 100 °C
Cellulose Hemicellulose Lignin
Butyl
Hexyl
Octyl
Decyl
Dodecyl
0%
<50%
>50%
100%
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Oxidative Cleavage of Lignin and Lignin Model Compounds
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Linkage B-O-4 B-5 5-5
Structure
Abundance in Hardwood 60% 6% 9%
Linkage 4-O-5 B-B B-1
Structure
Abundance in Hardwood
6.5% 3% 7%
O
OH
R
OO
O
R
1
23
4
O
54
HO
OR
O
R
O
R
O
R
O
R
O
R
5
5
1
2
34
43
2
1
O
4
5
O OH
O
R
1
2
3
4
R 12
3
OO
O
R
O
O
R
O
OH
OH
1
O
R
O
O
O
R
J. Zakzeski et al., Chem. Rev. 2010, 110(6), 3552
Common Linkages Present in Hardwood Lignin (Spruce)
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Our Approach for Lignin Deconstruction
Oxidation Sequence for Simple Model Compounds
LDH, O2 (1 atm)
Diphenyl ether90oC, 24 h
1.3 eq. m-CPBA1,2-dichloroethane
70oC, 24 h
LDH = Ni/Al layered double hydroxide,B.M. Choudary et al., Angew. Chem. 2001, 113, 785.
58% yield
85% yield
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Compounds Modeling the β-O-4 Linkage in Lignin
Cmp Substituent
1 R1, R2, R3, R4, R5, R6 = H
2 R1, R2, R4, R6 = H, R3 = OH, R5 = n-Pr
3 R1, R2, R6 = CH3O, R3 = OH, R4 = CH3, R5 = n-Pr
4 R1, R6, = CH3O, R2, R3 = OH, R4 = CH3, R5 = n-Pr
5 R1, R2, R6 = CH3O, R3 = OH, R4 = CH2OH, R5 = n-Pr
6 R1, R6, = CH3O, R2, R3 = OH, R4 = CH2OH, R5 = n-Pr
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Selective Aerobic Oxidation of Benzylic Alcohol Groups Using TEMPO, NaNO2
Cmpd Conv (%) A (% yield)
1 0 -
2 100 100
3 100 81
4 polymer -
5 100 80
6 polymer -
A
TEMPO, NaNO2,
HCl, NaCl, CH2Cl2,
O2 balloon, 25°C
Wang, L.; Li, J.; Yang, H.; Lv, Y.; Gao, S. J. Org. Chem. 2012, 77, 790
Excellent conversion and selectivity!
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Cα-Cβ Bond Cleavage via Baeyer-Villiger Oxidation and Hydrolysis
Cmpd Conv (%) C (% yield) D (% yield)
2’ 90 10 -
3’ 100 - 81
C D
Liou, L., Huang, C.; Int. J. Appl. Sci. Eng. 2006, 4, 3
Note – Compounds 2’ and 3’ are benzylic alcohol group oxidation products of 2 and 3
30% H2O2
HCOOH, 1,2-DCE
Most of the oxidized material hydrolyzes in the reaction mixture Clearly, the ketones undergo B-V oxidation as expected
7 9 11 13 15 17 19 21
Retention Time (Minutes)
Rela
tive
Abso
rban
ce
MW 173: m-CPBA
OL + (i) benzylic oxidn.+ (ii) Baeyer-Villiger oxidn.+ (iii) transesterification
M.W. 256:
Organosolv lignin (OL)
OL + benzylic oxidation
O
OH
First Attempts at Lignin Deconstruction
Mobile phase: DMSO/THF; Column: PSS Suprema, Linear S Diode array detector (320 nm)
OCH3H3CO
OHOCH3
CHO
OHOCH3H3CO
CHO
OH
Retention time (min)
+ dimers
GPC analysis:
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Summary & Conclusions
• In planta approaches have been successfully applied to increase lignin/phenolic content in plants
• Mutations in sorghum result in changes in lignin structure and composition as seen by Py-GC/MS
• Ionic liquids have been developed which permit selective dissolution of lignin in biomass
• Oxidative cleavage of lignin β-O-4 model compounds has been demonstrated by a sequence of benzylic alcohol oxidation, Baeyer-Villiger oxidation and hydrolysis
• This methodology is being applied to lignin
• Efforts to manipulate the structure of lignin and to effect its deconstruction are still in their infancy
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Acknowledgements
• NSF – Dr. George Antos
• Dr. Rodney Andrews (PI), Dr. Seth DeBolt (co-I), Dr. Mark Meier (co-I), Dr. Samuel Morton (co-I)
• Students, postdocs and staff:
Anne Harman-Ware Nikhil PatilJustin Mobley Aman KaurRobby Pace Soledad YaoAndy Placido Dr. Venu MenduCharles Thacker Dr. Carloalberto PettiDr. James Hower Brian Williams
This work supported by a grant from the National Science FoundationNSF AWARD: EFRI-0937657
Dr. Mark CrockerAssociate Director, Center for Applied Energy ResearchUniversity of Kentucky