College of EngineeringCollege of Agriculture
Biochemical and Biomimetic Approaches to Saccharifying Biomass for Advanced BiofuelProduction
Center for direct
catalytic conversion
of biomass to biofuels
(C3Bio)
Nathan S. Mosier
Acknowledgements› Purdue University
– College of Agriculture
– College of Engineering
– C3Bio
– Energy Center
– Laboratory of Renewable Resources Engineering
› Funding Sources
– DOE-BES (C3Bio) DE-SC0000997
– NSF BES-9727096, IGERT-9987576
– Purdue Ag. Research Station
Value from Corn Lignocellulose
› Stover and Fiber
› Pathways to Value-added Products
– Biochemical
– Thermochemical
› Challenge is fractionation and conversion at low cost and high yield
CelluloseLignin
Hemicellulose
Simplified Impact of Pretreatment on Biomass
Mosier, N. et al. Bioresource Technology 96(6):673-686 (2005).
Pretreatment
555
Introduction Catalysts for Cellulosic Polysaccharide Hydrolysis
�H2SO4, HCl (mineral acids)
�H2O
O
H
H
�H2SO4, HCl (mineral acids)
�H2O
O
H
H
�H2SO4, HCl (mineral acids)
�H2O
O
H
H
�Cellulases�Cellulosomes
�Cellulases�Cellulosomes
Small molecular catalysts Protein catalysts
• Low selectivity;
• Low sugar yield;
• Fast reaction under severe
reaction condition (160-
250 °C, pH 0-2).
• High specificity & selectivity;
• Limited mass transfer (hindered
substrate access);
• Slow reaction under mild
condition (50 °C, pH 4.8).
Concept of a Biomimetic Catalyst
downsizing
MW 55kD
active site
Cellulolytic Enzyme
only active site
residue carboxylate
pair retained
downsizing
Thousands of Daltons
active site
Cellulolytic Enzyme Biomimetic Catalyst
only active site
residue carboxylate
pair retained
Hundreds of Daltons
Enhanced Activity - Control Catalyst Specificity- Higher Mass Transfer- Higher Temperatures
0
10
20
30
40
50
60
70
80
90
100
Corn Stover Switchgrass Poplar
% R
eco
ve
red
in
Aq
ue
ou
s P
ha
se
Xylose
Glucose
Maleic Acid: Selective Fractionation
50 mM
160 C
20 Min
Mosier, Purdue
Abu-Omar, Purdue
CONCLUSIONS
Maleic Acid Pretreatment
(170°C, 8min, 200 mM)
Sulfuric Acid Pretreatment
(179 °C, 6.2 min, 1.16%)
Xylose Yield ~95% ~68%
Furfural
Concentration~1.80 g/L ~8.00 g/L
• Fermentation of Resulting Xylose
– 87% of theoretical ethanol can be generated by Purdue-Ho yeast fermenting hydrolysate
– This yield is equivalent to pure xylose in YEP medium
ENZYME DIGESTABILITY OF PRETREATED CORN STOVER
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 12 24 36 48 60 72 84 96 108 120 132
GL
UC
OS
E Y
IEL
D
ENZYME HYDROLYSIS TIME, HOURS
MALEIC ACID PRETREATED
SULFURIC ACID PRETREATED
UNTREATED
Enzyme Hydrolysis of Three Types of Corn Stover in 120 Hours
(4% Solid-Loading for the Pretreatment)
Kinetics Analysis
Biomass
khydrolysis
khydrolysis is a function of H+
(independent of source)
pH Affects Dehydration of Xylose
Kinetics solely dependent on [H+],
indicating specific acid catalysis mechanism
y = -0.0075xR² = 0.9379
y = -0.0241xR² = 0.9863
y = -0.0468xR² = 0.9784
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0 5 10 15 20 25
ln (X
/X0)
Reaction time, minutes
10mM
50 mM
100 mM
y = 0.473xR² = 0.9896
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
0.05
0 0.05 0.1 0.15
kd
eg, m
in-1
[H+], mole
Organic/Weak Acids
Kinetics dependent on [Acetic acid] at constant pH,
indicating general acid catalysis mechanism
y = -0.0081xR² = 0.9634
y = -0.0111xR² = 0.9493
y = -0.0178xR² = 0.9944
-0.4
-0.4
-0.3
-0.3
-0.2
-0.2
-0.1
-0.1
0.0
0 5 10 15 20 25
ln (
X/X
0)
Reaction time, minutes
10mM
50 mM
100 mM
y = 0.1763xR² = 0.9628
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
0 0.05 0.1 0.15
kd
eg, m
in-1
[Acetic acid], mole
Unexpected Results
Kinetics inversely dependent on [Maleic acid] at constant pH,
Indicating inverse general acid catalysis mechanism
y = -0.007xR² = 0.9228
y = -0.003xR² = 0.7713
y = -0.0011xR² = 0.0211
-0.30
-0.25
-0.20
-0.15
-0.10
-0.05
0.00
0 10 20 30 40
ln (
X/X
0)
Reaction time, minutes
10mM
50 mM
100 mM
y = -0.0475x + 0.0062R² = 0.994
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0 0.05 0.1 0.15
kd
eg, m
in-1
[Maleic acid], mole
What the Kinetic Analysis Tells Us
� Maleic Acid Inhibitions Degradation of Xylose
� Inhibition of dehydration to furfural less than
degradation to humins
� Activation Energy of Dehydration Higher
� Activation Energy of Degradation to Humins
Lower
� Selectivity of Reactions of Xylose in
Presence of Maleic Acid Controlled by
Temperature
Thermochemical Route to Platform
Chemicals
15
18 MJ/kg
Xylose3H2O
24 MJ/kg
Furfural
100% C33% Higher Energy Density
Catalysis
Furans (precursor for levulinic acid, THF)
Bozell and Petersen, 2010
Selective hydrolysis and conversion: Tandem Catalysis
~170 °C, 10 min
+
Biomass Lignin & Cellulose Xylose≥ 80% yield
filter
~200 °C, 5-10 min
furfural≥ 60% yield
Maleic acid& 10 mol% ZnCl2
Maleic acid Pd/C
~ 10 min
Me-THF
H2
Pure sugar and biomass are NOT the same!
Sample Catalyst t/ min Xylose %
conversion
% Yield
furfural
Pure xylose
(10 g/L)
ZnCl2
0.25 M Maleic acid
0.25 M H2SO4
10
10
5
100
100
100
50
66
65
Corn Stover 0.25 Maleic acid
0.25 M H2SO4
10
5
100
100
69
55
Salts (especially halides) strongly affect
thermocatalytic processes
Conversion of Cellulose Difficult
– Not Just Recalcitrance
Nate Mosier
Mahdi Abu-Omar
Eurick Kim
Sugar kdeg
(*10-4s-1)
@ 180 C
Ea
(kJ/mol)
Glucose 1.0 120.0
Xylose 5.8 121.0
Fructose 123.0 18.1
Conversion of Cellulose Requires Paired Catalysis
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20
HMF %
Glu %
Fru %
LA %
180 C 2 phase solution
25mM AlCl3 H2O:MTHF
50mM Maleic Acid
AlCl3 Isomerizes Glucose to Fructose
Time, minutes
% in
itia
l C
Hydrolysis of Cellulose is Rate Limiting
0
10
20
30
40
50
60
70
% Y
ield
HMF
Ff
180 C, 60 minutes 2 phase solution
25mM AlCl3 H2O:MTHF
50mM Maleic Acid
Conclusions
• Mimetic approach attempts to achieve
catalytic selectivity similar to enzymes
• Maleic acid can fractionate biomass sugars at
high yields for biochemical and
thermocatalytic conversion
• Corn-derived sugars good feedstocks for
value-added chemicals and fuels