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Production of Soluble and Hydrolyzable Carbohydrates from Biomass Using THF/Water Co-solvent in the Presence of Acid Catalyst Arpa Ghosh and Robert C. Brown Bioeconomy Institute, Iowa State University Symposium on Thermal and Catalytic Sciences for Biofuels and Biobased Products, Nov 3rd 2016
2 1Miretal.,2014
Enzymatic Hydrolysis is the Conventional Pathway for Production of Cellulosic Sugar1
Challenges in Producing Cellulosic Sugars via Enzymatic Hydrolysis • Cost of enzyme production2, 3
- Covers 20% of total production cost of fermentable carbohydrates
- Estimated cost up to $1.47 per gallon of ethanol
• Slow rates of bioconversion4
- It takes days or even weeks to reach glucose yields >70%
• Achieving high concentration of sugar
products5 - Sugar required for fermentation is ~120 g/L
• Substrate specific enzyme production could be uneconomical
3
2Lyndetal.,20083Klein-Marcuschameretal.,20124Nguyenetal.,20155Gaoetal.,2014
Cellulosic Fermentation Substrates via Thermochemical Routes
• Gasification with syngas fermentation
• Fast pyrolysis and hydrolysis
• Concentrated acid hydrolysis
• Solvent liquefaction and fermentation of soluble carbohydrates
4
Ø Mildtemperature(150-400oC)Ø DiluEonpreventssecondaryreacEonsØ EasyrecoveryassolubilizedcarbohydratesØ Minimalaciduse
✔
PolarSolvents
AproEcsolventProEcsolvent
SolventcanparEcipateinreacEonbyaH-bondingor
proton(H+)donaEon
5
SolventdoesnotjointhereacEonbyH-bondingorproton(H+)donaEon
SecondaryreacEonssuppressed
SlowerrateofbiomassdecomposiEon
ProducEonofhumicspecies
AcceleratedrateofdecomposiEon
Liquefaction Using Hot, Pressurized Solvent
(Water,methanol,ethanol)(1,4-dioxane,THF,acetone,GVL)
Solubilized Carbohydrates Production Using Polar Aprotic Solvents
• Production of 68% soluble carbohydrates (65% C6 and 73% C5 sugars) from woody biomass at 157-217oC in 2 h using GVL and water with acid catalyst6
• Rapid deconstruction of cellulose into >60% solubilized carbohydrates in a wide range of polar aprotic at high temperature and pressure7
• Enhanced digestibility of cellulose by enzymes with THF-water co-solvent pretreatment4
6 6Luterbacheretal.,2014 7Ghoshetal.,2016 4Nguyenetal.,2015
Practical Challenges in Using Polar Aprotic Solvents High polarity solvents • High cost of these solvents demands quantitative recovery
• Recovery of solvent is often complex such as the use of liquid CO2 extraction for GVL recovery
Low polarity solvents • High temperature and high pressure processing
associated with these solvents increases capital and operating costs
7
Addition of Acid Catalyst Makes Low-polarity Solvents as Effective as High-polarity Solvents
8
• Levoglucosanyieldincreaseswithpolarityofsolventinabsenceofacid7
• Theeffectofpolarityisadjusted
byaddingverydiluteacidtothesolvents
7Ghoshetal.,2016
1,4-dioxane
THF Acetone
GVLAcetonitrile
05101520253035404550
0 10 20 30
Levoglucosan
yield(%
)
Polarsolubilityparameter,MPa1/2
AtTset350oC
Withoutacid With0.5mMacid
(Meanyieldsfromatleastduplicateexperimentsreportedwithstandarderror<10%ofmean)
PolaraproEcsolvent
H+Cellulose
Levoglucosan(primarycarbohydrateproduct)
Goals and Hypothesis THF-water with dilute acid catalyst
• Solubilize lignin and partially decompose hemicellulose in a mild pretreatment step with cellulose remaining intact
• Rapidly decompose the resulting cellulose-rich fraction into soluble carbohydrates at hot, pressurized condition in solvent liquefaction
9
Develop solvent liquefaction (SL) process to replace enzymatic hydrolysis to produce cellulosic sugars • Significant increase of sugar
production rates with respect enzymatic hydrolysis
• Competitive soluble carbohydrates yields with current SL methods
• Using biomass-sourced, relatively low-cost solvent with easy recovery process
Tetrahydrofuran(THF)b.p.66oC
Biomass Multistep Solvent Liquefaction Using THF/water with Sulfuric Acid Catalyst
10
FluidizedHeaEngBed
Solubilizedproduct
Solidresidue
Carbohydratemonomers64%ofGlucose35%ofXylose
Solubilizedlignin&
hemicellulose
Cellulose-richpulp
RecyclableTHF
SolventLiquefacEon2min220oC
THFrecovery&sealing FiltraEon
Hydrolysis135oC44min25mMH2SO4
Watersolubles&precipitated
lignin
53%ofXylose3%ofC6sugar
45%oflignin
Redoak300-710μm
Pretreatment30-60min120oC
Water
80/20vol%THF/Waterwith1wt%H2SO4
80/20vol%THF/Water
Reactor
0.5-2wt%H2SO4
3wt%
5wt%
Definitions: Carbohydrate Monomer Yield and Delignification
11
IniEalC5and/orC6polysaccharidesinbiomass
Carbohydratemonomer
yield(wt%)
= X100%MassofhydrolyzedC5and/orC6monomerproduct
IniEallignininbiomassDelignificaEon
(%)= X100%
Massofligninobtainedasby-productfrompretreatment
2.1% 1.7%
19.1%
0.9%40.7%
Redoakpolysaccharides8,9
Mannan(wt%)
Galactan(wt%)
Xylan(wt%)
Araban(wt%) 8Conner,1984 9Choietal.,2014
IniEalmassofbiomasspriortopretreatment
Productyield(wt%) = X100%
Massofproductfromtheprocess
Longer Pretreatment Times and Higher Acid Loadings Produce Desired Pulp Yields
12
PretreatmentEmedoesnotincludeheat-upEme
83%73%
61%
81%
69%56%
0%
20%
40%
60%
80%
100%
0.5 1 2
PulpYield(w
t%)
Acidloading(wt%ofredoak)
30min 60min
40.7%
22.8%
33.3%
0.4%
RedoakcomposiOon(wt%)9
Cellulose
Hemicellulose
Lignin
Ash
9Choietal.,2014
Longer Pretreatment Times and Higher Acid Loadings in Delignifing Biomass and Solubilizing Polysaccharide
0%
10%
20%
30%
40%
50%
0.5 1 2
DelignificaO
on
Acidloading(wt%ofredoak)
EffectofpretreatmentcondiOonsondelignificaOonofbiomass
30minpretreatment
60minpretreatment
13
0
10
20
30
40
50
60
0 1 2
Yield(w
t%)
Acidloading(wt%ofredoak)
EffectofpretreatmentcondiOonsonpolysaccharidesolubilizaOon
C6sugarsat30minC5sugarat30minC6sugarsat60minC5sugarat60min
PretreatmentEmedoesnotincludeheat-upEme
Cellulosealmostintact
Xylose53%
Pretreatment Enhances Soluble and Hydrolyzable Sugar Yields from Red Oak
14
73%
44%
0%
20%
40%
60%
80%
100%
Pretreatedredoak
Redoak
Yield(w
t%)
Totalsolubleandhydrolyzablecarbohydrates
(YieldsfromcombinedpretreatmentandsolventliquefacEonsteps)
67%
30%
88%
73%
0%
20%
40%
60%
80%
100%
Pretreatedredoak
Redoak
Yield(w
t%)
HydrolyzedC5andC6carbohydratemonomers
GlucoseasC6monomer XyloseasC5monomer
Overall Mass and Polysaccharides Balance in Multi-step Biomass Solvent Liquefaction
15
32.2%
5.1%
16.8%
4.3%
15.0%
14.3%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Prod
ucty
ield(w
t%)
BasedoniniOalbiomass
Solidresidue
Ligninextracted
Furfural
Xylose
5-HMF
Glucose
Processstep Yield(wt%) Pretreatment C6sugars 1.5% Xylose 10.2% SolventliquefacOonGlucose 30.7% 5-HMF 5.1% Xylose 6.6% Furfural 4.3% TotalGlucanproducts 37.3% TotalXylanproducts 21.1% IniEalGlucan 40.7% IniEalXylan 19.1% Glucanbalance 91.6% Xylanbalance 110.0%
Delignification Correlates to Solubilization of Polysaccharides
16
0%
20%
40%
60%
80%
0 20 40 60
Glucoseyield(w
t%)
DelignificaOon(%)
RelaOonshipofglucoseyieldswithdelignificaOon
0%
20%
40%
60%
80%
0 20 40 60
Xyloseyield(w
t%)
DelignificaOon(%)
RelaOonshipofxyloseyieldswithdelignificaOon
PretreatmenthemicellulosesolubilizaOon
SolventliquefacOoncellulosesolubilizaOon
(GlucoseandXyloseashydrolyzedproductsateachprocessstep)
Conclusions and Future Direction Significant augmentation of cellulosic sugar production technology with promise to replace enzymatic hydrolysis
ü Used biomass-sourced, easy-to-recover, low-cost solvent THF with qualities of rapidly deconstructing polysaccharides and delignifying biomass at relatively low temperatures
ü Dramatically increased sugar production rates compared to enzymatic hydrolysis ü Produced competitive total soluble carbohydrates yields (73%) with current
solvent liquefaction methods (68% in GVL-process)
Techno-economic analysis of THF-water solvent liquefaction process is necessary to evaluate its potential for cellulosic ethanol production
17
Acknowledgement
18
MajorProfessor:Prof.RobertC.BrownBioeconomyInsOtuteStaffandGraduatestudentsUndergraduateAssistants
Supplementary Slides
19
Temperature regime for maximizing soluble carbohydrates yields
0
50
100
150
200
250
300
0 2 4 6 8 10 12 14 16
Temp(oC)
Time(min)
3/8inchmini-reactor:THF/Water-acidmixtureHeat-up ReacEon Quench
Idealforsugar
producEon
20
Tset
Effect of Reaction Parameters on Soluble and Hydrolyzable Carbohydrate Yields
At1.25mMH2SO410vol%watercontent
At250oC 10vol%watercontent
21
At250oC 1.25mMH2SO4
Meanofduplicatesreportedwitherror<10%.YieldswereopEmizedwithrespecttoreacEonEme.
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
0 10 20 30Water%(vol%)
Effectofwatercontent
C6sugars
C5sugars
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
0 1 2 3AcidconcentraOon(mM)
EffectofacidconcentraOon
0.0%
20.0%
40.0%
60.0%
80.0%
100.0%
200 220 240 260 280
Yield(w
t%)
ReacOonTemperature(C)
Effectoftemperature
Effect of Water Content on Solid Yield and Carbohydrates Yields
22
0.0%10.0%20.0%30.0%40.0%50.0%60.0%70.0%80.0%90.0%
0%water
10%water
20%water
Yield(w
t%)
Watercontentinsolventmixture
Solids
Solubilizedproducts
Gas
0.0%10.0%20.0%30.0%40.0%50.0%60.0%70.0%80.0%90.0%
0%water
10%water
20%water
Yield(w
t%)
Watercontentinsolventmixture
C6sugars
C5sugars
SLcondiEon:220oCand2minat2.5mMH2SO4