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