Formate-Assisted Pyrolysis of Biomass

TCS 2016

William J. DeSisto, M. Clayton Wheeler, Will Gramlich, Anushka Vithanage

University of Maine

Challenges in Biomass Pyrolysis

• Yield and energy losses during pyrolysis

– Poor H:C in biomass

– Recalcitrant fractions

• Oil quality

– Feedstock for upgrading

2

Challenges in Biomass Pyrolysis

• The oil quality in the first step impacts economics of the second step

biomass

and quality

bio-oil yield

pyrolysis

3

DeSisto and Wheeler, Biomass & Bioenergy (2016)

Motivation to Remove Oxygen During Pyrolysis

• Reduce operational costs for upgrading

• Produce a stable oil

• Produce an alternate oil composition

4

Some Examples

• Catalytic pyrolysis

• Catalytic hydropyrolysis

• Tail gas reactive pyrolysis

• Hydrothermal liquefaction

• Formate-assisted pyrolysis

• Addition of “active” hydrogen improves yields

5

Formic Acid from Biomass

• Formic acid has traditionally been used as a hydrogen donor in aqueous reactions

• Easily derived from biomass

• Formic acid cannot undergo ketonization, instead forms H2 and CO

+Δ

H+

2 + Ca(OH)2

-H2O

Δ H2 + CO + CaCO3

6

Ketonization with Formic Acid as Hydrogen Donor

+ + Ca(OH)2

-H2O

Δ

Formic/Levulinic Acid Ratio

% C

arb

on

Co

ntr

ibu

tio

n

Oil

Char

Carbonate

Aqueous + Gas

Case, et al., Green Chemistry (2012)

7

Co-Pyrolyze Biomass with FormateSalts

• Formate-Assisted Pyrolysis– Pine sawdust

– Wheat straw

– Lignin

– Tannins

– ~500 ºC

– Hot gas filtration

– atm-150 psi

8

Calcium Pretreatment• 0.43 g calcium/g pine loading

– CaSO4• Stable under heating

– Ca(COOH)2• Decomposes at ~450 °C to CaCO3 + CO + H2

– CaCO3• Stable under pyrolysis conditions

– Ca(OH)2• Decomposes to CaO + H2O at ~500 °C

– CaO• Reacts with CO2 to form CaCO3

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Increasing basicity

Case, et al. Bioresource Technology (2014)

Calcium Compounds Dramatically Lower Oxygen Content in Oil

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ESP Composition (wt %)

C H O O:C H:C

Pine feed 45.1 6.80 48.1 0.8 1.8

Pine pyrolysis oil 67.8 6.50 25.7 0.28 1.15

CaSO4 treated pyrolysis oil 65.7 6.33 27.9 0.32 1.16

Ca(COOH)2 treated pyrolysis oil 76.6 7.30 16.3 0.16 1.15

CaCO3 treated pyrolysis oil 78.7 6.99 14.3 0.14 1.07

Ca(OH)2 treated pyrolysis oil 81.6 7.26 11.1 0.10 1.07

CaO treated pyrolysis oil 82.9 7.16 9.94 0.09 1.03

Calcium formate pretreatment maintains high H:C ratio while a decreasing O:C ratio

Calcium Compounds Affect PyrolysisYields

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0

10

20

30

40

50

60

70

Water Organic product Char product Gas product

g p

rod

uct

/g b

iom

ass

fed

Pine CaSO4 Treated Pine

Ca(COOH)2 Treated Pine CaCO3 Treated Pine

Ca(OH)2 Treated Pine CaO Treated Pine

0

10

20

30

40

50

60

70

Pine CaSO4 Treated Pine

Ca(COOH)2 Treated Pine

CaCO3 Treated Pine

Ca(OH)2 Treated Pine

CaO Treated Pine

g/g

pin

eC2+ CH4 CO CO2

Yield improvement

Calcium Pretreatment Summary

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• All of the calcium compounds tested, except for CaSO4 had a dexoygenating effect during pyrolysis

• Of the effective calcium compounds, all caused liquid yield loss (up to 30% loss) except for Ca(COOH)2

• In general, calcium compounds

• Convert catechols to phenols

• Cause increased alkylation

• Inhibit formation of anhydrosugars

• Produce cyclic ketones

Calcium Formate-Assisted Pyrolysis of Lignin

• Lignin has free hydroxyl groups which may act similarly to organic acids during neutralization/pyrolysis• Binding of these groups helps with feedstock

handling• Addition of calcium formate provides hydrogen for

“deoxyhydrogenation”Lignin Lignin + 50 wt% formic acid Lignin + 100 wt% formic acid

Liquid Yield 23.0% 28.5% 32.5%

O:C ratio 0.19 0.14 .067

H:C ratio 0.96 1.23 1.40

HHV 30.7 37.2 41.7

Mukkamala, S. et al. Energy & Fuels (2012)

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Lignin Summary

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LigninCatechols

Phenols

PAH

Untreated

Ca(COOH)2 treated

CaO treated

Phenols from FAsP Lignin Oil

• Fraction of phenols and alkylated phenols in oil

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Compound wt %

phenol 3.90%

1,2-benzenediol 2.60%

2-methyl phenol 1.60%

3-methyl phenol 2.60%

4-methyl phenol 2.60%

3-methylbenzene-1,2-diol 3.20%

4-methylbenzene-1,2-diol 0.00%

2-ethylphenol 0.10%

2,5-dimethylphenol 0.80%

2,4-dimethylphenol 0.50%

3,5-dimethylphenol 0.40%

2,6-dimethylphenol 0.20%

3,4-dimethylphenol 0.40%

4-ethylbenzene-1,2-diol 1.80%

4-ethylphenol 0.90%

2,3,5-trimethyl phenol 0.10%

Total 21.70%

Phenolics Extraction from Lignin Oil

Vithanage, A., Gramlich, W. et al., submitted for publication

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phenol compound Lignin FAsP oil Extract Mimic

Phenol 3.90% 10.00% 21.90%2-methyl phenol 1.60% 6.00 11.80%3-methyl phenol 2.60% 11.20% 21.20%

4-methyl phenol 2.60% 8.90% 18.40%2,5-dimethylphenol 0.80% 3.50% 6.70%

2,4-dimethylphenol 0.50% 6.40% 11.70%3,5-dimethylphenol 0.40% 1.40% 2.60%

2,6-dimethylphenol 0.20% 0.70% 1.70%3,4-dimethylphenol 0.40% 2.00% 3.90%

A mimic composition was prepared for Novolac resin synthesis based on extract composition

Novolac Resin Synthesis

• Alkyl substitution increased degree of polymerization in resin

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Cross-Linking Resins with HMTA

• Stronger cross-linking without alkyl groups

• Mimic of the extracted phenols improved cross-linking over raw oil

• Material comparable to phenol resins possible with adjusting f/p

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Conclusions

• Calcium formate provides an active source of hydrogen during pyrolysis

• Calcium formate can be produced from pyrolysis process by-products

• Calcium formate assisted pyrolysis of lignin produces a phenolic-rich oil

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Acknowledgements

• Page Pomeroy• Saikrishna Mukkamala• Scott Eaton• Adriaan van Heiningen• Brian Frederick• Mayank Patel• Chi Truong• Nate DeSisto• Jake Koffman• U.S. Department of Transportation #DTRT13-G-UTC43 through

Maine Maritime Academy• SEP Integrated National Framework for Cellulosic Drop-in Fuels

Grant # 1230908

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