Aqueous Phase Catalyzed Biomass Gasification

This presentation does not contain any proprietary or confidential information

Aqueous Phase Catalyzed Aqueous Phase Catalyzed Biomass GasificationBiomass Gasification

This presentation does not contain any proprietary or confidentiThis presentation does not contain any proprietary or confidential informational information

David L. King and Yong WangPacific Northwest National Laboratory

2004 DOE OHFCIT Peer ReviewMay 25, 2004

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Objective of WorkObjective of WorkObjective of Work

Develop a cost-effective method for the conversion of biomass feedstocks to hydrogen

Ethanol, PG, EG, glycerolSugars, sugar alcohols (xylitol, sorbitol, glucose)Less refined starting materials such as cellulose, hemicellulose

Provide technical and economic comparison with alternate biomass conversion approaches

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Project BudgetProject BudgetProject Budget

New start FY2004Two separate projects consolidated into single project for total of $100K funding

Aqueous phase gasification ($50K)Microchannel reforming ($50K)

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Technical Targets and BarriersTechnical Targets and BarriersTechnical Targets and Barriers

Cost and efficiency targets as defined by DOE2010 central hydrogen from biomass, total: $2.90/kg H2

2010 reforming cost ~$1.90/kg H2

Combined gasification plus reforming efficiency = 67% Hydrogen production from biomass barriers (3.1.4.2.2)

“F” Feedstock cost and availabilityImproved technology for production, collection, transportation, storage and preparation of feedstocks

“G” Efficiency of gasification, pyrolysis and reforming technologyCatalysts, heat integration, reactor configuration, feedstock handling, gas cleanup

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Aqueous Phase Reforming Has Potential Advantages Over Conventional Reforming

Aqueous Phase Reforming Has Potential Advantages Aqueous Phase Reforming Has Potential Advantages Over Conventional Reforming Over Conventional Reforming

Compatible with wet or water-soluble feedstocksConventional steam reforming incompatible with sugars and sugar alcohols

Eliminates need to vaporize water for reformationImproved capability to reform without concomitant reactant decomposition and carbon formationLow CO byproduct due to facilitated water gas shift High pressure operation compatible with subsequent hydrogen purification

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Challenges of Aqueous Phase ReformingChallenges of Aqueous Phase ReformingChallenges of Aqueous Phase Reforming

Reactor volumetric productivity must be competitive with other biomass conversion technologiesSelectivity toward hydrogen production is challenging

H2, CO thermodynamically unstable relative to CH4, alkanesReactor configuration can have impact on selectivity

Catalyst deactivation and reactor fouling must be minimized

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Steam Reforming Using Microchannel Reactors Complements Aqueous Phase Reforming

Steam Reforming Using Steam Reforming Using MicrochannelMicrochannel Reactors Reactors Complements Aqueous Phase ReformingComplements Aqueous Phase Reforming

Improved heat and mass transfer significantly enhances reactor productivityEfficient thermal management and unit integrationMay offer best approach for

Fermentation-derived aqueous ethanol Glycerol (bio-diesel byproduct)Partially processed black liquor – PG, EG

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Recent Work Indicates Promise for Aqueous Phase Gasification1

Recent Work Indicates Promise for Recent Work Indicates Promise for Aqueous Phase GasificationAqueous Phase Gasification11

Catalysts and reactorsPrecious metals Pt, Pd best for hydrogen productionRh, Ru, Ni tend to form methane, alkanesRaney Ni + Sn dopant—reduces methanation activity of Ni

FeedstocksGlucose, sorbitol, glycerol, ethylene glycol, methanolHigher carbon number feedstocks have increased tendency for alkane formationFixed bed reactor to minimize series reactions

Increasing temperature leads to greater production of alkanes, potential for undesirable side reactions

1 R.D. Cortright et. al. Nature, vol 418, 29 August 2002; J.W. Shabaker et. al., J. Catalysis 215 (2003) 344; G.W. Huber et. al. Science vol 300, 27 June 2003.

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Reactor Productivity Reactor Productivity Reactor Productivity

“Weisz window” provides rule-of-thumb regarding required reactor productivity for chemical processes

Most chemical processes have reactor productivity 1x10-05 - 1x10-06

gmol reactant converted/cc-secHigher productivity limited by mass and heat transferLower productivity may be uneconomic

Recently reported activity of Pt/Al2O3 with sorbitol ~1x10-07 mol sorbitol converted / cc-sec at 383K~1.24x10-6 mole H2 produced /cc reactor-sec at low conversionAn order of magnitude increase in activity may be necessary for an economic aqueous phase gasification process

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Technical ConceptTechnical ConceptTechnical ConceptSynergistic aqueous-phase reforming and microchannel steamreforming to produce hydrogen from biomass

Feedstock flexibility with aqueous phase reformingEfficient steam reforming with microchannel reaction technology

Aqueous Phase

Reforming

Micro-channel Steam

Reforming Separation

Tail Gas (heat)

H2

Biomass wasteBlack liquorHemicelluloseCelluloseSorbitolXylitol

EthanolGlycerolPG, EG

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Technical ApproachTechnical ApproachTechnical ApproachAqueous phase gasification

Select xylitol as model feedstock which is difficult to steam reformEvaluate catalyst candidates via combinatorial/high throughput screening approachMaximize activity toward useful gas phase products: H2 plus hydrocarbonsSelect best catalysts for further reactor studies

Microchannel steam reformingDemonstrate the efficient steam reforming of the effluent from aqueous phase gasification of xylitolCompare microchannel vs. conventional steam reforming of ethanol

Combine aqueous gasification with microchannel steam reforming

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Combinatorial-High Throughput Screening of Aqueous Phase Gasification Catalysts

CombinatorialCombinatorial--High Throughput Screening of High Throughput Screening of Aqueous Phase Gasification CatalystsAqueous Phase Gasification Catalysts

Current equipment provides qualitative comparisons of catalyst performance

Liquid phase analysis (no gas phase sampling)—activity based on depletion of starting material

Xylitol gasification: testing protocols200oC (maximum temperature of operation)5% xylitol in waterCatalyst charge: 5 wt.%Metal loading on support: 3 wt.%Gas overhead: 5%H2/95%N2 at 500 psi (initial)Reaction duration: 4 hoursAnalysis: hplc

Preliminary findingsRu most active of group VIII metalsTiO2 (rutile), carbon most effective supports for gasification

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Combinatorial/High Throughput Screening Facilitates Identification of New Catalysts

Combinatorial/High Throughput Screening Combinatorial/High Throughput Screening Facilitates Identification of New CatalystsFacilitates Identification of New Catalysts

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Combinatorial/High Throughput Screening Shows Catalyst Differences

Combinatorial/High Throughput Screening Combinatorial/High Throughput Screening Shows Catalyst DifferencesShows Catalyst Differences

MV

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Glu

cose

-9.

217

Xyl

itol -

11.4

96

Ery

thrit

ol-1

2.13

8Th

reito

l-12

.473

Lact

ic A

cid

-12.

971

Gly

cero

l -13

.776

1,2,

4-B

utan

etrio

l -14

.598

Eth

ylen

e G

lyco

l -16

.579

Pro

pyle

ne G

lyco

l -17

.599

2,3-

But

aned

iol -

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83

1,3-

But

aned

iol -

19.6

25

1,2-

But

aned

iol -

21.1

42

Eth

anol

-22

.469

100261 H9 Xylitol Blank

100262 G2 Pt/TiO2

100262 C9 Ru/ZrO2100262 F9 Ru/TiO2

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Microchannel Steam ReformingMicrochannelMicrochannel Steam ReformingSteam ReformingSteam reforming of methane (primary aqueous phase product) has been demonstratedSteam reforming of aqueous ethanol and glycerol

Fermentation derived ethanol has the potential to meet the H2 cost target ($1.50/kg)Bio-diesel byproduct glycerol has potential to be cost competitive ($0.10/lb)

Demonstrate the advantage of microchannel reactors

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• Pathways for the steam reforming of ethanol are complex

• Ethylene and methane are the potential intermediates

• Efficient ethanol steam reforming depends on the control of intermediate formation and their efficient reforming.

Cavallaro, Energy & Fuels, 14 (2000) 1195

C2H5OH = CH3CHO + H2 (1)C2H5OH = C2H4 + H2O (2)CH3CHO = CO + CH4 (3)CH4 + H2O = CO + 3H2 (4)C2H4 + 2H2O = 2CO + 4H2 (4’)CH3CHO + H2O = 2CO + 3H2 (4’’)CO + H2O = CO2 + H2 (5)

Ethanol Steam ReformingEthanol Steam ReformingEthanol Steam Reforming

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400 450 500 550 600

Temp. (oC)

EtO

H c

onve

rsio

n

3%Rh3%Pt/CeZrO23%Rh1%Pt/CeZrO23%Rh/CeZrO2

• Pt enhances EtOH conversion and selectivity to CO2, likely due to enhanced WGS.• Pt also increases the selectivity to CH4, likely due to increased decarbonylation• Further improvement in catalysts to minimize CH4 formation is needed.

Reaction conditions: GHSV = 75,660 cm3/gh, H2O/EtOH/N2 = 3.0/1.0/1.8

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lect

ivity

3%Rh3%Pt/CeZrO23%Rh1%Pt/CeZrO23%Rh/CeZrO2

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1.500

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450 470 490 510 530 550 570 590

Temp. (oC)

H2

prod

uced

/EtO

H F

ed

3%Rh3%Pt/CeZrO23%Rh1%Pt/CeZrO23%Rh/CeZrO2

0.00

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400 500 600 700 800 900

Temp. (oC)

CH

4 se

lect

ivity 3%Rh3%Pt/CeZrO2

3%Rh1%Pt/CeZrO23%Rh/CeZrO2

Effect of Pt Addition on Rh/CeO2-ZrO2Reforming of Ethanol

Effect of Pt Addition on Rh/CeOEffect of Pt Addition on Rh/CeO22--ZrOZrO22Reforming of EthanolReforming of Ethanol

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Reaction conditions: GHSV = 75,660 cm3/gh, H2O/EtOH/N2 = 3.0/1.0/1.8 Quartz tube fixed bed reactor vs. microchannel reactor

H2 productivity at low temperatures can be enhanced using micro-channel reactor due to efficient heat transfer.

Reforming of Ethanol Shows Advantage of Microchannel Reactor

Reforming of Ethanol Shows Reforming of Ethanol Shows Advantage of Advantage of MicrochannelMicrochannel ReactorReactor

Catalyst: 3%Rh-3%Pt/CeO2-ZrO2

Quartz tube reactor

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350 370 390 410 430 450 470 490 510 530 550

Reactor wall temp. (oC)

H2 p

rodu

ced/

EtOH

Fed

micro-channelwith dilutionw/o dilution

Quartz Tube Reactor

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ConclusionsConclusionsConclusions

Aqueous phase gasification provides attractive alternative for generation of hydrogen from biomass feedstocksPreliminary screening of catalysts indicate ruthenium as attractive candidate for production of gas phase productsSteam reforming of ethanol indicates two possible pathways:

Via ethyleneVia methane

Addition of Pt to Rh/CeO2-ZrO2 catalyst increases undesirable methane formation

More acidic supports will favor desired ethylene pathway

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Future WorkFuture WorkFuture Work

Scaled-up tests of most active aqueous phase gasification catalysts in slurry and fixed bed reactors

Process variable study with xylitol, sorbitolDetermine advantages, disadvantages of each reactor approach

Continue microchannel steam reforming studies of EtOHand glycerolVerify that conventional steam reforming of sorbitol and xylitol not feasible due to reactant instabilityDemonstrate efficient steam reforming of aqueous phase effluent in microchannel hardwareDevelop process economics for combined aqueous phase gasification/ steam reforming approach

Compare with alternate approaches based on pyrolysis + reforming

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Safety AspectsSafety AspectsSafety Aspects

Aqueous gasification work to date limited to small volume, high throughput mini-reactors

Each run employs 96 vials containing water, sorbitol, and catalystOverhead pressure for some runs of 200 psig of 5%H2 in N2, totalH2 volume (stp)~50 cc

Total combustion of H2 in system would lead to less than 200 psig increase in overall pressure

Reactor encasing rated at 1500 psigSystem enclosed in vented canopySystem appears safe

No safety-related events or issues encountered