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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
-150.00
-100.00
-50.00
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Minutes
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00
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 -
18.7
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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1.20
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
0.00
0.05
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400 450 500 550 600
Temp. (oC)
CO
2 se
lect
ivity
3%Rh3%Pt/CeZrO23%Rh1%Pt/CeZrO23%Rh/CeZrO2
1.000
1.500
2.000
2.500
3.000
3.500
4.000
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
0.10
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0.30
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0.50
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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
0.500
1.000
1.500
2.000
2.500
3.000
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
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