Presentation Identifier (Title or Location), Month 00, 2008
Structured Oxide-Based Reforming Catalyst Development
11th Annual SECA Workshop, Pittsburgh, PAJuly 29, 2010
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Introduction• Reform HCs into H2 and CO-rich gas stream for solid
oxide fuel cell (SOFC) applications
Diesel
Fuel
ProcessorSyngas
SteamFC
Stack
Reforming TechnologiesPower
Fuel Cell Systems
Applications
Fuel
Syngas (H2, CO, CH4...)
Plasma
• Stationary• Military• Transportation
Coal
Fuel Sources
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Primary Goal
Identify, evaluate and/or develop viable hydrocarbon fuel processingtechnologies for high temperature solid oxide fuel cells being supported inthe NETL SECA program through fundamental understanding, research,and technology demonstration.
Fuel Technology End Use
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Two Project Areas
Oxide-Based Catalyst Systems:
Apply fundamental understanding of fuel reforming & deactivation mechanisms into intelligent design of alternative catalyst systems for long-term, stable hydrogen-rich synthesis gas production.
Advanced Reforming Concepts:
Identify and evaluate alternative non-catalytic and/or catalyst assisted processes to overcome deactivation of traditional catalytic fuel reforming of higher hydrocarbon fuel compounds.
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Structured Catalyst Development• Objective: Apply fundamental understanding of fuel reforming &
deactivation mechanisms into design of alternative catalyst systems for long-term, stable hydrogen-rich synthesis gas production.
• Technical objectives / challenges
• Reforming catalyst formula development
• Reforming studies with diesel surrogate fuel
• Oxygen-conducting support studies
• 1000-hr OSR demonstration test on pump diesel
• Development of commercially viable catalyst structure (monolith)
• Short-term OSR studies with diesel fuel on catalyst monolith
• 100-hr OSR demonstration test with biodiesel in integrated fuel cell test
• Graded bed approach
• RF-assisted catalytic reforming
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Reformer Integration
FuelReformer
FuelCell
Stack
Cathode
Anode
Q
Air
Fuel
Reforming Options: POx
Steam Reforming
Oxidative SR
Steam
Q
22mn H2mnnCOOnHHC
++→+Steam Reforming - Endothermic
Q
( ) 2222mn N2n3.76H
2mnCO3.76NO
2nHC
++→++POx Reforming - Exothermic
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• Desired Thermal Integration with Fuel Cell – Similar Temperature of Operation:
Reduces unnecessary heat exchange and can increase system efficiency – cost & complexity savings.
Challenges: Thermal processes require too high temperatures. Can be achieved by utilizing catalysts to lower reformation temperatures. Unfortunately, most hydrocarbon fuels contain sulfur and complex hydrocarbons that deactivate catalyst systems prematurely. Commercial catalysts developed mostly for natural gas reformation & naphtha.
• Possible Low or Waterless Operation: Reduces or eliminates the complexity and cost of managing water
within the system. Some applications cannot consider water addition to the process.
Challenges: The use of water (usually excess) is the principle combatant to carbon formation for commercial catalysts. Water however can also increase system efficiency by increasing hydrogen concentration via steam reforming & heat utilization: Cost vs efficiency trade-off.
Technical Objective / Challenges
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Evolution of NETL Reforming Catalyst System
(1&2)
(3)
(1-3)
(1) Support sintering
(2) Sulfur poisoning
(3) Coke formation
Metal Particles Substituted into a Thermally Stable Oxide
Metal Particles Substituted into a Stable Oxygen-
conducting Oxide Metal Particles/
Metal Particles/
Oxygen-conducting
Metal Particles Substituted into a Stable
Oxide/OCS
Metal Particles Substituted into a Stable Oxide/
OC-film/High SA Support
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Oxide-based Catalyst Systems (Pyrochlores)
Doping the lattice of certain oxide-based compounds with catalytic metals results in…A structured catalytic surface with nano-sized metallic crystallites that serves as a template to control metallic crystallite size and dispersion.
A-site cationB-site cation
Oxygen anion
Pyrochlores (A2B2O7) are viable reforming catalysts because they exhibit: • High chemical and thermal stability [1]• Mechanical strength to accommodate
substitutions [2]• Active metal can be substituted into B-site to
improve catalytic activity • Substitution with lower valence elements in A-site
and B-site can create oxygen vacancies, which may increase lattice oxygen-ion mobility to reduce carbon formation.
[1] D. Sedmidubsky, et al., The Journal of Chemical Thermodynamics 37 (2005) 1098.[2] H. Zhou, et al., Journal of Alloys and Compounds 438 (2007) 217
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Micro-Reactor Setup
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Experimental conditions T=900 C, P= 0.25 MPa, GHSV= 50,000 sccm/g-hr
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300 350
Time on stream (min)
Yiel
d (%
)
LSRZ
Rh/γ-Al2O3
5 wt% 1-MN & 1000 ppmw S added
5 wt% 1-MN & 1000 ppmw S removed
Pyrochlore for POx of Diesel Surrogate
A conductive oxide-based catalyst was doped with 1% Rh along with a SOA Rh catalyst on alumina. After exposure to a severely carbon producing fuel compound, the oxide-based catalyst performance remained stable, while the non-conducting supported catalyst deactivated significantly.
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Oxide Catalyst on Oxygen-Conducting Supports
Metal OxideCatalyst
Oxygen Conducting Catalyst Support
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1000-hr Demonstration of Pyrochlore Catalyst for Oxidative Steam Reforming of Pump Diesel
0
100
200
300
400
500
600
700
800
900
0
5
10
15
20
25
30
0 200 400 600 800 1000 1200
Ole
fins
Pro
duce
d (p
pm)
Com
posi
tion
(%)
Time on stream (hrs)
HydrogenCarbonMonoxideCarbonDioxideMethaneOlefins
H2
CO
CO2Olefins= ethylene + propylene + C4-ene + benzene
Water pump off Water
pump on
Fully reformed local pump diesel Equilibrium syngas yields achievedSurvived multiple system upsets O/C=1, H2O/C=0.5, T=900 C, P= 0.25 MPa, SV= 25,000 sccm/g-hr
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• Fabrication of Catalyst into a Commercially Viable Structure
• Powder Catalyst Validation:• Activity tests; TPO (carbon formation)• Bulk characterization – ICP, XRD
• Surface characterization – XPS, TPR, H2-chemisorption• Preliminary Tests on Coated Monolith
NETL’s Pyrochlore Catalyst in Powder
Form
Monolith Coated by NexTech
Microlith® Technology by
PCI
Diesel Fuel Reforming using Pyrochlore CatalystCollaboration with Industrial Partners
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Monolith Reactor Coated with Pyrochlore Catalyst
• NETL-developed Pyrochlorecatalyst deposited onto alumina monolith with oxygen-conducting interlayer
• Coated using proprietary method by Nextech Materials, Inc.
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Coated Monoliths from NexTech
Base Support: 400 cpi alumina-based
Coated Monolith: Incorporates NETL pyrochlore catalyst system
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Successful Operation of a Solid Oxide Fuel Cell Fueled with Syngas from Biodiesel Reforming
• Biodiesel was reformed for 100 hrs on a pyrochlore catalyst supported on a monolith
Biodiesel Reformer 0
5
10
15
20
25
30
35
40
45
50
16-Nov 17-Nov 18-Nov 19-Nov 20-Nov 21-Nov
Perc
ent C
ompo
sitio
n
Syngas Composition versus Time
Hydrogen
Carbon Monoxide
Carbon Dioxide
Methane
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Pyrochlore for Natural Gas Steam ReformingS/C = 0.9; TRXR = 700 C; GHSV = 25,000 scc/gcat•hr
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Graded Catalyst Bed Approach
Combustion
SR + WGS
Steam Reforming
~1100oC
CO2Reforming
+
High AromaticConcentration
~700oC
900oC
Low TempSulfur Poison
Rh-Pyrochlore
Ni, Pt, Ru-Pyrochlore/
Ni-HxAl
CombustionCatalyst
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0
5
10
15
20
25
0 60 120 180 240 300
Hyd
roge
n Co
ncen
trat
ion
(%)
Time (min)
0.49g C
0.71g C
1.13g C
1.88g C
1.41g C
1.31g C
Rh-Pyrochlore(LCRh1ZY)
Ni-Hexaaluminate(BNHA)
Preliminary Results: BNHA/LCRh1ZY
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Energy bands of atoms or molecules absorb the RF energy
Localized heating of the material at the rxn site with higher dielectric loss index and
excitation of valence electrons
Lowers the activation energy required for desired chemical
reactions
Functions as an enhanced catalyst
Alternative Reforming ConceptsRadio-Frequency Enhanced Reaction Concept
RF Antenna
Fuel & Air (in)
H2 & CO (out)
T=900C
Furnace
Catalyst
bed
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50
55
60
65
70
75
80
85
0 1 2 3 4 5
H2 Y
ield
(%)
Time (hrs)
Baseline20W40W60W80W100W
50
55
60
65
70
75
80
85
0 1 2 3 4 5C
O Y
ield
(%)
Time (hrs)
Baseline20W40W60W80W100W
Alternative Reforming ConceptsRadio-Frequency Enhanced Reaction Concept
• Effect of RF power on Syngas yields at fixed frequency (13.6 MHz)• Preliminary results suggest that applied RF field has a positive influence on reforming• Also see a slight reduction in carbon (coke) formation on the catalyst bed when RF field
is applied• Further testing in underway to repeat these findings and understand the underlying
mechanism of enhanced catalyst activity
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Summary/Conclusions
• SOFC-based APUs for commercial diesel trucks is an excellent market entry technology– Reforming catalyst with long-term stability and performance is
critical for successful demonstration of transportation application
• Pyrochlore catalyst on oxygen-conducting support successfully reformed pump diesel for 1000-hr
• Optimized pyrochlore catalyst applied to commercially representative structured supports– Preliminary performance of catalyst monolith demonstrated
on pump diesel and biodiesel fuels under oxidative steam reforming
• Preliminary RF experiments have shown some evidence of reduced carbon formation and enhanced catalyst activity
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NETL Fuel Processing Team
• David Berry• Dushyant Shekhawat• Nick Siefert• Dan Haynes• Mark Smith• Mike Gallagher• Don Floyd• Mike Bergen• Prof. Jerry Spivey (LSU)
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Acknowledgements
• SECA• NexTech Materials