1. Integrated Micropower Generator Catalyst Optimization
SOFC
Swiss Roll
Combustor +
High Efficiency
Thermal Management
Sossina M. Haile, Zongping Shao, Chan Kwak, Peter Babilo
California Institute of Technology, Materials Science

2. Propane Combustion Catalyst Testing
Materials/Conditions
Gas phase (empty)
‘Inert’ dispersant, SiO2
La0.2Sr0.8Co0.6Fe0.4O3 (LSCF), perovskite
Pt on SO4 modified ZrO2
Catalytic Reactor
Thermocouple
C3H8 + O2 + He or Ar
furnace
Catalyst dispersed in inert materials
GC analysis

3. Propane catalytic combustion
Gas phase propane combustion is negligible at temperatures lower than 600oC
No CO or H2 were produced for gas phase reaction
Propane combustion is the main reaction, propane oxidative dehydrogenation increases with increasing temperature

4. Propane catalytic combustion
‘Inert’ material is slightly active for propane combustion

5. Propane catalytic combustion
LSCF
1.Some perovskite type mixed conducting oxides have favorable catalytic activity for propane combustion at high temperatures
2. Propane conversion increases with increasing oxygen to propane ratio

6. Propane catalytic combustion
Pt5%wt.-ZrO2/SO42- catalyst has very high activity for propane combustion.
If not diluted, the heat produced can self-sustain the temperature for propane combustion
Light off temperature can be as low as 250oC
CO2 and H2O are the only products

7. Propane catalytic combustion
Propane conversion decreased with increasing oxygen to propane ratio, best ratio is 5.
Behavior is opposite that of the perovskite type catalyst

8. Propane catalytic combustion
Pt5%-ZrO2/SO42- catalyst is relatively stable under long term operation
Time dependence of propane combustion over Pt5%-ZrO2/SO42- catalyst
0.02g, 300oC, propane: 1ml/min, oxygen:5ml/min, helium: 200ml/min

9. Summary
Propane after-burner via catalytic combustion in a Swiss roll reactor quite feasible
Sulfated Pt supported on ZrO2 has very high activity for propane combustion
CO2 and H2O are the only products
In comparison, perovskite catalyst has lower catalytic activity, however, still considerably active
Perovskite LSCF unsuited for either after-burner catalyst or cathode

10. Where to go from here Reaction initiation for self-starting fuel cell
Use gas with low temperature light-off capability
Examples: CO, H2
Main consideration: Safety
Use O3:C3H8 ratio optimized for combustion initially
Incorporation of new catalyst into Swiss roll
Deposition of powders onto mechanical support
Establish quantity required
Development of cathode material with high oxygen reduction activity, but low propane combustion activity  key challenge!!