Integrated Micropower Generator Catalyst Optimization

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

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!!