Abstract
A comparative study of catalytic CO oxidation and selective CO oxidation over Pt/Al2O3 and CeO2-promoted Pt/Al2O3 catalysts has been investigated for the removal of a trace amount of CO from the reformed gas. The catalysts were prepared by sol gel and incipient wetness impregnation. CO oxidation and selective CO oxidation were carried out with a 5%Pt/Al2O3 and a 5%Pt/15%CeO2/Al2O3. The presence of 15%CeO2 inthe 5%Pt/Al2O3 dramatically improves the activities to CO oxidation and selective CO oxidation at low temperature (<180℃). FTIR results indicate that CO could react with lattice oxygen from ceria and release CO2 as a product. Low space velocity would obtain high CO conversion at low temperatures while high space velocity would obtain high CO conversion at high temperatures. The results also show that a 5%Pt/15%CeO2/Al2O3 can completely oxidize 1% CO at180℃with selectivity of 52% and space velocity of70,000 cm3·g-1·h-1. Under the realistic gas feed with 1%O2, this catalyst is very stable and retains its activity and selectivity at180℃during 72 h.
Highlights
The polymer-electrolyte-membrane fuel cell (PEMFC) has been attracting significant attention in several applications including electric vehicles and residential powergenerations
As the PEMFCs utilize hydrogen gas as a fuel and since hydrogen can be produced by means of a fuel reformer followed by water gas shift reaction for further conversion of CO to H2, carbon monoxide is always present in the hydrogen stream
It has been found that the tolerable level of CO without harmful effects is about 10 ppm [5]. This means the 0.5%-1.0% CO needs to be reduced to 10 ppm or less in order to increase the use of proton exchange membrane (PEM) fuel cells running with on-board generated hydrogen
Summary
Parinyaswan et al [21] investigated the performance of Pt-Pd/CeO2 catalysts for selective CO oxidation This catalyst could maximally convert 83% CO to CO2 with selectivity of 60% at 90°Cwith a gas feed containing 1% CO, 1% O2, 25% CO2 and 10% H2O. In order to obtain a better understanding of the activity of the ceria promoted platinum alumina catalyst to the selective CO oxidation, 5%Pt/15%CeO2/Al2O3 and 5% Pt/Al2O3 catalysts were tested for their activities to both CO oxidation in H2 free-stream and CO oxidation in the presence of excess H2-containing feed stream and the obtained results were compared with others reported in literatures. The effect of space velocity on the activity of the catalyst was investigated These results will lead us to the proper operating conditions in order to obtain high selectivity and high CO conversion of ceria promoted Pt alumina catalyst
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