Different selections of active sites for CO, C3H6, and C10H22 oxidation on Pd/CeO2 catalysts

In this work, the catalytic conversion for the mixture of CO, C3H6, and C10H22 was investigated over 1-7 wt.% Pd/CeO2 (1-7 PC-h, where "-h" indicates the hydrothermal aged sample) catalysts. As Pd loading increases, only the performance for CO and C3H6 oxidation has been improved, while the C10H22 conversion is decreased. For Pd/CeO2 catalysts, its activity for the three major contaminants is sites dependent. We found that the cationic small Pd clusters (similar to 2 nm) favor C10H22 oxidation. Differently, the exposure of the metallic Pd atoms favors CO and C3H6 oxidation. Furthermore, C10H22 conversion on 3-7 PC-h is hindered by the presence of CO2 and C3H6, while the reaction on 1 PC-h is not influenced. This induces a lower C10H22 conversion on the samples with higher Pd content. CO2 is not the main reason since the surface basicity is not significantly changed. Meanwhile, the presence of C3H6 is the main reason, which hinders C10H22 oxidation except on 1 PC-h. This is explained by the reaction competition of C3H6 on the large Pd particles (>3 nm), where C10H22 was not able to get fully converted. (C) 2012 Elsevier Ltd. All rights reserved.