Complete catalytic oxidation of methane over Pd/CeO₂-Al₂O₃: The influence of different ceria loading

Five kinds of mixed supports of CeO₂-Al₂O₃ were prepared by sol-gel method by varying the amount of ceria in the support from 2 to 50 wt.%. These supports were impregnated with palladium nitrate in order to obtain the catalytic samples. The effect of different ceria loading on Pd/CeO₂-Al₂O₃ catalysts and supports was investigated by physical characterization such as surface area measurements and XRD analysis. Additionally, TPR profiles of supports and Pd-containing catalyst were recorded. Reduction of surface area was observed for samples with high amount of ceria. For catalytic support with the highest ceria loading well crystallized ceria was observed whereas the other samples showed amorphous phases. TPR results have evidenced the enhancement of reduction of ceria in the supports by addition of precious metal although reduction of catalytic samples requires higher temperature as the amount of ceria in the support is higher. The results of oxidation of methane over Pd/CeO₂-Al₂O₃ confirm the suppression of the catalytic activity for samples containing high ceria loading, although such degree of depression depends also on cerium oxides present in the catalytic support.