PdO-CeO2 Composite Catalysts for Low Temperature CO Oxidation

A series of PdO-CeO2, composite catalysts were prepared using a co-precipitation method and tested for low temperature CO oxidation. The catalysts were further characterized by X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET) technique, chemisorption of CO, temperature programmed reduction (TPR), and a pulse reaction technique. Results of XRD indicated that CexPd1-xO2-delta solid solution was formed when the catalysts were calcined at 400-800 degrees C, while PdO or metal Pd species re-migrated to the catalyst surface when it was calcined at a higher temperature (1000 degrees C). The turnover frequency (TOE) for the CO oxidation reaction over these catalysts was found to be independent on the Pd particle size and it increased with increasing the content of CexPd1-xO2-delta solid solution in the catalyst. This suggests that the solid solution might be the active phase for the reaction. Furthermore, pulse reaction results indicated that oxidized Pd species were more active than metallic Pd.