The Influence Of Ceria-Zirconia On Pd Catalysts For Methane Partial Oxidation To Synthesis Gas

With the gradually depletion of fossil energy, a great deal of interest has grown in using natural gas as high quality, clean energy and chemical raw. Methane partial oxidation is weak exothermic and the process needs less energy and capital cost than the conventional endothermic steam reforming. Moreover, the reaction rate is very fast and the H2: CO ratio of about 2 is suitable for downstream processes such as Fischer-Tropsch synthesis. So the methane partial oxidation is paid much attention in recently years.In this paper, mixing supports CeO₂-ZrO₂/Al₂O₃ with three different mixing methods were prepared by co-precipitation method and theα-Al₂O₃, CeO₂-ZrO₂ and CeO₂-ZrO₂/Al₂O₃ supported Pd catalysts were prepared by impregnation method. The catalytic performance of methane partial oxidation was investigated on Pd/α-Al₂O₃, Pd/CeO₂-ZrO₂ and Pd/CeO₂-ZrO₂/Al₂O₃ catalysts. The influence of Pd loading, calcaning temperature and supports effect on the catalytic performance was compared on Pd/α-Al₂O₃ and Pd/CeO₂-ZrO₂ catalysts. The effect of mixing support and mixing methods on the catalytic performance was also studied. Catalysts were characterized by XRD, BET, TPR, Raman spectra and TG-DTA techniques.The results indicate that CeO₂-ZrO₂ supporter may reduce the Pd loading content and CeO₂-ZrO₂ supported catalyst takes on higher catalytic performance and stability, which might be attributed to the better dispersion of Pd and oxygen storage capacity of CeO₂-ZrO₂. Among the three Pd/CeO₂-ZrO₂/Al₂O₃ sampls, molecular mixing sample behaves the higher stability, this might be explained by stonger intereaction between Pd and support, and larger interface between metal and CeO₂-ZrO₂. Metal sintering and carbon deposition are the main reason for the deactivation of catalysts after 24h reaction. Carbon deposited on the catalysts is in the form of graphite and mostly deposited on the acid sites of the supports.