Low-Temperature Deactivation and Oxidation State of Pd/γ-Al_2O_3 Catalyst for Total Oxidation of N-Hexane

摘要

The catalysts typically used for VOC incineration are noble metals such as platinum or palladium. Even if the palladium catalysts have been widely applied for the combustion process for VOC removal, the effects of oxidation state of palladium on the catalytic activity are still under debate. It is now widely accepted that a Pd-based catalyst supported on alumina can readily undergo oxidation/reduction transformations and these transformations can lead to rapid changes in apparent catalyst activity. There is a general consensus that PdO/Al_2O_3 is more active than Pd/Al_2O_3 for high-temperature combustion of methane. Recent studies, however, have shown that supported metallic palladium catalyst was more active than oxidized palladium for combustion of some VOCs. In the present work, the oxidation of n-hexane was carried out over Pd/γ-Al_2O_3 catalysts. The effects of different pre-treatments(oxidation/reduction) on the catalytic activities were investigated by obtaining light-off curves and also through temperature-programmed surface reaction (TPSR). The change of oxidation state was analyzed with XPS, and the nature of low-temperature deactivation was investigated through TGA and TPO.