Low-Temperature Oxidation of Methane over Pd Supported on SnO2-Based Oxides

Abstract

Abstract Pd catalysts supported on various metal oxides were investigated for the low-temperature catalytic combustion of methane. Of the catalysts examined, a Pd/SnO2 catalyst demonstrated excellent activity despite its low specific surface area. The activity of the Pd/SnO2 catalyst was lowered with the addition of M ( = Al, Ce, Fe, Mn, Ni, and Zr) oxide to the support, Pd/SnO2–MOx. It was observed by a transmission electron-microscope observation that the PdO phase was well-dispersed on the outer surface of SnO2support uniformly, observed as an intimately contacted layer on fine SnO2 particles. The temperature-programmed desorption of oxygen has revealed that the catalytic activity depends on the adsorption state of oxygen on palladium. An X-ray photoelectron spectroscopic analysis suggested that reduction of the palladium surface proceeded slowly under a strong palladium-support interaction for Pd/SnO2. In situ X-ray diffraction indicated that the PdO phase was stabilized at higher temperature on SnO2 than on the Al2O3 support. It is considered that the catalytic activity is strongly influenced by the interaction between palladium and SnO2.