Pd and PdAu on mesoporous silica for methane oxidation: Effect of SO2

Palladium and gold–palladium catalysts supported on mesoporous silica were prepared by incipient wetness impregnation. They were characterized by XPS, XRD, BET, and FTIR acidity measurements. The activity was tested in the oxidation of methane under lean conditions. The effect of adding SO2 to the reactant mixture was investigated. Test reactions were consecutively performed to evaluate the thermal stability and poisoning reversibility. The palladium catalyst performed quite well in terms of the light-off temperature (T50<300T50<300 °C) and SO2 tolerance. Moreover, the activity, which decreased after a night treatment in SO2 at 350 °C, was completely recovered in subsequent cycles. The presence of gold decreased the activity slightly without altering the SO2 tolerance. Evidence of a dynamic reduction–oxidation process occurring at the palladium surface was obtained from the gold-promoted sample in which the reduction of palladium on SO2 treatment was ascertained.