CO2 reforming of methane over vanadia-promoted Rh/SiO2 catalysts

The reforming of methane with carbon dioxide over rhodium dispersed on sili ca, Rh/SiO2, and vanadia-promoted silica, Rh/VOx/SiO2, was studied by kinet ic test reactions under differential conditions in a temperature range from 723 to 773 K. Transmission infrared spectroscopy was applied to observe th e interaction of CO2 with the catalysts and the formation of surface interm ediates during the CO2-CH4 reforming reaction. To analyze carbon deposition XP spectroscopy and TPO was carried out. It has been shown that the promot ion of Rh/SiO2 catalysts with vanadium oxide enhances the catalytic activit y for CO2 reforming of methane and decreases the deactivation by carbon dep osition. This is attributed to the formation of a partial VOx overlayer on the Rh surface, which reduces the size of accessible ensembles of Rh atoms required for coke formation and creates new sites at the Rh-VOx interfacial region that are considered to be active sites for the activation/dissociat ion of carbon dioxide.