Mechanistic Study of Carbon Dioxide Reforming with Methane over Supported Nickel Catalysts

Abstract

Carbon dioxide reforming with methane to synthesis gas has been investigated in terms of the effects of active metal loading, feed ratio, and reaction temperature on catalyst activity and stability employing supported Ni, Co, and Fe catalysts. Temperature-programmed desorption, temperature-programmed surface reaction, and X-ray photoelectron spectroscopy experiments were conducted to elucidate the reaction mechanism. An interesting observation made was that the direct dissociation of methane without the involvement of adsorbed or gas-phase CO2 most likely occurs and that the formation of hydrogen and surface carbon species, which are both primary products of the decomposition of methane, is the key step for the reforming reaction. Carbon monoxide might be the secondary product formed by interaction between surface carbon species and gas-phase or adsorbed CO2. Three surface carbon species Cα, Cβ and Cγ, which are produced by the decomposition of methane, showed various mobility, thermal stability, and reactivity. In the meantime, the residual partial oxidative NiOx species that were not thoroughly reduced could not migrate on the catalyst surface and be stepwise reduced during the reaction.