Mechanism of the Steam Reforming of Methane over a Coprecipitated Nickel-Alumina Catalyst

Abstract

The kinetics of the steam reforming of methane over a coprecipitated Ni/Al2O3 catalyst have been examined in the temperature range 773 to 953 K and in the pressure range 0-10 Torr. Examination of the stoichiometry of the reaction showed that a catalyst freshly reduced in hydrogen at S73 K was further reduced by the reaction mixture. This is taken to imply that reduction of some phase such as NiAl2O4 was occurring. The rate determining step of the reaction on the fully reduced catalyst under reducing conditions was found to be the rate of adsorption of methane and competition for the adsorption sites by water occurred. The water-gas shift reaction did not proceed appreciably, and this implies that significant CO and CO2 adsorption does not occur on the catalyst surface ; this is in agreement with the kinetic results. Experiments involving D2O or D2 helped to confirm these conclusions.