New data on gas-phase radical reactions in the steam reforming of methane in the presence of catalysts: I. Nickel catalysts

Article abstract of DOI:10.1007/BF02756135

Methane pyrolysis and steam reforming were investigated over various nickel-containing catalysts, i.e., Ni/Al₂O₃, Ni/MgO, and Ni/LiAlO₂, at 650°-750°C and 0.001-0.03 MPa. Some of the steps of methane steam reforming occurred in the gas phase compared with heterogeneous reaction of pyrolysis. A change in the filling of the reactor with the catalyst affected the rate and the value of the apparent activation energy of the process. The rate and activation energy of steam reforming were close to the corresponding kinetic characteristics for pyrolysis when gas-phase reactions were suppressed. An increase in the catalyst loading and/or the addition of an inert sorbent that adsorbs active radicals from the gas phase decreased the apparent rate constant and the activation energy because of the suppression of gas-phase radical reactions, which is characteristic of the transition from a heterogeneous-homogeneous to a purely heterogeneous mechanism. It was supposed that the rate of the process is determined by methane adsorption on nickel with the formation of adsorbed hydrogen and methyl.