Hydrogenation of CO to methane: kinetic studies on polycrystalline nickel foils

Abstract The existence of a transition in the activation energy of the methanation reaction, a decrease in the activation energy with increasing H 2 /CO ratio below the transition, a shift of the transition to lower temperature with increasing H 2 /CO ratio, and the existence of a kinetic isotope effect for the reaction at low pressure and high H 2 /CO ratio have been shown. This kinetic behavior can be understood in terms of the temperature and partial-pressure dependence of the hydrogen adatom surface concentration. The observation of a kinetic isotope effect and the correlation between the kinetic behavior of the calculated hydrogen adatom surface concentration and the observed kinetics of the methanation reaction suggest that the methanation reaction over nickel is a hydrogen adatom surface concentration-limited reaction.