Transient isotopic studies and microkinetic modeling of methane reforming over nickel catalysts

The kinetics of elementary surface reactions involved in the reforming of methane to synthesis gas over supported nickel were studied using transient isotopic methods. To investigate methane adsorption and dehydrogenation, the reaction between CD4 and H-2 was studied. To investigate water adsorption and dissociation, the reaction between H2O and D-2 was studied. To investigate the formation and cleavage of C-O bonds on the nickel surface, transient CO methanation experiments were performed. Rate constants of surface elementary reactions were extracted from the data by fitting the measured response curves to microkinetic models. An overall model that describes the reactions of methane with steam and CO2 in microkinetic terms was constructed based on these rate constants and on previously published steam reforming and CO2 methanation data. The model suggests that there is no single rate-determining step in methane reforming with either steam or CO2, and that under some conditions the availability of surface oxygen may play a key role in determining the rate. (C) 1997 Academic Press