Effect of Ni Loading on Catalyst Bed Temperature in Oxidative Steam Reforming of Methane over (alpha)-Al2O3-Supported Ni Catalysts

Temperature profiles and catalytic performance over (alpha)-alumina-supported nickel catalysts with various Ni loadings (0.2-10 wt %) were studied during the oxidative steam reforming of methane. The catalyst bed temperature during the reaction was dependent on the Ni loading amount. From the viewpoint that the formation of hot spots can be inhibited to some extent, 0.9 wt % Ni was a suitable catalyst in our case, which exhibited the lowest bed temperature at W/F = 0.4 g·h/mol. To investigate the factors that control the bed temperature during the oxidative steam reforming of methane, first, the steam and CO2 reforming of methane was carried out. It was found that the methane conversion gradually increased with increasing Ni loading. Second, the catalytic behavior was examined when the reforming gas (CH4/H2O) was added to the combustion gas (CH4/O2). The results revealed that over the catalyst with lower Ni loading, the combustion activity was rather low; however, the combustion activity and the catalyst bed temperature were drastically enhanced in the presence of the reforming gas. Moreover, the correlation between the bed temperature in oxidative steam reforming of methane and catalytic performance of methane combustion and methane reforming was stated. Furthermore, we also carried out catalyst characterization by means of X-ray diffraction, temperature-programmed reduction with hydrogen, and measurement of adsorption amount of hydrogen. On the basis of characterization results, the effect of Ni loading on the oxidative reforming of methane was discussed.