Effect of Y2O3 and Nd2O3 on the Steam Reforming of Methanol Over Cu/ZnO Catalysts

The production of H-2 by the steam reforming of methanol (SRM) over Y2O3-or Nd2O3-promoted Cu/ZnO catalysts has been investigated. The additives effectively increased both the activity and the CO2 selectivity of the catalyst over the temperature range studied with the effect being superior for Nd2O3. The promoters also increased the available metallic Cu surface area of the catalyst. Although the results of the temperature-programmed reduction and X-ray photoelectron spectroscopy studies suggested that the chemical environments of the Cu species were altered by the addition of both Nd2O3 and Y2O3, the mechanisms of promotion were deduced to be different. The Y2O3 functioned mainly by acting as a separator to improve the dispersion of Cu, but it could also affect the active sites of the catalyst to some extent. In comparison, Nd2O3 not only improved the dispersion of Cu but also affected the catalytic behavior of the active sites. Kinetically, the additives served to increase the rate of the rate-determining step, with a concomitant decrease in the adsorption capacity of the catalyst toward the reactants. Moderate addition of the studied promoters resulted in the best catalytic activity in the SRM process.