Cu2O as active species in the steam reforming of methanol by CuO/ZrO2 catalysts

Steam reforming of methanol (SRM) was carried out at 250 °C over CuO/CeO2 and CuO/ZrO2 catalysts with various CuO contents and water/MeOH ratios in a flow reaction system. The 80 wt.% CuO/ZrO2 gave the highest activity, and the optimum water/MeOH ratio was 1.5. The oxidation states of Cu species in post-reaction catalyst depended upon CuO contents and the water/MeOH ratio. The starting copper compounds were CuO in all cases, and the copper in almost all catalysts was reduced to metallic Cu. Cu2O appeared in 80 and 90 wt.% CuO/ZrO2 when water/MeOH ratios were above 1 irrespective of reducing atmospheres. The reduction behavior of the 80 wt.% CuO/ZrO2 catalyst with hydrogen was investigated by XANES technique in an in situ cell. In the narrow temperature range of 180-200 °C, CuO was reduced to metallic Cu via the intermediate Cu2O. The Fourier transform magnitude of K-edge Zr of 80 wt.% CuO/ZrO2 showed that the configuration of zirconium in the catalysts was very similar to that of monoclinic zirconia. The Debye rings of 80 wt.% CuO/ZrO2 and 80 wt.% CuO/CeO2 catalysts showed that zirconia was less coagulated at 300 °C than CeO2; heat resistance of ZrO2 is higher than that of CeO2. BET surface area of 80 wt.% CuO/ZrO2 was 85.3 m2/g, and that of 80 wt.% CuO/CeO2 was 46.0 m2/g, suggesting that ZrO2 in the catalyst has micro crystallites and is highly dispersed.