Hydrogen Production by Steam Reforming of Methanol

Abstract

Steam reforming of methanol, CH 3 OH + H 2 O → 3H 2 + CO 2 , was carried out over Cu/ZnO and various supported group 8-10 metal catalysts. Over Cu/ZnO catalysts prepared by a coprecipitation method, the steam reforming of methanol occurs with high selectivity regardless of composition of the catalyst and structure of the precursor (aurichalcite, malachite, hydrozincite or their mixture). The Cu/ZnO catalysts prepared from the aurichalcite precursor are more active than those prepared from other precursors. By contrast, over supported group 8-10 metal catalysts, such as supported Pd, Pt, Co, Ni, Rh, Ir and Ru catalysts, hydrogen and carbon monoxide are predominantly produced by decomposition of methanol, CH 3 OH → 2H 2 + CO. The selectivity for the steam reforming is lower than those over Cu/ZnO catalysts. However, the selectivity for the steam reforming is markedly improved upon the previous reduction of Pd/ZnO, Pd/Ga 2 O 3 , and Pd/In 2 O 3 at higher temperatures. Upon addition of Zn to the supported Pd catalysts, the selectivity for the steam reforming and the rate of hydrogen formation are markedly increased. Over Zn modified Pd/CeO 2 catalyst, the selectivity attains to 99.0%, being comparable to Cu/ZnO catalysts. Combined results with temperature programmed reduction, XRD, XPS and AES measurements revealed that PdZn alloy was formed by the previous reduction of Pd/ZnO or Zn modified pd/CeO 2 catalyst. Catalytic functions of Pd are greatly modified upon the formation of PdZn alloys.