CuO/ZnO catalysts for methanol steam reforming: The role of the support polarity ratio and surface area

Abstract

The effect of surface area and polarity ratio of ZnO support on the catalytic properties of CuO/ZnO catalyst for methanol steam reforming (MSR) are studied. The surface area of ZnO was varied changing the calcination temperature and its polarity ratio was modified using different Zn precursors, zinc acetate and zinc nitrate. It was found that the copper dispersion and copper surface area increase with the surface area of the ZnO support and the polarity ratio of ZnO strongly influences the reducibility of copper species. A higher polarity ratio promotes the reducibility, which is attributed to a strong interaction between copper and the more polar ZnO support. Interestingly, it was observed that the selectivity of CuO/ZnO catalysts (lower CO yield) increases with the polarity ratio of ZnO carriers. As another key result, CuO/ZnOAc375 catalyst has proven to be more selective (up to 90 %) than a reference CuO/ZnO/Al2O3 sample (G66-MR, Süd Chemie). The activity of the best performing catalyst, CuO/ZnOAc375, was assessed in a Pd-composite membrane reactor and in a conventional packed-bed reactor. A hydrogen recovery of ca. 75 % and a hydrogen permeate purity of more than 90 % was obtained. The Pd-based membrane reactor allowed to improve the methanol conversion, by partially supressing the methanol steam reforming backward reaction, besides upgrading the reformate hydrogen purity for use in HTPEMFC.