Preparation of CuO/ZnO/Al2O3 catalysts for methanol synthesis using parallel-slurry-mixing method

A series of CuO/ZnO/γ-Al2O3 catalysts with different Al2O3 contents were prepared using the parallel-slurry-mixing method, in which an aqueous solution of Cu2+ and Zn2+ mixed nitrates and an aqueous solution of Na2CO3 were poured into a precipitation vessel containing γ-Al2O3 slurry in a parallel-flow manner. The catalyst structure and its performance for methanol synthesis were investigated. The results indicated that Al2O3 as a structural promoter can inhibit CuO and ZnO crystallites from enlarging during calcination. The catalyst with a Cu/Zn/Al ratio of 4/5/1 (molar ratio) exhibits the highest catalytic activity. With an increase in Al content, the amount of (Cu0.3Zn0.7)5(CO3)2(OH)6 phase in the catalyst precursor before calcination decreases, whereas that of Cu2CO3(OH)2 phase increases; (Cu0.3Zn0.7)5(CO3)2(OH)6 in the precursor is beneficial to the catalytic activity of the final Cu/ZnO/γ-Al2O3 catalyst.