Abstract: A series of CuZnAl catalysts for methanol steam reforming have been prepared via pyrogenation of hydrotalcite-like precursors at 600 ℃, which were synthesized by the traditional Na2CO3/NaOH coprecipitation method using nitrates, acetates, sulfates, and chlorides of copper and zinc as Cu(Ⅱ) and Zn(Ⅱ) sources. The use of acetates and nitrates facilitated the crystallization of CuZnAl hydrotalcites, and the derived catalysts had large specific surface area, high Cu dispersion, and good reducibility of CuO. The use of sulfates and chlorides inhibited hydrotalcite crystallization, leading to the reduction of the specific surface area and the reducibility of CuO in the corresponding catalysts. The catalysts prepared from acetates and nitrates were highly active and stable for methanol steam reforming, but those prepared from sulfates and chlorides were inactive due to the poisoning of SO2-4 and Cl- residues. The catalyst prepared from acetates provided much lower CO concentration (0.03%-0.04%) in the dry product gas compared to the catalyst prepared from nitrates (0.2%) with >95% methanol conversion at 250 ℃ and WHSV of 3.28 h-1. Furthermore, CO concentration was reduced to 0.005% over the catalyst prepared from acetates with >95% methanol conversion when the reaction temperature was decreased to 210 ℃ and WHSV to 0.5 h-1. N2O titration and CO2 temperature-programmed desorption measurements indicated that both of the catalysts from acetates and nitrates possessed close values (～50 m2/g) of Cu surface area and very similar basic properties. Temperature-programmed reduction results showed that the peak temperature of CuO for the catalyst from acetates was 70 ℃ lower than that for the catalyst from nitrates, which was attributed to the strong interaction between CuO and ZnO. It might be the intrinsic reason for the significant reduction of the CO concentration on the catalyst from acetates.

Key words: copper oxide, zinc oxide, alumina, hydrotalcite, methanol, hydrogen, steam reforming, fuel cell