Effects of Preparation Conditions on Surface and Catalytic Properties of Copper and Zinc Mixed Oxides System

Copper-zinc mixed oxides treated with small amounts of alumina and having the formula 0.5 CuO: 0.5ZnO: 0.05 Al2O3 were prepared by coprecipitation of their mixed hydroxides from their mixed nitrates solutions using 1 M NaOH solution. The precipitation was carried out at different pH values varying between 7 to 9.5 and at 50 and 70 o C. The results revealed that the bulk of various solids consisted of CuO and ZnO having ratios varying between 0.91 and 1.20. While the surface Cu/Zn ratio was bigger than those present in the bulk and varied between 1.16 to 1.64 depending on the pH value and calcination temperature. The mixed oxide solids existed as nanocrystalline CuO and ZnO phases. The surface characteristics are strongly dependent on both the pH value and calcination temperature. The computed SBET val- ues varied between 21and 108 m 2 /g and all adsorbents are mesoporous solids. The prepared solids showed a good cata- lytic activity in CO oxidation by O2 which proceeds via first order kinetics in all cases. The activation energy of the cata- lyzed reaction was determined for various solids and the computed values were very small indicating the big catalytic ac- tivity of the investigated solids.