Influence of La2O3 and ZrO2 as promoters on surface and catalytic properties of CuO/MgO system prepared by sol-gel method

The physicochemical, surface and catalytic properties of pure and doped CuO/MgO solids with La2O3 and ZrO2 prepared by sol-gel method followed by calcination at 350, 500 and 650 degrees C were investigated. The dopant concentrations of La2O3 and ZrO2 were 2.0, 4.0, 6.0 and 8.0 mol%. The amounts of CuO loaded were 0.1, 0.2 and 0.3 mol. The techniques employed were XRD, FTIR, nitrogen adsorption at -196 degrees C, CO oxidation by O-2 at 225-275 degrees C and H2O2 decomposition in aqueous solution at 30-50 degrees C. The results obtained revealed that the doping of CuO/MgO solids with different amounts of La2O3 and ZrO2 brought about a progressive decrease in the degree of crystallinity of CuO and MgO phases and their particle size. The doping of CuO/MgO solid catalysts with La2O3 led to a progressive decrease in their specific surface areas, while the doping with ZrO2 exerted opposite effect. The doping process with La2O3 and ZrO2 brought about a progressive increase in the catalytic activities of the investigated solid catalysts towards CO oxidation by O-2 to an extent proportional to the amount of dopant added. The doping of solid catalysts with La2O3 led to a decrease in their catalytic activities towards H2O2 decomposition, while the doping with ZrO2 led to an increase in the catalytic activity of the investigated solids calcined at different temperatures. The increase in the copper content of loading led to a decrease in the specific surface areas of solid catalysts, while for catalysis the increase of copper content resulted in a progressive increase in their catalytic activities towards CO oxidation for solids calcined at different temperatures and towards H2O2 for solids calcined at 350 and 500 degrees C. The doping process led to an increase in the concentration of catalytically active constituents on the catalyst surface taking part in the catalytic process. (c) 2005 Elsevier B.V. All rights reserved.