The structure of CuO-ZrO2 mixed oxides and its influence on the catalytic selective reduction of NO by propene

Different catalytic performances of CuO - ZrO2 mixed oxides prepared by imp regnation or co precipitation method for selective reduction of NO tin the presence of O-2 were investigated. The structures and properties of the cat alysts were characterized Ly XRD, BET surface area measurement, EXAFS and H -2 - TPR measurements. The CuO - ZrO2 mixed oxides prepared by impregnation method had larger surface area than those prepared by co - precipitation m ethod. The zirconium oxide was stabilized at the tetragonal phase. EXAFS me asurement shows that in the CuO - ZrO2 mixed oxides prepared by impregnatio n method the copper ions first fill in the surface hole of zirconium oxide and stay there as Cu+. Under the calcination at 500 degreesC, the Cu2+. ion s that brought into ZrO2 by co- precipitation method carl replace Zr4+ and form a uniform amorphous solid solution, Tile high -dispersion of Cu ions i n zirconium oxide was the key element that led to formation of highly dispe rsed isolated copper species on the surface. Substitution of Zr4+ by Cu2+ i ons could decrease the reducibility of copper species and the activity of t he complete oxidation of propene. The local structure difference of copper species was the main reason for the high activity and selectivity of the Cu O - ZrO2 mixed oxides prepared by co - precipitation method.