Surface properties and reactivity of Cu/γ-Al2O3 catalysts for NO reduction by C3H6: Influences of calcination temperatures and additives Original Research Article

The influences of calcination temperatures and additives for 10 wt.% Cu/γ-Al2O3 catalysts on the surface properties and reactivity for NO reduction by C3H6 in the presence of excess oxygen were investigated. The results of XRD and XPS show that the 10 wt.% Cu/γ-Al2O3 catalysts calcined below 973 K possess highly dispersed surface and bulk CuO phases. The 10 wt.% Cu/γ-Al2O3 and 10 wt.% Mn–10 wt.% Cu/γ-Al2O3 catalysts calcined at 1073 K possess a CuAl2O4 phase with a spinel-type structure. In addition, the 10 wt.% La–10 wt.% Cu/γ-Al2O3 catalyst calcined at 1073 K possesses a bulk CuO phase. The result of NO reduction by C3H6 shows that the CuAl2O4 is a more active phase than the highly dispersed and bulk CuO phase. However, the 10 wt.% Mn–10 wt.% Cu/γ-Al2O3 catalyst calcined at 1073 K possesses significantly lower reactivity for NO reduction than the 10 wt.% Cu/γ-Al2O3 catalyst calcined at 1073 K, although these catalysts possess the same CuAl2O4 phase. The low reactivity for NO reduction for 10 wt.% Mn–10 wt.% Cu/γ-Al2O3 catalyst calcined at 1073 K is attributed to the formation of less active CuAl2O4 phase with high aggregation and preferential promotion of C3H6 combustion to COx by MnO2. The engine dynamometer test for NO reduction shows that the C3H6 is a more effective reducing agent for NO reduction than the C2H5OH. The maximum reactivity for NO reduction by C3H6 is reached when the NO/C3H6 ratio is one.