A comparative study of Ag/Al2O3 and Cu/Al2O3 catalysts for the selective catalytic reduction of NO by C3H6

The selective catalytic reduction (SCR) of NO by C3H6 in excess oxygen was evaluated and compared over Ag/Al2O3 and Cu/Al2O3 catalysts. Ag/Al2O3 showed a high activity for NO reduction. However, Cu/Al2O3 showed a high activity for C3H6 oxidation. The partial oxidation of C3H6 gave surface enolic species and acetate species on the Ag/Al2O3, but only an acetate species was clearly observed on the Cu/Al2O3. The enolic species is a more active intermediate towards NO + O2 to yield—NCO species than the acetate species on the Ag/Al2O3 catalyst. The Ag and Cu metal loadings and phase changes on Al2O3 support can affect the activity and selectivity of Ag/Al2O3 and Cu/Al2O3 catalysts, but the formation of enolic species is the main reason why the activity of the Ag/Al2O3 catalyst for NO reduction is higher than that of the Cu/Al2O3 catalyst.