Selective catalytic reduction of nitrogen monoxide (NO) over a catalyst of mechanically mixed Nb/TiO2 and Mn2O3 (Mn2O3+Nb/TiO2) in an oxidizing atmosphere with propene (C3H6) was studied. The Mn2O3+Nb/TiO2 catalyst showed high activity for the reduction of NO to N-2. The maximum conversion of NO to N-2 was observed at 200-300 degrees C, with about 80% reduction of NO to N-2. Mn2O3 enhanced the formation of NO2 from NO and the activation of propene to react with NO2 for reduction to N-2.