2002 Volume 45 Issue 5 Pages 288-294
The catalytic activities of thirteen types of single component metal oxides were measured for the selective catalytic reduction (SCR) of NO with ethene in excess oxygen and related reactions to elucidate the characteristic features of catalyst activity. The related reactions were the oxidation of NO2 with O2, the oxidation of C2H4 with O2, the reduction of NO2 with C2H4 in the absence of O2, and the reduction of NO with C2H4 in the absence of O2. Alumina exhibited the highest activity for SCR, followed by ZrO2, SNO2, MgO, CaO, Y2O3, and TiO2; WO3, Co3O4, CuO, Fe2O3, ZnO, and SiO2 showed little activity. The active catalysts including alumina had the characteristic features of high activities for both the oxidation of NO to NO2 and the reduction of NO2 with C2H4 to form N2, as well as low activity for the oxidation of C2H4 with O2. Although Co3O4, CuO, and Fe2O3 showed high activities for the oxidation of NO to NO2, they were also highly active for the oxidation of C2H4 with O2. Therefore, C2H4 was consumed without reduction of NO over these catalysts. The characteristic features for the active catalysts also support the reaction scheme that the SCR proceeds by the successive reactions of the oxidation of NO to NO2 and the reduction of NO2 with C2H4 to form N2.
