Reaction Mechanism of NO Reduction by CH4over Rare Earth Oxides in Oxidizing Atmosphere

Abstract

Abstract Rare earth oxides have been examined as catalysts for the catalytic reduction of NO by CH4 in the presence of oxygen. Among the rare earth oxides examined, Sc2O3 and Sm2O3 were found to be active for this reaction. For the Sm2O3 catalyst, ZrO2 was the most effective support. The mechanism of the reaction was studied over the Sm2O3/ZrO2. Kinetic studies indicated that CH4 oxidation is initiated by O2, and NO can react only with CH3 radicals formed from the reaction of CH4 with O2. Ab-initio MO calculations also suggested that CH3 radical is a more favorable reducing species for selective reduction of NO than CH4. It is thus proposed that NO is reduced into N2 by the CH3 radical formed from the activation of methane by oxygen.