Reduction of nitrogen oxide by carbon monoxide over pure and platinum-doped LaMnO3 perovskites. Effect of oxygen on the reaction

Abstract

The reduction of NO by CO has been studied using pure and platinum-doped LaMnO3 perovskites as catalysts. The reaction products always include nitrogen monoxide, whose amount varies with temperature. The reaction kinetics for the two catalysts are different and have been described by different rate laws. Considerable differences have also been found in the apparent activation energies: in the presence of Pt it is about half that for the reaction catalyzed by pure LaMnO3. Both the catalysts exhibit good catalytic properties, but the platinum-doped LaMnO3 shows a higher catalytic activity. The presence of oxygen in the inlet mixture affects considerably the kinetics of the reaction catalyzed by platinum-doped LaMnO3. The conversion of NO passes through a maximum at an oxygen/carbon monoxide molar ratio, m, of 1.8. At m > 1.8, CO is oxidized preferentially by oxygen rather than by NO.