Novel Effect of H2O on the Low Temperature Selective Catalytic Reduction of NO with NH3 over MnOx—CeO2: Mechanism and Kinetic Study

Abstract

H2O generally shows a strong inhibition on the low temperature selective catalytic reduction (SCR) reaction. However, a novel phenomenon was discovered that the low temperature SCR reaction over MnOx—CeO2 was promoted by H2O. The rate constants of N2 and N2O formation over MnOx—CeO2 were calculated using the steady-state kinetic study. It showed that both the rate constants of N2 and N2O formation decreased in the presence of H2O, and the promotion of the SCR reaction over MnOx—CeO2 by H2O was mainly attributed to the inhibition of N2O formation. Meanwhile, the influence of H2O on the elementary reaction of N2O formation over MnOx—CeO2 was studied using the transient reaction study. It indicated that the inhibition of N2O formation over MnOx—CeO2 by H2O was not only attributed to the competition adsorption of H2O with NH3 but also related to the decrease of the oxidation ability of MnOx—CeO2 in the presence of H2O.