The deactivation mechanism of toluene on MnOx-CeO2 SCR catalyst

Abstract

The simultaneous control of toluene and NOx was investigated on a series of MnOx-CeO2 catalysts, in which NOx was removed in selective catalytic reduction with NH3 into N2, and toluene was removed in catalytic combustion into CO2. We identified the deactivation effect of the MnOx-CeO2 SCR catalyst in the presence of toluene. The NO conversion and N2 selectivity significantly decrease by 50 ppm toluene in the NH3-SCR feed gas. The competitive adsorption of toluene and the deposition of by-products on catalyst surface lead to a considerable decrease in NH3 adsorption. The formation of active Lewis acid sites are dramatically restrained. Meanwhile, the toluene adsorption promotes the formation of oxygen vacancies, increasing the unfavored oxidation reactions of NH3 (non-selective catalytic reduction, NSCR etc.) instead of standard SCR reaction, leading to a significantly decrease in the N2 selectivity. Toluene inhibits the low-temperature SCR activity over MnOx-CeO2 catalysts mainly through the Eley-Rideal mechanism.