Eley−Rideal path enhanced NH3-SCR: Central Fe atoms activation for electron transfer promotion

Abstract

Manganese modified Fe2O3 catalyst is a promising candidate to replace the commercial NH3-SCR catalyst for controlling NOx emission due to its superior performance and N2 selectivity at low temperature. In order to elucidate the effects of different modification methods of Mn on physicochemical properties and reaction mechanism in Fe-Mn binary catalysts, two kinds of Mn modified Fe2O3 are prepared by co-precipitation and impregnation method, respectively. Compared with MnO2 loaded Fe2O3, Mn doped Fe2O3 achieves above 85 % of NOx conversion with 20 % increase in N2 selectivity within 100–200°C. Transient reaction experiments and DFT calculation results prove that doping Mn effectively increases the reaction rate of the main reaction and reduces the formation of N2O through Eley−Rideal path. The formation of multiple Fe-O-Mn structures after Mn doping facilities the formation of coordination bond between the central Fe atoms and NH3 via modulating local charge density of Fe atoms, effectively improving the adsorption of NH3 and preventing its excessive oxidation, which leads to high activity and N2 selectivity at low temperature. This mechanism provides theoretical support for increasing the activity and N2 selectivity of NH3-SCR catalysts at low temperature and gains clear insight on the interaction between binary metal oxides.