Synergistic effect and mechanism of FeOx and CeOx co-doping on the superior catalytic performance and SO2 tolerance of Mn-Fe-Ce/ACN catalyst in low-temperature NH3-SCR of NOx

Abstract

Developing alternative NH3-SCR catalysts with high SO2 tolerance is of great significance for NOx emission control at low temperature. For further improving the catalytic performance and SO2 tolerance of nitric acid modified activated carbon (ACN) loaded MnOx catalyst (Mn/ACN), FeOx and CeOx were co-doped by impregnation. FeOx and CeOx co-doped Mn-Fe(0.4)-Ce(0.4)/ACN exhibited improved catalytic activity, N2 selectivity, and SO2 tolerance. The NOx conversion of Mn-Fe(0.4)-Ce(0.4)/ACN was higher than 95% in 100–250 °C and remained around 91% after 32 h reaction under 100 ppm SO2 and 10 vol% H2O at 175 °C. Co-doping FeOx and CeOx greatly enhanced the surface acidity, redox properties, and surface chemisorbed oxygen of Mn-Fe(0.4)-Ce(0.4)/ACN through the interaction among Mnn+, Fen+, and Cen+, resulting in significantly promoted NH3-SCR performance. The stronger surface acidity and promoted catalytic activity effectively inhibited the adsorption of SO2 and the reaction between SO2 and adsorbed NH3, respectively. Meanwhile, the adsorbed SO2 was preferentially induced to react with CeOx, preventing MnOx and FeOx from being sulfated. Finally, the synergistic mechanism of FeOx and CeOx co-doping on better SO2 tolerance for Mn-Fe(0.4)-Ce(0.4)/ACN catalyst was proposed.