Mechanism of SO2 effect on the simultaneous removal of NOx and propane over bifunctional NiMn2O4-CeO2 catalysts.

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) are the main pollutants in flue gas, and the synergistic removal of NOx and VOCs in the presence of SO2 is still a challenge. In this work, the microstructure of NiMn2O4-CeO2 catalysts and the distribution of sulfur-containing substances were studied to reveal the inactivation mechanism of sulfur poisoning. NOx conversion could reach more than 80 % at 100-250 °C, and C3H8 conversion could achieve 90 % at 210 °C in the synergistic reaction on NiMn2O4-CeO2 catalyst, which has dual active sites with propane oxidation and SCR reactions carried out at Mn and Ni sites, respectively. In addition, the intrinsic effect of SO2 on propane oxidation and NOx reduction were investigated by decoupling. For propane oxidation, mechanistic studies have shown that manganese sulfate generated by SO2 hindered further reactions by inhibiting the breaking of the CC bond. For denitration reaction, the generation of sulfate not only resulted in electron transfer from Ni to Mn thereby reducing reaction activity, but also blocked the L-H pathway by inhibiting NO adsorption. This work provides guidelines and strategies to mitigate SO2 poisoning in the simultaneous removal of NOx and light alkane.