Insight into the SO2 resistance mechanism on γ-Fe2O3 catalyst in NH3-SCR reaction: A collaborated experimental and DFT study

SO2 poisoning of NH3-SCR catalysts at low temperature (< 300 degrees C) is still an austere challenge. In this work, gamma-Fe2O3 was taken as a model catalyst and the effect of reaction temperature on the catalytic activity in the presence of SO2 were fully revealed. SO2 introduction has no negative effect on the activity at 300 degrees C, which gradually improves with the extension of time. While for 225-275 degrees C, the activity decreases firstly and then increases slowly. The formatted sulfate species inhibits the adsorption of NOx, cuts off L-H reaction pathway and leads to the initial decline. While the deposited ammonium bisulfate (ABS) can be consumed continuously by NO + O-2, implying the formation and consumption of ABS have reached a dynamic equilibrium. Moreover, the formation of ferric sulfate species results in the enhancement of surface acidity, which leads to the promotion of the E-R reaction pathway and further facilitates the increase of activity.