Effects of regeneration conditions on sulfated CuSSZ-13 catalyst for NH3-SCR

To understand the role of regeneration conditions on sulfur-poisoned Cu/SSZ-13 catalysts for NH3-SCR, the physicochemical characterizations and NO2 conversions were investigated. The sulfur-poisoned Cu/SSZ-13 catalysts were treated at different conditions as a function of temperature and duration. TGA results revealed that regeneration at 500 °C only removed parts of sulfur spices and at 700 °C can completely remove all sulfur spices. The physical structural characterizations results illustrate that regeneration below 700 °C has no significant impact on CHA structure for Cu/SSZ-13 catalysts, while dealumination occurs on poisoned Cu/SSZ-13 when regeneration temperature is higher than 700 °C. EPR and H2-TPR results show that the sulfate decomposition and Cu migration reactions involved during regeneration and, as a result, the content of Cu2+ gradually increased as the extent of regeneration increased. The kinetics tests support that NOx conversion recovery is related to the content of Cu2+ increase during regeneration. Our study reveals that the optimum regeneration temperature is 700 °C, because severe dealumination at 750 °C inhibited Cu2+ amount increase.