The influence of SO2 presence during high temperature hydrothermal aging (600, 700, and 800 °C) on the performance of Cu-SSZ-13 prepared by the conventional ion-exchange method for selective catalytic reduction of NOx by NH3 (NH3-SCR) was studied. The high-temperature activity of Cu-SSZ-13 is obviously enhanced by the SO2 presence for the 700 and 800 °C-aged samples and is not hampered for the 600 °C-aged sample. The presence of SO2 during hydrothermal aging has no influence on the framework Al. The interaction of Cu2+ with SO2 results in the formation of ZCuHSO4, which helps suppress the aggregation of Cu2+ into CuO and maintain more isolated Cu2+, leading to higher activity at high temperatures. The low Cu content yields higher relative population of Cu2+ species at more stable sites. The low-temperature (≤350 °C) activity is slightly lowered for the 600 and 700 °C-aged samples.
- Hydrothermal aging