Insights into SO 2 Poisoning Mechanisms of Fresh and Hydrothermally Aged Cu-KFI Catalysts for NH 3 -SCR Reaction.

The complex poisoning of Cu-KFI catalysts by SO 2 and hydrothermal aging (HTA) was investigated. The low-temperature activity of Cu-KFI catalysts was restrained by the formation of H 2 SO 4 and then CuSO 4 after sulfur poisoning. Hydrothermally aged Cu-KFI exhibited better SO 2 resistance than fresh Cu-KFI since HTA significantly reduced the number of Brønsted acid sites, which were considered to be the H 2 SO 4 storage sites. The high-temperature activity of SO 2 -poisoned Cu-KFI was basically unchanged compared to the fresh catalyst. However, SO 2 poisoning promoted the high-temperature activity of hydrothermally aged Cu-KFI since it triggered CuOx into CuSO 4 species, which was considered as an important role in the NH 3 -SCR reaction at high temperatures. In addition, hydrothermally aged Cu-KFI catalysts were more easily regenerated after SO 2 poisoning than fresh Cu-KFI on account of the instability of CuSO 4 .