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

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