Hydrothermal Aging Alleviates the Phosphorus Poisoning of Cu-SSZ-39 Catalysts for NH 3 -SCR Reaction.

As a new type of catalyst with the potential for commercial application in NO x removal from diesel engine exhausts, Cu-SSZ-39 catalysts must have excellent resistance to complex and harsh conditions. In this paper, the effects of phosphorus on Cu-SSZ-39 catalysts before and after hydrothermal aging treatment were investigated. Compared with fresh Cu-SSZ-39 catalysts, phosphorus poisoning significantly decreased the low-temperature NH 3 -SCR catalytic activity. However, such activity loss was alleviated by further hydrothermal aging treatment. To reveal the reason for this interesting result, a variety of characterization techniques including NMR, H 2 -TPR, X-ray photoelectron spectroscopy, NH 3 -TPD, and in situ DRIFTS measurements were employed. It was found that Cu-P species produced by phosphorus poisoning decreased the redox ability of active copper species, resulting in the observed low-temperature deactivation. After hydrothermal aging treatment, however, Cu-P species partly decomposed with the formation of active CuO x species and a release of active copper species. As a result, the low-temperature NH 3 -SCR catalytic activity of Cu-SSZ-39 catalysts was recovered.