Water tolerance of DeNOx SCR catalysts using hydrocarbons:: Findings, improvements and challenges

The recent developments on the effect of H2O on deNO(x) performance of a variety of SCR catalysts selectively removing NOx by hydrocarbons in excess oxygen have been reviewed. In particular, the water tolerance of the catalyst is summarized to illustrate a common deactivation behavior of SCR catalyst for the reduction of NO by hydrocarbons under wet feed gas mixture. Earlier proposals elucidating the possible cause of the catalyst deactivation under wet conditions are discussed, focusing mainly on the catalyst characteristics. A promising way, which can improve the water tolerance and the hydrothermal stability of zeolite-based SCR catalyst, is also described.