Recent advances in zeolites for the selective catalytic reduction of NO x with NH 3

Medium- and large-pore zeolite catalysts (e.g. ZSM-5, Beta) have long been used for the selective catalytic reduction of NOx with NH3 (NH3-SCR) reaction. But their hydrothermal stability and poisoning resistance are poor, so they still fall short of the ideal standards for industrial applications. Cu-based small-pore zeolite catalysts have attracted extensive attention for application on diesel vehicles due to their excellent activity, high hydrothermal stability, and good poisoning resistance in the NH3-SCR of NOx. To better understand the application prospects of these small-pore zeolite catalysts in the purification of diesel vehicle exhaust, their structures are introduced first in this paper. Then, the applications of small-pore zeolite catalysts in NH3-SCR and related factors affecting activity, including the influence of their structure-activity relationship, Si/Al ratio, synthetic method, and post-treatment, are introduced. Moreover, the reaction mechanism and deactivation (hydrothermal deactivation, sulfur poisoning, hydrocarbon poisoning, and chemical poisoning) of small-pore zeolite catalysts in NH3-SCR are reviewed. Finally, the opportunities and challenges of applying small-pore zeolite catalysts in NH3-SCR are summarized, so as to facilitate the development of novel small-pore zeolite catalysts for NH3-SCR with high performance and stability in the future.