Review of Core-shell structure zeolite-based catalysts for NO emission control.

Nitrogen oxides (NO) from diesel engine exhaust, is one of the major sources of environmental pollution. Currently, selective catalytic reduction with ammonia (NH-SCR) is considered to be the most effective protocol for reducing NO emissions. Nowadays, zeolite-based NH-SCR catalysts have been industrialized and widespread used in this field. Nevertheless, with the increasingly stringent environmental regulations and implementation of the requirement of "zero emission" of diesel engine exhaust, it is extremely urgent to prepare catalysts with superior NH-SCR activity and exceptional resistance to poisons (SO, alkali metals, hydrocarbons, etc.). Core-shell structure zeolite-based catalysts (CSCs) have shown great promise in NH-SCR of NO in recent years by virtue of its relatively higher low-temperature activity, broader operation temperature window and outstanding resistance to poisons. This review mainly focuses on the recent progress of CSCs for NH-SCR of NO with three extensively investigated SSZ-13, ZSM-5, Beta zeolites as cores. The reaction mechanisms of resistance to sulfur poisoning, alkali metal poisoning, hydrocarbon poisoning, and hydrothermal aging are summarized. Moreover, the important role of interfacial effect between core and shell in the reaction of NH-SCR was clarified. Finally, the future development and application outlook of CSCs are prospected.