Knowledge and know-how in improving the sulfur tolerance of deNO x catalysts

Abstract

Catalytic removal of NO x under lean-burn conditions is challenging to attain the future stringent NO x emission standards. Selective catalytic reduction (SCR) of NO x with different reducing agents and NO x storage-reduction (NSR) are viewed as the two most promising technologies for NO x removal. Although a variety of catalytic systems have been developed for these processes, their practical applications remain difficult due to catalyst deactivation caused by SO 2 in the exhaust gases. Therefore, improving catalyst tolerance against SO 2 is one of the most important targets in the deNO x catalyst development. This review focuses on the knowledge and know-how that have been developed in improving the sulfur tolerance of deNO x catalysts. Ag/Al 2O 3 is the most promising catalyst for the HC-SCR of NO x . Support modification, H 2 co-feeding and some other strategies to improve the sulfur tolerance of Ag/Al 2O 3 are discussed. Some novel catalyst systems with high sulfur tolerance for NH 3-SCR, H 2-SCR and NSR are addressed, respectively. For NSR catalysts, developing novel sulfur resistant NO x storage systems and effective desulfation processes seem to be two avenues to improve their sulfur resistance.