Recent advances in catalytic automotive emission control: Passive NO storage at low temperatures

Abstract

AbstractIn the practical applications, a high portion of the NOx is emitted without purification in the cold start period of engine because the selective catalytic reduction (SCR) or NOx storage and reduction (NSR) catalysts are not warmed up. Passive NOx absorbers (PNA) were proposed earlier to store the NOx at low temperatures and release the stored NOx during warm‐up period when the SCR and NSR catalysts downstream are functional, while this concept just attracted great interests recently to meet the extra stringent requirement of governmental emissions regulations. A plant of PNA catalysts, showing different NO adsorption/release characteristics, was disclosed. This review summarizes the recent progress in the development of PNA catalysts. The characteristics of NO adsorption/release on precious metal (i.e., Pt, Pd) loading Al2O3 support catalysts, CeO2 support catalysts, and zeolite support catalysts are summarized and compared.