NO{sub}x storage-reduction catalyst (NSR Catalyst) for automotive engines

摘要

NO{sub}x storage-reduction catalysts (NSR catalysts) have developed for lean-burn and gasoline direct injection engines. One of the main causes of deterioration of NSR catalysts is sulfur poisoning. SO{sub}2 is oxidized on the precious metal andreacts with the NO{sub}x storage compounds to form sulfates. The decomposition of formed sulfates is essential to improve the durability of the catalyst. The composition of NO{sub}x storage components and acidity of supports are optimized to minimize thegrowth of the size of sulfate particles. The enhancement of the dispersion of the precious metal also affects sulfate decomposition. Even in the present time, sulfur tree fuel is necessary for NSR catalyst to keep its high performance during long timebecause the NO{sub}x conversion performance of developed NSR catalyst decreases with increasing sulfur content in fuel.