Selective catalytic reduction catalyst system

摘要

Described are SCR catalyst systems comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition having a faster DeNOx response time when exposed to ammonia than the second catalyst composition and the second SCR catalyst composition has a higher steady state DeNOx performance than the first catalyst composition. The SCR catalyst systems are useful in methods and systems to catalyze the reduction of nitrogen oxides in the presence of a reductant.

主权项

1. A selective catalytic reduction (SCR) catalyst hybrid system for removing NOx from engine exhaust, the system comprising a first SCR catalyst composition and a second SCR catalyst composition arranged in the system, the first SCR catalyst composition having a faster DeNOx response time when exposed to ammonia than the second catalyst composition and the second SCR catalyst composition has a higher steady state DeNOx performance than the first catalyst composition;
wherein the first catalyst composition comprises vanadia/titania stabilized with tungsten; and wherein the second catalyst composition comprises a metal-exchanged zeolite, excluding Cu-exchanged or Fe-exchanged ZSM-5 or Beta zeolites.