Exhaust system for a lean-burn ic engine comprising a pgm component and a scr catalyst

摘要

An exhaust system 10 for a vehicular lean-burn internal combustion engine comprises: (a) a first substrate monolith 6 comprising a SCR catalyst; (b) at least one second substrate monolith 4 comprising a catalytic washcoat coating comprising at least one platinum group metal (PGM) disposed upstream of the first substrate monolith; and (c) a third substrate monolith 2 disposed between the first substrate monolith and the or each second substrate monolith, wherein at least one PGM on the or each second substrate monolith 4 is liable to volatilise when the or each second substrate monolith 4 is exposed to relatively extreme conditions including relatively high temperatures, and wherein the third substrate monolith 2 comprises a washcoat coating comprising at least one metal oxide for trapping volatilised PGM.