Exhaust system with a modified lean NOx trap

文件类型：PDF文档
文件大小：278K
A modified lean nitrogen oxides (NOx) trap (LNT), adsorbs or stores (NOx) at temperatures below about 200 degrees C and desorbs or releases the NOx at temperatures above about 200 degrees C. A first layer of the modified LNT comprises a NOx adsorbent component and one or more platinum group metals. A second layer comprises a diesel oxidation catalyst zone and a nitrogen oxide (NO) oxidation zone. The diesel oxidation catalyst zone comprises a platinum group metal and a zeolite. The NO oxidation zone comprises a platinum group metal and a carrier. The NOx adsorbent component may comprise an alkaline earth metal, alkali metal or rare earth metal supported on an inorganic oxide such as magnesia-alumina, or barium. The carrier of the NO oxidation zone may comprise alumina, ceria and manganese. The lean Nox trap may be used to treat exhaust gas from an internal combustion engine in combination with a urea injection system and an ammonia-selective catalytic reduction catalyst (SCR). The SCR may comprise vanadia-titania and a zeolite with iron or copper.