Patent ID: 7875573
Filing Date: 2011-01-25
Classification: B01J,F01N,Y02T

Abstract:
1. An emission treatment system for treating exhaust gas emissions from a diesel engine containing hydrocarbons, carbon monoxide, and particulate matter comprising: a diesel oxidation catalyst comprising a carrier substrate comprising a bottom washcoat layer coated on said carrier substrate comprising a high-surface area support material and a precious metal catalyst consisting of platinum (Pt) and palladium (Pd) in a Pt:Pd weight ratio, wherein said support is a substantially silica-free high-surface area support material, and wherein said bottom washcoat layer does not contain a hydrocarbon storage component; a top washcoat layer coated over said bottom washcoat layer comprising a high-surface area support material, one or more hydrocarbon storage components, and a precious metal catalyst consisting of platinum (Pt) and palladium (Pd) in a Pt:Pd weight ratio; and wherein said Pt:Pd weight ratio in said top washcoat layer is from about 2:1 to up to about 4:1 and is greater than said Pt:Pd weight ratio of said bottom washcoat layer; a soot filter located downstream from the diesel oxidation catalyst to trap particulate matter from the exhaust gas; and a catalyst for the conversion of NOx located downstream from the soot filter.