Patent ID: 7576031

Claim:
A diesel oxidation catalyst for abatement of exhaust gas emissions from a diesel engine containing hydrocarbons and carbon monoxide comprising: (a) a carrier substrate; (b) a bottom washcoat layer coated on said carrier substrate comprising a high-surface area support material and a precious metal catalyst containing 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; (c) 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 containing platinum (Pt) and palladium (Pd) in a Pt:Pd weight ratio; and (d) 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, and wherein the oxidation catalyst oxidizes the carbon monoxide and hydrocarbons to carbon dioxide and water.