Patent ID: 8479493

Claim:
A method of oxidizing carbon monoxide (CO) and hydrocarbons (HC) in an exhaust gas stream of an internal combustion engine; the method comprising: operating an internal combustion engine to burn a mixture of air and fuel in which a fuel content in the mixture is lean with respect to the stoichiometric air-to-fuel mass ratio, the engine producing an exhaust gas stream having a temperature that is often below 300 degrees Celsius; passing the exhaust gas stream in contact with an oxidation catalyst for a period of time sufficient to oxidize substantially all of the CO to carbon dioxide (CO 2 ) and at least a portion of the HC to CO 2 and water; the oxidation catalyst being dispersed on channel walls of a flow-through support body as a washcoat comprising (i) a mixed oxide layer consisting essentially of particles of co-precipitated mixed oxides of cerium, zirconium, and copper (CeZrCuO 2 ) and (ii) a discrete PGM layer consisting essentially of particles of at least one platinum group metal dispersed on particles of aluminum oxide (PGM/Al 2 O 3 ), the layers of the washcoat being arranged such that a portion of the CO present in the exhaust gas stream is oxidized before the exhaust gas stream contacts the particles of PGM/Al 2 O 3 .