OXIDATION CATALYSTS FOR ENGINES PRODUCING LOW TEMPERATURE EXHAUST STREAMS
First Claim
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1. 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 (CO2) and at least a portion of the HC to CO2 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 (CeZrCuO2) and (ii) a discrete PGM layer consisting essentially of particles of at least one platinum group metal dispersed on particles of aluminum oxide (PGM/Al2O3), 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/Al2O3.
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Abstract
The oxidation of carbon monoxide (CO) and hydrocarbons (HC) in an oxygen-containing gas stream, such as the exhaust stream from a diesel engine, or other lean-burn engine, may be catalyzed using a combination of mixed oxide particles of cerium, zirconium and copper, and discrete particles of an alumina-supported platinum group metal catalyst. The catalyzed oxidation of CO and HC by this combination of oxidation catalyst particles is effective at temperatures below 300° C.
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Citations
12 Claims
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1. 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 (CO2) and at least a portion of the HC to CO2 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 (CeZrCuO2) and (ii) a discrete PGM layer consisting essentially of particles of at least one platinum group metal dispersed on particles of aluminum oxide (PGM/Al2O3), 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/Al2O3. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- the method comprising;
Specification