Engine Exhaust Catalysts Containing Palladium-Gold
An engine exhaust catalyst exhibits improved CO oxidation performance relative to conventional engine exhaust catalysts and includes a first supported catalyst comprising platinum and a second supported catalyst comprising palladium and gold species in close contact. The first supported catalyst may be a platinum catalyst, a platinum-palladium catalyst, or a platinum catalyst promoted with bismuth, and the second supported catalyst preferably has a palladium to gold weight ratio of about 0.85:1.0. To improve aged catalyst performance, the first and second supported catalysts are coated onto different layers, zones, or monoliths of the substrate for the engine exhaust catalyst.
1 - 36 . (canceled)
37 . An engine exhaust catalyst comprising a substrate and a coating on the substrate that includes metal nanoparticles consisting essentially of palladium and gold species.
38 . The engine exhaust catalyst according to claim 1 , wherein the coating comprises a supported platinum-based catalyst containing platinum nanoparticles and a supported palladium-gold catalyst containing the metal nanoparticles consisting essentially of palladium and gold species.
39 . The engine exhaust catalyst according to claim 2 , wherein the supported platinum-based catalyst comprises platinum and one or more other metals.
40 . The engine exhaust catalyst according to claim 3 , wherein the supported platinum-based catalyst comprises platinum and palladium.
41 . The engine exhaust catalyst according to claim 3 , wherein the platinum-based catalyst comprises platinum and a promoter.
42 . The engine exhaust catalyst according to claim 5 , wherein the promoter comprises bismuth.
43 . The engine exhaust catalyst according to claim 2 , wherein the supported palladium-gold catalyst has a palladium to gold weight ratio range of about 0.05:1 to 1:0.05.
44 . The engine exhaust catalyst according to claim 7 , wherein the second supported catalyst has a palladium to gold weight ratio range of about 0.5:1 to about 1:0.5.
45 . The engine exhaust catalyst according to claim 8 , wherein the second supported catalyst has a palladium to gold weight ratio range of about 0.84:1.0.
46 . The engine exhaust catalyst according to claim 1 , wherein the coating further comprises bismuth.
47 . A vehicle emission control system comprising:
an engine exhaust catalyst for treating an exhaust flow from a vehicle engine, the engine exhaust catalyst having a monolithic substrate and a supported catalyst including metal particles consisting essentially of palladium and gold species, coated onto the monolithic substrate; and
a tail pipe through which the exhaust flow treated by the engine exhaust catalyst is discharged to the atmosphere.
48 . The vehicle emission control system according to claim 11 , further comprising a catalytic converter, wherein the engine exhaust catalyst forms a part of the catalytic converter.
49 . The vehicle emission control system according to claim 11 , wherein the engine exhaust catalyst further comprises another supported catalyst coated onto the monolithic substrate.
50 . The vehicle emission control system according to claim 13 , wherein said another supported catalyst promotes the oxidation of NO and/or HC in the exhaust flow.
51 . The vehicle emission control system according to claim 13 , wherein said another supported catalyst comprises a platinum-based catalyst.
52 . The vehicle emission control system according to claim 15 , wherein the platinum-based catalyst comprises platinum and one or more other metals.
53 . The vehicle emission control system according to claim 16 , wherein the platinum-based catalyst comprises platinum and palladium.
54 . The vehicle emission control system according to claim 17 , wherein the platinum-based catalyst comprises platinum and a promoter.
55 . The vehicle emission control system according to claim 18 , wherein the promoter comprises bismuth.
56 . The vehicle emission control system according to claim 11 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.05:1 to 1:0.05.
57 . The vehicle emission control system according to claim 20 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.5:1 to about 1:0.5.
58 . The vehicle emission control system according to claim 21 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.84:1.0.
59 . The vehicle emission control system according to claim 11 , wherein the supported catalyst further includes platinum.
60 . The vehicle emission control system according to claim 23 , wherein the supported catalyst further includes bismuth.
61 . A method for preparing an engine exhaust catalyst, comprising the steps of:
preparing a first supported catalyst comprising a catalyst metal;
preparing a second supported catalyst comprising metal particles consisting essentially of palladium and gold species;
mixing the first supported catalyst and the second supported catalyst in a solvent to form a slurry; and
coating a substrate with slurry.
62 . The method according to claim 25 , wherein the first supported catalyst comprises platinum.
63 . The method according to claim 26 , wherein the first supported catalyst comprises platinum and palladium.
64 . The method according to claim 27 , wherein the first supported catalyst comprises platinum and a promoter.
65 . The method according to claim 28 , wherein the promoter comprises bismuth.
66 . The method according to claim 25 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.05:1 to 1:0.05.
67 . The method according to claim 30 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.5:1 to about 1:0.5.
68 . The method according to claim 31 , wherein the supported catalyst containing palladium and gold species has a palladium to gold weight ratio range of about 0.84:1.0.
69 . The method according to claim 25 , wherein the supported catalyst containing palladium and gold species comprises a promoter.
70 . The method according to claim 33 , wherein the promoter comprises bismuth.