Oxidation catalyst for a combustion engine
View Patent ↗An oxidation catalyst for treating an exhaust gas produced by a combustion engine, wherein the oxidation catalyst comprises a substrate and a catalyst layer, wherein the catalyst layer comprises: a first support material; a first noble metal; and a second noble metal; wherein the catalyst layer is disposed on a surface of the substrate, and the catalyst layer has a non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate. The oxidation catalyst can be used to oxidize carbon monoxide (CO), hydrocarbons (HCs) and also oxides of nitrogen (NO x ) in such an exhaust gas.
1. An oxidation catalyst for treating an exhaust gas produced by a combustion engine, wherein the oxidation catalyst comprises a substrate and a catalyst layer, wherein the catalyst layer comprises:
a first support material;
a first noble metal; and
a second noble metal;
wherein the catalyst layer is disposed on a surface of the substrate, and the catalyst layer has a non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate, wherein the non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate is either (a) a gradated distribution of the first noble metal or (b) a step-wise distribution of the first noble metal.
2. An oxidation catalyst according to claim 1 , wherein the amount of the first noble metal increases in a perpendicular direction toward the surface of the substrate.
3. An oxidation catalyst according to claim 1 , wherein the amount of the first noble metal decreases in a perpendicular direction toward the surface of the substrate.
4. An oxidation catalyst according to claim 3 , wherein the catalyst layer has a first surface and a second surface, and at least 60% of the total amount of the first noble metal is distributed between the first surface and a plane in the catalyst layer that is half way between the first surface and the second surface.
5. An oxidation catalyst according to claim 1 , wherein the first noble metal is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, silver and gold.
6. An oxidation catalyst according to claim 5 , wherein the first noble metal is palladium.
7. An oxidation catalyst according to claim 1 , wherein the first support material comprises a refractory oxide selected from the group consisting of alumina, magnesia, silica, zirconia, titania, ceria and a composite oxide or a mixed oxide of two or more thereof.
8. An oxidation catalyst according to claim 1 , wherein the second noble metal is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, silver and gold.
9. An exhaust system for a combustion engine comprising an oxidation catalyst according to claim 1 , and at least one emissions control device.
10. A method of treating an exhaust gas produced by an internal combustion engine, which method comprises contacting the exhaust gas with an oxidation catalyst, wherein the oxidation catalyst comprises a substrate and a catalyst layer, wherein the catalyst layer comprises:
a first support material;
a first noble metal; and
a second noble metal;
wherein the catalyst layer is disposed on a surface of the substrate and has a non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate, wherein the non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate is either (a) a gradated distribution of the first noble metal or (b) a step-wise distribution of the first noble metal.
11. An oxidation catalyst for treating an exhaust gas produced by a combustion engine, wherein the oxidation catalyst comprises a substrate and a catalyst layer, wherein the catalyst layer comprises:
a first support material;
a first noble metal; and
a second noble metal;
wherein the catalyst layer is disposed on a surface of the substrate, and the catalyst layer has a non-uniform distribution of the first noble metal in a direction perpendicular to the surface of the substrate, wherein the amount of the first noble metal either (a) increases in a perpendicular direction toward the surface of the substrate or (b) decreases in a perpendicular direction toward the surface of the substrate.
12. An oxidation catalyst according to claim 11 , wherein the catalyst layer has a first surface and a second surface, and at least 60% of the total amount of the first noble metal is distributed between the first surface and a plane in the catalyst layer that is half way between the first surface and the second surface.
13. An oxidation catalyst according to claim 12 , wherein the first noble metal is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, silver and gold.
14. An oxidation catalyst according to claim 13 , wherein the first noble metal is palladium.
15. An oxidation catalyst according to claim 11 , wherein the first support material comprises a refractory oxide selected from the group consisting of alumina, magnesia, silica, zirconia, titania, ceria and a composite oxide or a mixed oxide of two or more thereof.
16. An oxidation catalyst according to claim 11 , wherein the second noble metal is selected from the group consisting of ruthenium, rhodium, palladium, osmium, iridium, platinum, silver and gold.