DIESEL OXIDATION CATALYST AND EXHAUST SYSTEM
An oxidation catalyst for treating an exhaust gas from a diesel engine and an exhaust system comprising the oxidation catalyst are described. The oxidation catalyst comprises: a first washcoat region for oxidising carbon monoxide (CO) and hydrocarbons (HCs), wherein the first washcoat region comprises a first platinum group metal (PGM) and a first support material; a second washcoat region for oxidising nitric oxide (NO), wherein the second washcoat region comprises platinum (Pt), manganese (Mn) and a second support material; and a substrate having an inlet end and an outlet end; wherein the second washcoat region is arranged to contact the exhaust gas at the outlet end of the substrate and after contact of the exhaust gas with the first washcoat region.
1 . An exhaust system for a diesel engine, which comprises an oxidation catalyst for treating an exhaust gas from the diesel engine and an emissions control device, wherein the oxidation catalyst comprises:
a first washcoat zone for oxidising carbon monoxide (CO) and hydrocarbons (HCs), wherein the first washcoat region comprises a first platinum group metal (PGM) and a first support material;
a second washcoat zone for oxidising nitric oxide (NO), wherein the second washcoat zone comprises platinum (Pt) and manganese (Mn) disposed or supported on a second support material, wherein the second support material comprises a refractory metal oxide; and
a substrate, and
wherein the second washcoat zone is disposed at an outlet end of the substrate, and the first washcoat zone disposed at an inlet end of the substrate.
2 . An exhaust system according to claim 1 , wherein the second washcoat zone comprises platinum (Pt) as the only platinum group metal.
3 . An exhaust system according to claim 1 , wherein the second support material comprises a refractory metal oxide selected from the group consisting of alumina, silica, titania, zirconia, ceria and a mixed or composite oxide of two or more thereof.
4 . An exhaust system according to claim 3 , wherein the second support material comprises alumina doped with silica.
5 . An exhaust system according to claim 1 , wherein the first platinum group metal (PGM) is selected from the group consisting of platinum (Pt), palladium (Pd) and a combination thereof.
6 . An exhaust system according to claim 1 , wherein the first support material comprises a refractory metal oxide selected from the group consisting of alumina, silica, titania, zirconia, ceria and a mixed or composite oxide of two or more thereof.
7 . An exhaust system according to claim 6 , wherein the first support material comprises alumina doped with silica.
8 . An exhaust system according to claim 1 , wherein the first washcoat zone further comprises a hydrocarbon adsorbent material, which is a zeolite.
9 . An exhaust system according to claim 8 , wherein the first washcoat zone comprises a total amount of hydrocarbon adsorbent, which is a zeolite, of 0.2 to 3.00 g in −3 .
10 . An exhaust system according to claim 1 , wherein the first washcoat zone further comprises an alkaline earth metal.
11 . An exhaust system according to claim 1 , wherein the first washcoat zone is substantially free of manganese or an oxide thereof.
12 . An exhaust system according to claim 1 , wherein the second washcoat zone does not comprise at least one of rhodium, an alkali metal and an alkaline earth metal.
13 . An exhaust system according to claim 1 , wherein the substrate is a flow-through substrate.
14 . An exhaust system according to claim 1 , wherein the emissions control device is selected from the group consisting of a diesel particulate filter, a selective catalytic reduction catalyst, a catalysed soot filter, a selective catalytic reduction filter catalyst, and combinations of two or more thereof.
15 . A vehicle comprising a diesel engine and an exhaust system as defined in claim 1 .