| abstract |
An oxidation catalyst 5 for treating an exhaust gas produced by a stoichiometric natural gas (NG) engine comprising a substrate 1, a first region 2 comprising a catalytic material for oxidizing ammonia, and a second region 3 comprising a catalytic material for oxidising hydrocarbon (HC), wherein the catalytic material for oxidising hydrocarbon (HC) comprises a molecular sieve and a platinum group metal (PGM) supported on the molecular sieve, wherein the molecular sieve has a framework comprising silicon, oxygen and optionally germanium. A second aspect relates to an exhaust system comprising the oxidation catalyst and a third aspect relates to an apparatus, such as a vehicle, comprising a stoichiometric gas engine and the oxidation catalyst. The molecular sieve may also have a content of heteroatom T-atoms such as aluminium, boron, gallium, titanium, iron or vanadium. The molecular sieve may be a zeolite with a silica to alumina ration of ≥1200. When the framework of the molecular sieve contains germanium, the germanium may be present in an amount of ≤ 10 mol %. The catalytic material for oxidizing ammonia may comprise a small pore molecular sieve and a TM, or alternatively platinum on a siliceous support such as a zeolite. |