Catalyst for purifying exhaust gases and preparation and use thereof.

摘要

The invention concerns a catalyst for oxidation of hydrocarbons and carbon monoxide and/or reduction of nitrogen oxides. The catalyst consists of a carrier body and on this a catalytical coating, which consists of a washcoat layer containing a support material with a high specific surface area, one or more metal oxides with a promoting effect and at least two catalytically active noble metals within the washcoat or on the washcoat. The catalytical coating consists of at least two washcoat layers containing different amounts of at least one noble metal, in such a way that at least one noble metal is concentrated to more than 50 % by weight of its total amount to at least one of the layers and that at least two noble metals are contained together in at least one of the layers. The invention also concerns a process for the preparation of said catalyst in order to obtain said layers with different composition of noble metals. The invention also concerns the use of said catalyst for purification of exhaust gases from internal combustion engines.