Exhaust system comprising a catalyst with a downstream filter and SCR catalyst

摘要

A method of treating nitrogen oxides NOx and particulate matter PM comprises the steps of catalytically converting nitrogen monoxide NO to nitrogen dioxide NO2 using a catalyst composition comprising a manganese oxide and at least one platinum group metal, converting NOx to nitrogen N2, by contacting a mixture of NO and NO2 with a nitrogenous reducing agent in the presence of a selective catalytic reduction SCR catalyst, and filtering PM to combust it in NO2. The catalyst composition may also comprise cerium oxide. An exhaust system is also claimed comprising a catalysed soot filter CSF with a portion of its substrate being catalysed and having an SCR downstream of it, where the catalyst on the substrate comprises a manganese oxide and at least one platinum group metal.