Three-way catalyst washcoat loading of particulate filter

摘要

A catalysed exhaust filter (e.g. a DPF) 20 for an internal combustion engine 13. The filter comprises a porous substrate having a total substrate length, and inlet and outlet surfaces. The porous substrate is coated with a three-way catalyst washcoat comprising at least one precious metal selected from the group consisting of (i) platinum and rhodium; (ii) palladium and rhodium; and (iii) platinum, palladium and rhodium, supported on a high surface area oxide, and an oxygen storage component. The washcoat is axially arranged on the porous substrate between a first zone 22 comprising the inlet surfaces and of a first substrate length less than the total substrate length, and a second zone 24 comprising the outlet surfaces and of a second substrate length less than the total substrate length. The sum of the substrate length in the first and second zones is greater than or equal to 100%. A washcoat and/or precious metal loading in the first zone is/are greater than in the second zone.