Catalyzed Soot Filter

A catalyzed soot filter, comprising

• a wall flow substrate comprising an inlet end, an outlet end, a substrate axial length extending between the inlet end and the outlet end, and a plurality of passages defined by internal walls of the wall flow filter substrate;
• wherein the plurality of passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end;
• wherein the internal walls of the inlet passages comprise an inlet coating that extends from the inlet end to an inlet coating end, thereby defining an inlet coating length, wherein the inlet coating length is x % of the substrate axial length, with 0<x≦80;
• wherein the internal walls of the outlet passages comprise an outlet coating that extends from the outlet end to an outlet coating end, thereby defining an outlet coating length,
• wherein the outlet coating length is 100-x % of the substrate axial length;
• wherein the inlet coating length defines an upstream zone of the catalyzed soot filter and the outlet coating length defines a downstream zone of the catalyzed soot filter;
• wherein the inlet coating comprises an oxidation catalyst comprising platinum (Pt);
• wherein the outlet coating comprises an oxidation catalyst comprising Pd,
• wherein the Pt concentration in the outlet coating is lower than the Pt concentration in the inlet coating and wherein the weight ratio of Pt:Pd in the outlet coating is in the range of from 0:1 to 2:1;
• wherein the inlet coating and the outlet coating are present on the wall flow substrate at a coating loading ratio in the range of from 0.5 to 1.5, calculated as ratio of the loading of the inlet coating (in g/inch3 (g/(2.54 cm)3)):loading of the outlet coating (in g/inch3 (g/(2.54 cm)3)).