Patent ID: 8524182

Claim:
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 a given inlet passage, an adjacent outlet passage, and the internal wall between said inlet and said outlet passage define an overall passage; wherein the internal walls of at least 20% of the overall passages are at least partially coated with a first and a second coating; wherein the internal wall of a given at least partially coated overall passage comprises the first coating that extends from the open inlet end to a first coating end, thereby defining a first coating length, wherein the first coating length is x % of the substrate axial length, with 20≦x≦100; wherein said internal wall of said overall passage further comprises the second coating located downstream of the first coating, said second coating having a second coating length of y % of the substrate axial length, with 20≦y≦100; wherein the first and the second coating overlap in length by at least 20% of the substrate axial length; wherein the first coating comprises an oxidation catalyst comprising platinum (Pt) and optionally palladium (Pd) and wherein the weight ratio of Pt:Pd in the first coating is in the range of from 1:0 to greater than 1:1; wherein the second coating comprises an oxidation catalyst comprising Pd and optionally Pt, wherein the Pt concentration in the second coating is lower than the Pt concentration in the first coating and wherein the weight ratio of Pt:Pd in the second coating is in the range of from 1:1 to 0:1; wherein the first coating and the second coating are present on the wall flow substrate at a coating loading ratio in the range of from 0.25 to 3, calculated as ratio of the loading of the first coating (in g/inch 3 (g/(2.54 cm) 3 )): loading of the second coating (in g/inch 3 (g/(2.54 cm) 3 )).