COATINGS ON A MONOLITH ARTICLE
The present disclosure relates to a coated monolith article for filtering particulate matter from exhaust gases. The monolith article has an inlet-end front zone and an outlet-end rear zone, and comprises a zoned and layered coating. The zoned and layered coating comprises an inlet-end front zone which comprises an inorganic oxide coating and an outlet-end rear zone, which contains a layered coating, with the lower layer comprising a washcoat coating and the upper layer comprising an inorganic oxide coating (e.g. an inorganic oxide coating identical to that of the inlet-end front zone). The present disclosure also relates to a method of forming the coated monolith article as described herein and an exhaust system with a coated monolith article as described herein.
1 . A monolith article comprising an inlet-end front zone and an outlet-end rear zone, and a zoned and layered coating, said coating comprises:
c) an inlet-end front zone which comprises an inorganic oxide coating, and
d) an outlet-end rear zone, which comprises a layered coating, with the lower layer comprising a washcoat coating and the upper layer comprising an inorganic oxide coating.
2 . The monolith article according to claim 1 , wherein the inorganic oxide coating of the inlet-end front zone is identical to that of inorganic oxide coating of the upper layer of the outlet-end rear zone.
3 . The monolith article according to claim 1 , wherein the inorganic oxide coating of the inlet end front zone is coated directly onto the monolith article.
4 . The monolith article according to claim 1 , wherein the monolith article is a catalytic wall-flow filter.
5 . The monolith article according to claim 1 , wherein the inorganic oxide coating comprises inorganic particles and a silicone resin.
6 . The monolith article according to claim 1 , wherein the total inorganic oxide coating is present in a mass loading of between 3-15 g/L.
7 . The monolith article according to claim 4 , wherein the ratio of inorganic particles to silicone resin in the inorganic oxide coating is from 1:1 to 4:1.
8 . The monolith article according to claim 1 , wherein the washcoat coating comprises ceria zirconia, alumina, precious metals selected from Pd, Pt or Rh, barium hydroxide, a rheology modifier and a C 2 -C 6 aliphatic amino acid, and wherein the total washcoat loading is from 35 to 150 g/L.
9 . A method of forming a coated monolith article of claim 1 , said method comprising:
v) providing a monolith article which has an inlet-end front zone and an outlet-end rear zone,
vi) applying a washcoat coating to the outlet-end rear zone such that the coating extends from 50-90% of the length of the substrate from the outlet-end rear zone,
vii) optionally drying and/or calcining the washcoat coating,
viii) applying an inorganic oxide coating to the inlet-end front zone such that the coating extends from 50-100% of the length of the substrate from the inlet-end front zone.
10 . The method of claim 9 , wherein the washcoat loading is applied to the monolith article at the outlet-end rear zone of the monolith article in a single dose or in multiple doses, preferably in a single dose or two doses.
11 . The method of claim 9 , wherein the washcoat coating is applied such that it extends from 55 to 85% of the length of the substrate from the outlet-end rear zone.
12 . The method of claim 9 , wherein a mixture of inorganic particles and silicone resin is sprayed as a dry particulate aerosol to from the inorganic oxide coating.
13 . The method of claim 9 , wherein the inorganic oxide coating is applied such that it extends from 55 to 99% of the length of the substrate from the inlet-end front zone.
14 . The method of claim 9 , wherein the method further comprises:
v) drying and calcining the inorganic oxide coating.
15 . An exhaust gas system comprising the coated monolith article claim 1 and a combustion engine.
16 . A method for the treatment of an exhaust gas, the method comprising contacting the exhaust gas with the coated monolith of claim 1 .