Treatment of monolithic catalyst supports

Claim 1

A method for fabricating a catalyst-coated, ceramic honeycomb structure, wherein the ceramic of said honeycomb structure contains microcracks, comprising the steps of: (a) said honeycomb structure is infiltrated with a fluid containing a fugitive material selected from the group of an aqueous solution of an organic compound, an organic solution of a water insoluble organic compound, a liquid organic compound which can be irreversibly hardened through a chemical or thermal reaction, and a molten, water-insoluble organic compound which exists as a low-vapor pressure solid at ambient temperature to inhibit the entry of a subsequently-applied high surface area washcoat into said microcracks; (b) the organic compound is solidified in the microcracks; solidification of said aqueous solution of an organic compound, said organic solution of a water-insoluble organic compound, said liquid organic compound which can be irreversibly hardened through a chemical or thermal reaction, and said molten, water-insoluble organic compound which exists as a low vapor pressure solid at ambient temperature being achieved through firing in a non-oxidizing atmosphere at a sufficiently high temperature to carbonize it and thereby render it insoluble in water; (c) a high surface area washcoat in the form of an aqueous slurry, which may optionally contain a catalyst-providing material, is applied to said support; (d) the coated support is heated in an oxidizing atmosphere to a temperature sufficient to bind the particles of said washcoat together and to burn out or volatilize said fugitive material from the microcracks; (e) where the washcoat in paragraph (c) does not contain catalyst-providing material, the coated support is impregnated with a solution containing a thermally decomposable compound which can provide a catalyst consisting of a base metal compound and/or metallic particles of a noble metal; and (f) the coated support is heated in an oxidizing or reducing atmosphere to a temperature sufficient to provide a deposit of a catalytically-active base metal compound and/or metallic particles of a noble metal through thermal conversion of the thermally decomposable compound.

Claim 2

A method for fabricating a catalyst-coated, ceramic honeycomb structure, wherein the ceramic of said honeycomb structure contains microcracks, comprising the steps of: (a) said honeycomb structure is infiltrated with a fluid containing a fugitive material selected from the group of an aqueous solution of an organic compound, an organic solution of a water insoluble organic compound, a liquid organic compound which can be irreversibly hardened through a chemical or thermal reaction, and a molten, water-insoluble organic compound which exists as a low-vapor pressure solid at ambient temperature to inhibit the entry of a subsequently-applied high surface area washcoat into said microcracks; (b) the organic compound is solidified in the microcracks; solidification of said aqueous solution of an organic compound, said organic solution of a water-insoluble organic compound, said liquid organic compound which can be irreversibly hardened through a chemical or thermal reaction, and said molten, water-insoluble organic compound which exists as a low vapor pressure solid at ambient temperature being achieved through firing in a non-oxidizing atmosphere at a sufficiently high temperature to carbonize it and thereby render it insoluble in water; (c) a high surface area washcoat in the form of an aqueous slurry, which may optionally contain a catalyst-providing material, is applied to said support; (d) the coated support is heated in an oxidizing atmosphere to a temperature sufficient to bind the particles of said washcoat together and to burn out or volatilize said fugitive material from the microcracks; (e) where the washcoat in paragraph (c) does not contain catalyst-providing material, the coated support is impregnated with a solution containing a thermally decomposable compound which can provide a catalyst consisting of a base metal compound and/or metallic particles of a noble metal; and (f) the coated support is heated in an oxidizing or reducing atmosphere to a temperature sufficient to provide a deposit of a catalytically-active base metal compound and/or metallic particles of a noble metal through thermal conversion of the thermally decomposable compound.