Catalyst for purifying exhaust gas and method for production thereof
AssigneeNippon Shokubai Kagaku Kogyo Co., Ltd.
InventorsTomohisa Ohata, Kazuo Tsuchitani, Eiichi Shiraishi, Shinya Kitaguchi
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Abstract
A catalyst for purifying exhaust gas comprises a honeycomb carrier of monolithic structure and a coating layer deposited on the honeycomb carrier and formed with a catalyst composition containing a refractory inorganic oxide in the form of particles possessing and average particle diameter in the range of 0.5 to 20 microns, which refractory inorganic oxide has platinum and/or palladium and rhodium deposited thereon in high concentrations. This catalyst is produced by coating the honeycomb carrier with an aqueous slurry containing the catalyst composition and calcining the coated carrier.
Claims37
A catalyst for purifying exhaust gas comprising a honeycomb carrier of monolithic structure and a coating layer applied on said honeycomb carrier and formed with a catalyst composition comprising (i) a platinum group metal-supporting zirconia produced by depositing said platinum group metal on zirconia powder, (ii) a refractory inorganic oxide and (iii) a rare earth metal oxide, wherein said platinum group metal is at least one member selected from the group consisting of (a) rhodium, (b) combination of rhodium and platinum, (c) combination of rhodium and palladium, and (d) combination of rhodium, platinum and palladium, and is deposited in proportion in the range of 0.5 to 30% by weight on said zirconia powder.
A method for the production of a catalyst for purifying exhaust gas, which comprises coating a honeycomb carrier of monolithic structure with an aqueous slurry containing (i) a platinum group metal-carrying zirconia, (ii) a refractory inorganic oxide and (iii) a rare earth metal oxide and calcining the resultant coating carrier, wherein said platinum group metal is at least one member selected from the group consisting of (a) rhodium, (b) combination of rhodium and platinum, (c) combination of rhodium and palladium, and (d) combination of rhodium, platinum and palladium and is deposited in a proportion in the range of 0.5 to 30% by weight on said zirconia powder.
A catalyst for purifying exhaust gas, consisting essentially of a honeycomb carrier of monolithic structure and a coating layer applied on said honeycomb carrier formed by a catalyst composition consisting of a first refractory inorganic oxide, free of noble metal or rhodium deposited thereon, and at least one second inorganic oxide of the group consisting of
- (A) at least one refractory inorganic oxide selected from the group consisting of
- (a) a refractory inorganic oxide having deposited thereon 5 to 30% by weight of at least one noble metal selected from the the group consisting of platinum and palladium and
- (b) a refractory inorganic oxide having 1 to 20% by weight of rhodium deposited thereon, and
- (B) a refractory inorganic oxide having deposited thereon 5 to 30% by weight of at least one noble metal selected from the group consisting of platinum and palladium, and 1 to 20% by weight of rhodium, said second inorganic oxide being in the form of particles possessing an average particle diameter in the range of 0.5 to 20 microns and being dispersed in the said coating layer, and
- (C) cerium oxide, free of noble metal or rhodium deposited thereon, and provided that where a member of group (C) is selected as a second inorganic oxide, at least one group (A) member or at least one group (B) member also must be present wherein the amount of said second inorganic oxide having deposited thereon noble metal or rhodium is less than about 28.6% by weight of total refractory oxides.
A method for the production of a catalyst for purifying exhaust gas, which consisting essentially of coating a honeycomb carrier of monolithic structure with an aqueous slurry containing a catalyst composition and subsequently calcining the coated carrier, said catalyst composition consisting of a first refractory inorganic oxide free of noble metal or rhodium deposited thereon, and a second inorganic oxide selected from the group consisting of
- (A) at least one refractory inorganic oxide selected from the group consisting of
- (a) a refractory inorganic oxide having deposited thereon 5 to 30% by weight of at least one noble metal selected from the group consisting of platinum and palladium and
- (b) a refractory inorganic oxide having 1 to 20% by weight of rhodium deposited thereon and
- (B) a refractory inorganic oxide having deposited thereon 5 to 30% by weight of at least one noble metal selected from the group consisting of platinum and palladium and 1 to 20% by weight of rhodium, in the form of particles possessing an average particle diameter in the range of 0.5 to 20 microns wherein the amount of said second inorganic oxide having deposited thereon noble metal or rhodium is less than about 28.6% by weight of total refractory oxides.
Dependencies are inferred from the claim text.