# US 5,702,675 A · Catalyst for purifying exhaust gases and process for producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,702,675 A - Document ID: US5702675A - Status: Granted - Kind: A - Application number: 08/571,638 - Filed: 1995-12-13 - Granted: 1997-12-30 - Earliest claimed: 1994-12-16 - Assignees: Toyota Jidosha Kabushiki Kaisha - Inventors: Shinichi Takeshima; Toshiaki Tanaka; Satoshi Iguchi - Web page: https://patentgrep.com/patent/US5702675A ## CPC - B01D 53/9481: {Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start} - B01D 53/945: {characterised by a specific catalyst} - B01J 23/58: with alkali- or alkaline earth metals - B01J 23/63: with rare earths or actinides - B01J 37/0244: {Coatings comprising several layers} - F01N 3/0842: {Nitrogen oxides} - Y02T 10/12: Improving ICE efficiencies - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A catalyst for purifying exhaust gases, which is composed of a catalyst substrate, a first porous support layer supporting barium as a NOx-occluding material and palladium, which is formed on the catalyst support, and a second porous support layer supporting platinum, which is formed on the first porous support layer. Platinum efficiently oxidizes nitrogen monoxide to be converted into nitrogen dioxide. Palladium is supported in a highly dispersed state even after endurance to act as inlet and outlet of barium for nitrogen dioxide or the like, whereby absorption and emission of nitrogen oxides can be performed smoothly, and accordingly, the purification performance for nitrogen oxides is improved. ## Claims ### Claim 1 A process for purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gases in oxygen-rich atmosphere, thereby purifying the exhaust gases, the process comprising: bringing exhaust gases in oxygen-rich atmosphere, whose oxygen concentration is more than required for oxidizing the components to be oxidized therein, into contact with a catalyst: the catalyst comprising: a catalyst substrate; a first porous support layer consisting essentially of first porous support supporting palladium and at least one kind of NOx-occluding material selected from the group consisting of alkali metals, alkaline earth metals and rare earth elements, and formed on a surface of said catalyst substrate; and a second porous support layer comprising a second porous support supporting at least platinum, and formed on a surface of said first porous support layer, and wherein said second porous support layer supports no components having oxygen-occluding ability. ### Claim 2 (depends on 1) The process as claimed in claim 1, wherein said first porous support and second porous support are selected from the group consisting of alumina, silica, silica-alumina, and titania. ### Claim 3 (depends on 2) The process as claimed in claim 2, wherein said first porous support and second porous support are alumina. ### Claim 4 (depends on 1) The process as claimed in claim 1, wherein a content of said palladium is 0.2 to 40 g per 100 g of material of said first porous support layer. ### Claim 5 (depends on 1) The process as claimed in claim 1, wherein a content of said palladium is 1 to 20 g per 100 g of material of said first porous support layer. ### Claim 6 (depends on 1) The process as claimed in claim 1, wherein rhodium is further supported on said second porous support layer. ### Claim 7 (depends on 1) The process as claimed in claim 1, wherein a content of said NOx-occluding material is 0.05 to 1.0 moles per 100 g of material of said first porous support layer. ### Claim 8 (depends on 1) The process as claimed in claim 1, wherein a thickness of said second porous support layer is 10 to 100 .mu.m. ### Claim 9 A process for purifying carbon monoxide, hydrocarbons and nitrogen oxides in exhaust gases in oxygen-rich atmosphere, thereby purifying the exhaust gases, the process comprising: bringing exhaust gases in oxygen-rich atmosphere, whose oxygen concentration is more than required for oxidizing the components to be oxidized therein, into contact with a catalyst: the catalyst comprising: a catalyst substrate; a first porous support layer consisting essentially of a first porous support supporting palladium, at least one kind of NOx-occluding material selected from the group consisting of alkali metals, alkaline earth metals and rare earth elements, and at least one component having oxygen-occluding ability, wherein said first porous support layer is formed on a surface of said catalyst substrate; and a second porous support layer comprising a second porous support supporting at least platinum, wherein said second porous support layer is formed on a surface of said first porous support layer, and wherein said second porous support layer supports no components having oxygen-occluding ability. ### Claim 10 (depends on 9) The process as claimed in claim 9, wherein said component having oxygen-occluding ability in said first porous support layer is ceria. ### Claim 11 (depends on 10) The process as claimed in claim 10, wherein a content of said ceria is 0.05 to 1.0 moles per 100 g of material of said first porous support layer. ### Claim 12 (depends on 10) The process as claimed in claim 10, wherein a content of said ceria is 0.1 to 0.5 moles 100 g of material of said first porous support layer.