# US 7,608,561 B2 · Exhaust gas purifying catalyst

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- Number: US 7,608,561 B2
- Document ID: US7608561B2
- Status: Granted
- Kind: B2
- Application number: 11/546,340
- Filed: 2006-10-12
- Published: 2007-04-26
- Granted: 2009-10-27
- Earliest claimed: 2005-10-26
- Assignees: Mazda Motor Corporation
- Inventors: Seiji Miyoshi; Hiroshi Yamada; Koji Minoshima; Akihide Takami; Hideharu Iwakuni
- Web page: https://patentgrep.com/patent/US7608561B2

## CPC

- B01D 53/945: {characterised by a specific catalyst}
- B01J 21/066: {Zirconium or hafnium; Oxides or hydroxides thereof}
- B01J 23/002: {Mixed oxides other than spinels, e.g. perovskite}
- B01J 23/63: with rare earths or actinides
- B01J 35/57: Honeycombs
- B01J 37/0244: {Coatings comprising several layers}
- C01G 25/00: Compounds of zirconium
- C01G 25/006: {Compounds containing zirconium, with or without oxygen or hydrogen, and containing two or more other elements}
- B01D 2255/1025: Rhodium
- B01D 2255/407: Zr-Ce mixed oxides
- C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram
- 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
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An exhaust gas purifying catalyst comprising: a honeycomb-like substrate disposed in an exhaust passage for an engine; and a catalytic layer formed on a cell wall of said substrate, said catalytic layer including a mixed oxide which contains Ce (cerium) and Zr (zirconium), and retains a catalytic noble metal in such a manner that said noble metal atoms are located at crystal lattice points or between the lattice points of the mixed oxide, wherein said mixed oxide includes a first mixed oxide containing CeO2 in a mass greater than that of ZrO2, and a second mixed oxide containing ZrO2 in a mass greater than that of CeO2.

## Claims

### Claim 1

An exhaust gas purifying catalyst comprising:
a honeycomb substrate disposed in an exhaust passage for an engine; and
a catalytic layer formed on a cell wall of said substrate, said catalytic layer including a mixed oxide which contains Ce (cerium) and Zr (zirconium), and retains a catalytic noble metal in such a manner that said noble metal atoms are located at crystal lattice points or between the lattice points of the mixed oxide, wherein
said mixed oxide includes a first mixed oxide containing CeO2 in a mass greater than that of ZrO2, and a second mixed oxide containing ZrO2 in a mass greater than that of CeO2,
wherein said first mixed oxide contains CeO2 in 65 mass % or more with respect to a total mass of CeO2, and ZrO2;
said second mixed oxide contains ZrO2 in 65 mass % or more with respect to a total mass of CeO2 and ZrO2, and
wherein said catalytic layer comprises a plurality of layers having a laminated structure, at least one of said layers containing said first mixed oxide, and at least one of the remaining layers containing said second mixed oxide.

### Claim 2 (depends on 1)

The exhaust gas catalyst as defined in claim 1, wherein a mass ratio of said first mixed oxide with respect to said second mixed oxide is set in a range of 25/75 to 75/25 inclusive.

### Claim 3 (depends on 2)

The exhaust gas purifying catalyst as defined in claim 2, wherein the layer containing the first mixed oxide is formed as an upper layer while the layer containing the second mixed oxide is formed as a lower layer.

### Claim 4 (depends on 1)

The exhaust gas purifying catalyst as defined in claim 1, wherein the layer containing the first mixed oxide is formed as an upper layer while the layer containing the second mixed oxide is formed as a lower layer.

### Claim 5 (depends on 1)

The exhaust gas purifying catalyst as defined in claim 1, wherein said catalyst noble metal includes at least Rh.