Catalyst for purifying exhaust gas

• US 7,759,283 B2
• Filed: 07/24/2007
• Issued: 07/20/2010
• Est. Priority Date: 07/25/2006
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: DENSO Corporation, Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Yamato, Masanori, Shinyoshi, Takatoshi, Ito, Keiji, Suzawa, Takumi
• Primary Examiner(s): Nguyen; Cam N
• Application Number:
  US12/375,013
• Publication Number:
  US 20090239745A1
• Time in Patent Office: 1,092 Days
• Field of Search: 502/326, 502/327, 502/332, 502/333, 502/334, 502/339, 502/415, 502/439, 502/527.12, 502/527.13, 502/527.19, 502/261, 502/262
• US Class Current: 502/339
• CPC Class Codes: B01D 2255/908 O2-storage component incorporated in the catalyst
• CPC Class Codes: B01D 53/944 Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts three-way-catalysts [TWC] B01D53/9445
• CPC Class Codes: B01J 23/63 with rare earths or actinides
• CPC Class Codes: B01J 37/0244 Coatings comprising several layers
• CPC Class Codes: B01J 37/0248 Coatings comprising impregnated particles
• CPC Class Codes: F01N 2260/06 for improving exhaust evacuation or circulation, or reducing back-pressure
• CPC Class Codes: F01N 2330/06 Ceramic, e.g. monoliths
• CPC Class Codes: F01N 2510/0682 having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
• CPC Class Codes: F01N 2510/0684 having more than one coating layer, e.g. multi-layered coatings
• CPC Class Codes: F01N 3/0864 Oxygen
• CPC Class Codes: F01N 3/103 Oxidation catalysts for HC and CO only
• CPC Class Codes: F01N 3/2842 specially adapted for monolithic supports, e.g. of honeycomb type F01N3/2853 - F01N3/2871 take precedence
• CPC Class Codes: Y10T 428/24149 Honeycomb-like

Abstract

To improve a CO conversion in stoichiometry-lean atmosphere, and additionally to prevent the rise of pressure loss.

A catalytic coating layer 2 is constituted of a lower layer 20 including an oxygen storage capacity material and an upper layer 21 being formed on a surface of the lower layer 20 and including a catalytic noble metal, and a thickness of the upper layer is adapted so as to be 5 μm-40 μm. The upper layer 21 is good in terms of gas diffusibility, and thereby OSC resulting from the oxygen storage capacity material being included in the lower layer 20 is demonstrated maximally.

Claims

1. A catalyst for purifying exhaust gas, comprising:

a honeycomb-shaped structure having a plurality of cellular passages demarcated by a plurality of cellular partition walls; and

a catalytic coating layer defined on a surface of the cellular partition walls;

wherein the catalytic coating layer comprises a lower layer containing an oxygen storage capacity material and an upper layer defined on a surface of the lower layer and containing a catalytic noble metal;

at least 90% of the catalytic coating layer exhibits a total thickness in a range of 10 μ

m-80 μ

m;

a thickness of the upper layer is 5 μ

m-40 μ

m;

a first catalytic noble metal being at least one member selected from the group consisting of Pt, Pd and Rh is loaded onto the upper layer; and

a second catalytic noble metal is loaded onto the lower layer, the second catalytic noble metal being a catalytic noble metal different from the first catalytic noble metal.

2. The catalyst for purifying exhaust gas set forth in claim 1, wherein the thickness of said upper layer is 30 μ

m or less.

3. The catalyst for purifying exhaust gas set forth in claim 1, wherein:

Rh is loaded onto said upper layer; and

at least one of Pt and Pd is loaded onto said lower layer.