Catalyst for purifying exhaust gas

• US 7,846,865 B2
• Filed: 07/20/2007
• Issued: 12/07/2010
• Est. Priority Date: 07/20/2006
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kuno, Oji, Yamato, Masanori
• Primary Examiner(s): Nguyen; Cam N
• Application Number:
  US12/373,926
• Publication Number:
  US 20090197764A1
• Time in Patent Office: 1,236 Days
• Field of Search: 502/326, 502/327, 502/332, 502/333, 502/334, 502/339, 502/415, 502/439, 502/527.19, 502/261, 502/262, 502/304, 502/349, 502/350, 502/351
• US Class Current: 502/327
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/1025 Rhodium
• CPC Class Codes: B01D 53/945 characterised by a specific catalyst
• CPC Class Codes: B01D 53/9477 with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: B01J 23/42 Platinum
• CPC Class Codes: B01J 23/464 Rhodium
• CPC Class Codes: B01J 23/63 with rare earths or actinides
• CPC Class Codes: B01J 35/19 Catalysts containing parts with different compositions
• CPC Class Codes: B01J 37/0248 Coatings comprising impregnated particles
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

In the present invention, it is an assignment to optimize a loading density of noble metal on catalyst.

Pt is loaded in such an amount that a loading amount per 1 liter of a support substrate exceeds 0.75 g on an exhaust-gas upstream side of a coating layer, and a loading density of Rh in the coating layer is made so that it becomes higher on an exhaust-gas downstream side than on the exhaust-gas upstream side. The purifying performance after warming up improves by loading Rh with high density on the exhaust-gas downstream side that is likely to become rich atmosphere.

Claims

1. A catalyst for purifying exhaust gas, comprising:

a substrate; and

a coating layer formed on a surface of the substrate,

wherein the coating layer comprises

a porous oxide support; and

noble metals loaded on the porous oxide support, the noble metals including Pt and Rh;

wherein the Pt is loaded in an amount exceeding 0.75 g per 1 liter of the substrate on an exhaust-gas upstream side of the coating layer; and

a loading density of the Rh in the coating layer is higher on an exhaust-gas downstream side than on the exhaust-gas upstream side.

2. A catalyst for purifying exhaust gas, comprising:

a substrate; and

a coating layer formed on a surface of the substrate,

wherein the coating layer comprises

a porous oxide support; and

noble metals loaded on the porous oxide support, the noble metals including Pt and Rh;

wherein the Pt is loaded in an amount exceeding 0.75 g per 1 liter of the substrate on an exhaust-gas upstream side of the coating layer; and

a loading density of the Rh in the coating layer is higher on an exhaust-gas downstream side than on the exhaust-gas upstream side, and

wherein a ratio of a loading amount of Rh on the exhaust-gas upstream side with respect to a loading amount of Rh on the exhaust-gas downstream side is 0.9 or less.

3. The catalyst for purifying exhaust gas set forth in claim 2, wherein the ratio of the loading amount of Rh on the exhaust-gas upstream side with respect to the loading amount of Rh on the exhaust-gas downstream side is 0.5 or less.

4. A catalyst for purifying exhaust gas, comprising:

a substrate; and

a coating layer formed on a surface of the substrate,

wherein the coating layer comprises

a porous oxide support; and

noble metals loaded on the porous oxide support, the noble metals including Pt and Rh;

wherein the Pt is loaded in an amount exceeding 0.75 g per 1 liter of the substrate on an exhaust-gas upstream side of the coating layer;

a loading density of the Rh in the coating layer is higher on an exhaust-gas downstream side than on the exhaust-gas upstream side; and

a loading density of Pt in the coating layer is higher on the exhaust gas upstream side than on the exhaust-gas downstream side.

5. The catalyst for purifying exhaust gas set forth in claim 4, wherein a ratio of a loading amount of Pt on the exhaust-gas upstream side with respect to a loading amount of Pt on the exhaust-gas downstream side is 0.8 or more.

6. The catalyst for purifying exhaust gas set forth in claim 5, wherein the ratio of the loading amount of Pt on the exhaust-gas upstream side with respect to the loading amount of Pt on the exhaust-gas downstream side is 1.4 or more.