Exhaust gas purifying catalyst

• US 6,825,145 B2
• Filed: 06/02/2003
• Issued: 11/30/2004
• Est. Priority Date: 07/17/2000
• Status: Active Grant

• Current Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Original Assignee: Mitsubishi Jidosha Kogyo Kabushiki Kaisha
• Inventors: Nakayama, Osamu, Iwachido, Kinichi, Tashiro, Keisuke, Tanada, Hiroshi, Watanabe, Tetsuya, Koga, Kazuo
• Primary Examiner(s): Nguyen, Cam N.
• Application Number:
  US10/452,206
• Publication Number:
  US 20030211939A1
• Time in Patent Office: 547 Days
• Field of Search: 502/64, 502/305, 502/308, 502/309, 502/310, 502/311, 502/312, 502/317, 502/320, 502/322, 502/323, 502/344, 502/349, 502/351, 502/352, 502/354-355, 502/527.12, 502/527.13
• US Class Current: 502/64
• CPC Class Codes: B01D 2255/102 Platinum group metals
• CPC Class Codes: B01D 2255/202 Alkali metals
• CPC Class Codes: B01D 2255/204 Alkaline earth metals
• CPC Class Codes: B01D 2255/30 Silica
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/91 NOx-storage component incorporated in the catalyst
• CPC Class Codes: B01D 53/9422 for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR)
• CPC Class Codes: B01D 53/945 characterised by a specific catalyst
• CPC Class Codes: B01D 53/9468 in different layers
• CPC Class Codes: B01J 23/58 with alkali- or alkaline earth metals
• CPC Class Codes: B01J 29/082 X-type faujasite
• CPC Class Codes: B01J 29/084 Y-type faujasite
• CPC Class Codes: B01J 29/18 of the mordenite type
• CPC Class Codes: B01J 29/40 of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
• CPC Class Codes: B01J 29/70 of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
• CPC Class Codes: B01J 37/0244 Coatings comprising several layers
• CPC Class Codes: B01J 37/0246 Coatings comprising a zeolite
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies

Abstract

The present invention provides an exhaust gas purifying catalyst that is capable of substantially reducing the degree of deterioration in an exhaust gas purifying capability, which results from dissipation of an absorbent agent. Accordingly, an exhaust gas purifying catalyst, which includes a carrier and a catalyst layer, and to which at least one material selected from a group of alkali metals and alkali earth metals is added as an absorbent agent, is characterized in that acid material with a high affinity with respect to the absorbent agent is mixed in the catalyst layer so as to fix the absorbent agent, and an inhibiting layer is formed between the catalyst layer and the carrier so as to inhibit the movement of the absorbent agent toward the carrier.

Claims

1. An exhaust gas purifying catalyst comprising:

a carrier;

a catalyst layer; and

an inhibiting layer formed between said catalyst layer and said carrier;

wherein at least one material selected from alkali metals is contained in the catalyst layer as an absorbent agent;

wherein an acid material with a high affinity with respect to said absorbent agent is mixed in said catalyst layer; and

wherein the inhibiting layer inhibits movement of said absorbent agent toward said carrier.

2. An exhaust gas purifying catalyst according to claim 1, further comprising:

a second catalyst layer formed on an external surface of said catalyst layer; and

wherein at least one material selected from alkali metals contained in the second catalyst layer as an absorbent agent.

3. An exhaust gas purifying catalyst according to claim 1, further comprising:

a second catalyst layer formed between said catalyst layer and said inhibiting layer; and

wherein at least one material selected from alkali metals contained in the second catalyst layer as an absorbent agent.

4. An exhaust gas purifying catalyst according to claim 1, wherein said acid material or said inhibiting layer is composed of at least one of the following materials:

an acid oxide including at least one acid substance selected from a group consisting of Group-IV, Group-V and Group-VI transition elements, and Group-IV, Group-V and Group-VI non-transition elements;

a complex oxide including said at least one acid substance;

a material that does not inhibit reaction of a nitrogen oxide and said absorbent agent; and

a material that absorbs a reduced substance.

5. An exhaust gas purifying catalyst according to claim 1,

wherein said acid material is composed of zeolite;

and

wherein said inhibiting layer is composed of silica (SiO₂).

6. An exhaust gas purifying catalyst according to claim 1, wherein said inhibiting layer is composed of at least one of the following materials:

a layer with a high acidity,

a layer with a large specific surface area,

a layer with a small crystal lattice,

a layer composed of a compound, and

a layer with a high alkalinity.

7. An exhaust gas purifying catalyst according to claim 1,

wherein said absorbent agent includes potassium (K);

and

wherein said carrier is composed of a porous carrier.

8. A method of manufacturing an exhaust gas purifying catalyst comprising:

forming a carrier;

forming an inhibiting layer on the carrier; and

forming a catalyst layer on the inhibiting layer;

wherein at least one material selected from alkali metals is added to the catalyst layer as an absorbent agent;

wherein an acid material with a high affinity with respect to said absorbent agent is mixed in said catalyst layer; and

wherein the inhibiting layer inhibits movement of said absorbent agent toward said carrier.

9. A method of manufacturing an exhaust gas purifying catalyst according to claim 8, further comprising:

forming a second catalyst layer on an external surface of said catalyst layer; and

wherein at least one material selected from alkali metals is added to the second catalyst layer as an absorbent agent.

10. A method of manufacturing an exhaust gas purifying catalyst according to claim 8, further comprising:

forming a second catalyst layer between said catalyst layer and said inhibiting layer; and

wherein at least one material selected from alkali metals is added to the second catalyst layer as an absorbent agent.

11. A method of manufacturing an exhaust gas purifying catalyst according to claim 8, wherein said acid material or said inhibiting layer is composed of at least one of the following materials:

an acid oxide including at least one acid substance selected from a group consisting of Group-IV, Group-V and Group-VI transition elements, and Group-IV, Group-V and Group-VI non-transition elements;

a complex oxide including said at least one acid substance;

a material that does not inhibit reaction of a nitrogen oxide and said absorbent agent; and

a material that absorbs a reduced substance.

12. A method of manufacturing an exhaust gas purifying catalyst according to claim 8,

wherein said acid material is composed of zeolite;

and

wherein said inhibiting layer is composed of silica (SiO₂).

13. A method of manufacturing an exhaust gas purifying catalyst according to claim 8, wherein said inhibiting layer is composed of at least one of the following materials:

a layer with a high acidity,

a layer with a large specific surface area,

a layer with a small crystal lattice,

a layer composed of a compound, and

a layer with a high alkalinity.

14. A method of manufacturing an exhaust gas purifying catalyst according to claim 8,

wherein said absorbent agent includes potassium (K);

and

wherein said carrier is composed of a porous carrier.