Exhaust gas purification catalyst

Patent metadata

Field	Value
Publication number	US-10539056-B2
Application number	US-201615560625-A
Country	US
Kind code	B2
Filing date	Mar 24, 2016
Priority date	Mar 27, 2015
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

An object of the present invention is to provide an exhaust gas purification catalyst which can exhibit high durability and warm-up performance. The present invention relates to an exhaust gas purification catalyst comprising a substrate and a catalyst coating layer formed on the substrate, wherein the catalyst coating layer comprises catalyst particles, the catalyst coating layer having an upstream region extending by 40 to 60% of the entire length of the substrate from an upstream end of the catalyst in the direction of an exhaust gas flow and a downstream region corresponding to the remainder portion of the catalyst coating layer, the composition of the catalyst particle of the upstream region being different from that of the downstream region. The upstream region in the direction of an exhaust gas flow has a structure where a void is included in a large number, and furthermore high-aspect-ratio pores having an aspect ratio of 5 or more account for a certain percentage or more of the whole volume of voids. Thus, the exhaust gas purification catalyst exhibits enhanced purification performance.

First claim

The invention claimed is:

1. An exhaust gas purification catalyst comprising a substrate and a catalyst coating layer formed on the substrate, wherein:
the catalyst coating layer comprises catalyst particles, the catalyst coating layer having an upstream region extending by 40 to 60% of the entire length of the substrate from an upstream end of the catalyst in an exhaust gas flow direction and a downstream region corresponding to the remainder portion of the catalyst coating layer, the composition of the catalyst particle of the upstream region being different from that of the downstream region;
in the upstream region of the catalyst coating layer,
an average thickness of the coating layer is in a range from 25 μm to 160 μm,
a porosity measured by a weight-in-water method is in a range from 50 to 80% by volume, and
high-aspect-ratio pores having an aspect ratio of 5 or more account for 0.5 to 50% by volume of the whole volume of voids, and

the high-aspect-ratio pore has an equivalent circle diameter of from 2 μm to 50 μm in a cross-sectional image of a catalyst coating layer cross section perpendicular to an exhaust gas flow direction and has an average aspect ratio of from 10 to 50.

2. The exhaust gas purification catalyst according to claim 1 , wherein in the upstream region of the catalyst coating layer, the high-aspect-ratio pore is oriented such that an 80% cumulative angle, in a cumulative angle distribution on an angle basis, of an angle (cone angle) between a vector in a longitudinal direction of the high-aspect-ratio pore and a vector in an exhaust gas flow direction of the substrate is in a range from 0 to 45 degrees.

3. The exhaust gas purification catalyst according to claim 1 , wherein a 15% cumulative size, in a cumulative particle size distribution on a cross-sectional area basis, of the catalyst particle contained in the upstream region of the catalyst coating layer is in a range from 3 μm to 10 μm.

4. The exhaust gas purification catalyst according to claim 2 , wherein a 15% cumulative size, in a cumulative particle size distribution on a cross-sectional area basis, of the catalyst particle contained in the upstream region of the catalyst coating layer is in a range from 3 μm to 10 μm.

5. The exhaust gas purification catalyst according to claim 1 , wherein in the upstream region of the catalyst coating layer, an amount of coating is in a range from 50 to 300 g per liter of the volume of the substrate.

6. The exhaust gas purification catalyst according to claim 2 , wherein in the upstream region of the catalyst coating layer, an amount of coating is in a range from 50 to 300 g per liter of the volume of the substrate.

7. The exhaust gas purification catalyst according to claim 3 , wherein in the upstream region of the catalyst coating layer, an amount of coating is in a range from 50 to 300 g per liter of the volume of the substrate.

8. The exhaust gas purification catalyst according to claim 4 , wherein in the upstream region of the catalyst coating layer, an amount of coating is in a range from 50 to 300 g per liter of the volume of the substrate.

9. A method for producing an exhaust gas purification catalyst comprising a substrate and a catalyst coating layer formed on the substrate,
the catalyst coating layer having an upstream region extending by 40 to 60% of the entire length of the substrate from an upstream end of the catalyst in an exhaust gas flow direction and a downstream region corresponding to the remainder portion of the catalyst coating layer, the composition of the upstream region being different from that of the downstream region,
the method comprising the step of forming the upstream region of the catalyst coating layer using a catalyst slurry, wherein
the catalyst slurry comprises:
a noble metal particle having catalyst activity,
a metal oxide particle having a 50% cumulative size of 3 μm to 10 μm in a cumulative particle size distribution on a volume basis, and
a fibrous organic substance in an amount of 0.5 to 9.0 parts by mass based on 100 parts by mass of the metal oxide particle, and

the fibrous organic substance has an average fiber diameter in a range from 1.7 μm to 8.0 μm and an average aspect ratio in a range from 9 to 40.

10. The method according to claim 9 , comprising the step of forming a catalyst coating by coating a surface of the substrate with the catalyst slurry such that an amount of coating of the catalyst coating layer after firing is in a range from 50 to 300 g per liter of the volume of the substrate and that an average thickness of the catalyst coating layer after firing is in a range from 25 μm to 160 μm.

11. The method according to claim 9 , comprising the step of removing at least a part of the fibrous organic substance by firing after coating the surface of the substrate with the catalyst slurry.

12. The method according to claim 10 , comprising the step of removing at least a part of the fibrous organic substance by firing after coating the surface of the substrate with the catalyst slurry.

Assignees

• Toyota Motor Co Ltd
• Cataler Corp

Inventors

• Suzuki Hiromasa
• Miura Masahide
• Saito Yoshinori
• Katoh Satoru
• Tanabe Toshitaka
• Hirao Tetsuhiro
• Ohashi Tatsuya
• Naito Hiroaki
• Ori Hirotaka
• Takeuchi Michihiko
• Narita Keiichi

Classifications

• B01J37/0219

  the coating containing organic compounds · CPC title

• B01D2255/9202

  Linear dimensions · CPC title

• B01D53/94

  by catalytic processes · CPC title

• B01J37/08

  Heat treatment {(B01J37/0009, B01J37/0018 take precedence)} · CPC title

• F01N3/28

  Construction of catalytic reactors · CPC title