Exhaust gas purification catalyst and production method thereof

Patent metadata

Field	Value
Publication number	US-9550176-B2
Application number	US-201414430514-A
Country	US
Kind code	B2
Filing date	Apr 22, 2014
Priority date	May 27, 2013
Publication date	Jan 24, 2017
Grant date	Jan 24, 2017

Abstract

This catalyst includes a lower catalytic layer 2 having catalytic ability to oxidize HC and CO and an upper catalytic layer 3 having catalytic ability to reduce NO x . The lower catalytic layer 2 contains Pt and Pd acting as catalytic metals, zeolite, a Ce-containing oxide, and activated alumina, and the upper catalytic layer 3 contains activated alumina loading an Rh-doped Ce-containing oxide and an NO x storage material.

First claim

The invention claimed is:

1. An exhaust gas purification catalyst comprising:
a lower catalytic layer having catalytic ability to oxidize HC and CO on a substrate; and
an upper catalytic layer having catalytic ability to reduce NO x on top of, or above, the lower catalytic layer, wherein
the lower catalytic layer contains Pt and Pd acting as catalytic metals, zeolite, Ce-containing oxide, and activated alumina,
the upper catalytic layer contains activated alumina loading an Rh-doped Ce-containing oxide and an alkali earth metal acting as an NO x storage material,
the lower catalytic layer includes a first oxidation catalyst layer containing activated alumina loading Pt and Pd and a Ce-containing oxide loading Pt and Pd, and a second oxidation catalyst layer containing zeolite loading Pt and Pd, and
the second oxidation catalyst layer is disposed on the first oxidation catalyst layer.

2. The exhaust gas purification catalyst of claim 1 , wherein
an intermediate catalytic layer is provided between the lower and upper catalytic layers, the intermediate catalytic layer containing Pt and Rh acting as catalytic metals, activated alumina, a Ce-containing oxide and an NOx storage material, and containing no Pd.

3. The exhaust gas purification catalyst of claim 1 , wherein
the substrate has a hexagonal cell honeycomb structure with a hexagonal cell cross section.

4. A method for producing an exhaust gas purification catalyst, the method comprising:
forming, on a substrate, a lower catalytic layer including Pt and Pd acting as catalytic metals, zeolite, a Ce-containing oxide, and activated alumina; and
forming, on the lower catalytic layer, an upper catalytic layer including activated alumina loading an Rh-doped Ce-containing oxide and an alkali earth metal acting as an NO x storage material, wherein
in the forming the upper catalytic layer,
a mixture of a coprecipitated hydroxide containing Ce and Rh, and activated alumina is calcined to prepare the activated alumina loading the Rh-doped Ce-containing oxide, the activated alumina loading the Rh-doped Ce-containing oxide is applied directly or indirectly onto the lower catalytic layer,
the applied layer is impregnated with the NO x storage material, and is calcined, and
in the forming the lower catalytic layer,
a first oxidation catalyst layer containing activated alumina loading Pt and Pd and a Ce-containing oxide loading Pt and Pd is formed on the substrate, and
a second oxidation catalyst layer containing zeolite loading Pt and Pd is formed on the first oxidation catalyst layer.

Assignees

• Mazda Motor

Inventors

• Sato Yoshiyuki
• Yamada Hiroshi
• Harada Koichiro
• Baba Takashi
• Shigetsu Masahiko
• Takami Akihide

Classifications

• B01D2255/50

  Zeolites · CPC title

• B01D53/945

  characterised by a specific catalyst · CPC title

• F01N2370/04

  Zeolitic material · CPC title

• B01J37/0244

  Coatings comprising several layers · CPC title

• B01J37/031

  Precipitation · CPC title