Exhaust gas purifying catalyst, method for producing same, and exhaust gas purification method using same

Patent metadata

Field	Value
Publication number	US-9566573-B2
Application number	US-201414430769-A
Country	US
Kind code	B2
Filing date	Aug 20, 2014
Priority date	Aug 28, 2013
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

An exhaust gas purify catalyst includes a substrate ( 1 ), an oxidation catalyst layer ( 2 ) formed on the substrate ( 1 ) and containing zeolite and at least one catalytic metal, an LNT layer ( 3 ) formed on the oxidation catalyst layer ( 2 ) and containing an NO x storage material and at least one catalytic metal, and an NO x reduction layer ( 4 ) formed on the LNT layer ( 3 ) and containing Rh acting as a catalytic metal and at least one of alumina or zirconia, wherein the NO x reduction layer ( 4 ) has a larger content of Rh than that in each of the oxidation catalyst layer ( 2 ) and the LNT layer ( 3 ).

First claim

The invention claimed is:

1. An exhaust gas purifying catalyst comprising:
a substrate;
an oxidation catalyst layer formed on the substrate, and containing zeolite and at least one catalytic metal;
a lean NO x trap (LNT) layer formed on the oxidation catalyst layer, and containing an NO x storage material and at least one catalytic metal; and
an NO x reduction layer formed on the LNT layer, and containing Rh acting as a catalytic metal and at least one of alumina or zirconia, wherein
the oxidation catalyst layer includes a first oxidation catalyst layer containing alumina and ceria, and a second oxidation catalyst layer formed on the first oxidation catalyst layer and containing zeolite, and
the NO x reduction layer has a larger content of Rh than in each of the oxidation catalyst layer and the LNT layer.

2. The exhaust gas purifying catalyst of claim 1 , wherein
the LNT layer further contains alumina and ceria.

3. The exhaust gas purifying catalyst of claim 1 , wherein
zeolite in the oxidation catalyst layer has an average particle size of 0.5 μm or more and 4.8 μm or less.

4. The exhaust gas purifying catalyst of claim 2 , wherein
zeolite in the oxidation catalyst layer has an average particle size of 0.5 μm or more and 4.8 μm or less.

5. A method for purifying exhaust gas, the method comprising:
disposing the exhaust gas purifying catalyst of claim 1 upstream of a particulate filter provided for an exhaust gas passage of an engine in a flow direction of exhaust gas;
turning an air-fuel ratio of the exhaust gas lean and allowing the NO x storage material to store NO x in the exhaust gas;
releasing NO x from the NO x storage material when a predetermined amount or more of NO x is stored in the NO x storage material by controlling the engine such that a subsequent injection in which fuel is injected into and supplied to a combustion chamber of the engine in an expansion stroke or an exhaust stroke after a main injection in which fuel is injected into and supplied to the combustion chamber of the engine near a top dead center of a compression stroke is performed to increase HC in the exhaust gas, and turning the air-fuel ratio of the exhaust gas rich;
allowing Rh to reduce and purify the NO x released when the NO x released passes through the NO x reduction layer, and
burning the particulate matters when a predetermined amount or more of particulate matters is deposited on the particulate filter by performing the subsequent injection after the main injection with the air-fuel ratio of the exhaust gas maintained lean, performing oxidative combustion of HC in the exhaust gas by Pt and Pd, and raising a temperature of the exhaust gas flowing into the particulate filter.

6. The exhaust gas purifying catalyst of claim 1 , wherein
the LNT layer contains Rh acting as the catalytic metal.

7. An exhaust gas purifying catalyst comprising:
a substrate;
an oxidation catalyst layer formed on the substrate, and containing zeolite and at least one catalytic metal;
a lean NO x trap (LNT) layer formed on the oxidation catalyst layer, and containing an NO x storage material and at least one catalytic metal; and
an NO x reduction layer formed on the LNT layer, and containing Rh acting as a catalytic metal and at least one of alumina or zirconia, wherein
the LNT layer contains Rh acting as the catalytic metal, and
the NO x reduction layer has a larger content of Rh than in each of the oxidation catalyst layer and the LNT layer.

Assignees

• Mazda Motor

Inventors

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

Classifications

• B01D2255/912

  HC-storage component incorporated in the catalyst · CPC title

• F01N3/18

  characterised by methods of operation; Control · CPC title

• B01J37/0201

  Impregnation · CPC title

• B01J35/0006

  Operations & Transport · mapped topic

• B01D53/9422

  for removing nitrogen oxides by NOx storage or reduction by cyclic switching between lean and rich exhaust gases (LNT, NSC, NSR) · CPC title