Exhaust gas purifying catalyst

Patent metadata

Field	Value
Publication number	US-9724644-B2
Application number	US-201415037070-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 9, 2013
Publication date	Aug 8, 2017
Grant date	Aug 8, 2017

Abstract

The exhaust gas-purifying catalyst of the invention includes a noble metal, and crystallites that form CZ composite metal particles which serve as a carrier supporting the noble metal and contain at least zirconium (Zr) and cerium (Ce). The CZ composite oxide particles (crystallites) further contain crystal growth-suppressing fine particles which are fine metal particles comprising primarily a metallic element M that melts at 1,500° C. or above and which suppress crystal growth by the CZ composite oxide particles. The content of the metallic element M included in the CZ composite oxide particles, expressed in terms of the oxide thereof, is 0.5 mol % or less of the total oxide.

First claim

The invention claimed is:

1. An exhaust gas-purifying catalyst that is disposed in an exhaust pipe for an internal combustion engine and purifies exhaust gases discharged from the internal combustion engine, comprising:
a noble metal and crystallites that form CZ composite oxide particles which serve as a carrier supporting the noble metal and contain at least zirconium (Zr) and cerium (Ce), wherein
the CZ composite oxide particles (crystallites) further contain crystal growth-suppressing fine particles which comprise primarily a metallic element M that melts at 1,500° C. or above and suppress crystal growth of the CZ composite oxide particles, and
the content of the metallic element M included in the CZ composite oxide particles, expressed in terms of the oxide thereof, is 0.5 mol % or less of the total oxide.

2. The exhaust gas-purifying catalyst according to claim 1 , wherein the metallic element M is of at least one type selected from the group consisting of elements belonging to Groups 5 to 10 and Periods 5 and 6 of the periodic table.

3. The exhaust gas-purifying catalyst according to claim 1 , wherein the metallic element M is a metallic element for which the melting point of uncombined metal composed of element M is at least 2,000° C.

4. The exhaust gas-purifying catalyst according to claim 1 , wherein the metallic element M is of at least one type selected from the group consisting of Nb, Mo, Ta and W.

5. The exhaust gas-purifying catalyst according to claim 1 , wherein the content of the metallic element M included in the CZ composite oxide particles, expressed in terms of the oxide thereof, is from 0.005 mol % to 0.1 mol % of the total oxide.

6. The exhaust gas-purifying catalyst according to claim 1 , wherein the correlation coefficient σ (Ce, M) calculated from formula (1) below is 0.6 or more:

[

Formula
⁢

⁢
1

]

⁢

σ
⁡

(

Ce
,
M

)

=

1
25

×

∑

n
=
1

25

⁢

[

{

I
Ce

⁡

(
n
)

-

I
Ce

⁡

(
Av
)

}

×

{

I
M

⁡

(
n
)

-

I
M

⁡

(
Av
)

}

]

1
25

×

∑

n
=
1

25

⁢

[

I
Ce

⁡

(
n
)

-

I

Assignees

• Cataler Corp

Inventors

• Matsueda Satoshi
• Hirai Akimasa
• Taki Kenichi

Classifications

• B01D2255/207

  Transition metals · CPC title

• B01D2255/20769

  Molybdenum · CPC title

• B01D53/945 Primary

  characterised by a specific catalyst · CPC title

• B01J23/002

  Mixed oxides other than spinels, e.g. perovskite · CPC title

• B01J23/6486

  Tantalum · CPC title