Ce—Zr composite oxide and exhaust gas purification catalyst using same
AssigneeUmicore Shokubai Japan Co., Ltd.
InventorDaishi Fujino
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Abstract
A Ce—Zr composite oxide contains cerium and zirconium, wherein an uneven distribution ratio of cerium atoms is 1.80 or less. A method for producing a Ce—Zr composite oxide includes an acid treatment step of bringing at least one selected from the group consisting of sulfuric acid, nitric acid, and hydrochloric acid, in an amount of 4 to 28 parts by mass with respect to 100 parts by mass of the raw material composite oxide, into contact with the surface of a raw material composite oxide containing cerium and zirconium, and a calcination step of calcining the treated composite oxide obtained in the acid treatment step at 400 to 1200° C. for 5 to 300 minutes.
Claims15
An exhaust gas purification catalyst, comprising:
- a Ce—Zr composite oxide comprising cerium and zirconium with an uneven distribution ratio of cerium atoms that is 1.80 or less;
- and a precious metal, each of which is supported on a three-dimensional structure, wherein the uneven distribution ratio is calculated, relative to the Ce—Zr composite oxide in a state where the Ce—Zr composite oxide has been aged at 1000° C. for 10 h in a nitrogen gas stream containing 10 vol.-% of water vapor, according to the following formula:
- Uneven
-
- distribution
-
- ratio
-
- of
-
- cerium
-
- atoms
- =
- {
- X
- 1
- -
- (
- X
- 1
- +
- X
- 2
- )
- 2
- }
- 2
- +
- {
- X
- 2
- -
- (
- X
- 1
- +
- X
- 2
- )
- 2
- }
- 2
- wherein X1 equals the surface Ce ratio (X1) measured according to ISO 10810, and X2 equals the internal Ce ratio (X2) measured according to ISO 15969 (sputtering method), and
- wherein the Ce—Zr composite oxide has a surface residual ratio of cerium atoms of 0.91 or more and 1.00 or less.
Dependencies are inferred from the claim text.