Ceria-zirconia composite oxide, method for producing the same, and catalyst for purifying exhaust gas using the ceria-zirconia composite oxide

Patent metadata

Field	Value
Publication number	US-10112180-B2
Application number	US-201415026760-A
Country	US
Kind code	B2
Filing date	Oct 2, 2014
Priority date	Oct 4, 2013
Publication date	Oct 30, 2018
Grant date	Oct 30, 2018

Abstract

A ceria-zirconia composite oxide includes at least one of lanthanum, yttrium, and praseodymium. A rate of a total content of the at least one rare earth element to a total content of cerium and zirconium is 0.1 at % to 4.0 at %. A content of the rare earth element present in near-surface regions, which are at a distance of less than 50 nm from surfaces of primary particles of the ceria-zirconia composite oxide, accounts for 90 at % or more of the total content of the rare earth element. An average particle size of the primary particles of the ceria-zirconia composite oxide is 2.2 μm to 4.5 μm. After a predetermined durability test, the intensity ratio I(14/29) of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° and the intensity ratio I(28/29) of a diffraction line at 2θ=28.5° to the diffraction line at 2θ=29° respectively satisfy the following conditions:

I (14/29)≥0.02, and

I (28/29)≤0.08.

First claim

The invention claimed is:

1. A ceria-zirconia composite oxide containing a composite oxide of ceria and zirconia, comprising
lanthanum, wherein
a ratio of a total content of lanthanum to a total content of cerium and zirconium in the ceria-zirconia composite oxide is 0.25 atomic % to 2.5 atomic %,
a content of lanthanum present in near-surface regions accounts for 90 atomic % or more of the total content of lanthanum, the near-surface regions being at a distance of less than 50 nm from surfaces of primary particles of the ceria-zirconia composite oxide,
a content ratio of cerium to zirconium in the ceria-zirconia composite oxide is in a range from 43:57 to 48:52 by molar ratio,
an average particle size of the primary particles of the ceria-zirconia composite oxide is 2.2 μm to 4.5 μm, and
an intensity ratio I(14/29) of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° and an intensity ratio I(28/29) of a diffraction line at 2θ=28.5° to the diffraction line at 2θ=29° respectively satisfy the following conditions:
I (14/29)≥0.02; and

I (28/29)≤0.08,

wherein the intensity ratio I(14/29) and the intensity ratio I(28/29) are calculated from an X-ray diffraction pattern of the ceria-zirconia composite oxide, the X-ray diffraction pattern being obtained by an X-ray diffraction measurement using CuKα after heating the ceria-zirconia composite oxide under a temperature condition of 1100° C. in air for 5 hours.

2. A method for producing a ceria-zirconia composite oxide containing a composite oxide of ceria and zirconia, the method comprising:
preparing ceria-zirconia composite oxide powder in which a content ratio of cerium to zirconium is in a range from 43:57 to 48:52 by molar ratio and an average particle size of primary particles of the ceria-zirconia composite oxide powder is 2.2 μm 4.5 μm;
allowing lanthanum to be supported on the ceria-zirconia composite oxide powder; and
firing the ceria-zirconia composite oxide powder on which lanthanum is supported at 600° C. to 1200° C. to obtain the ceria-zirconia composite oxide according to claim 1 .

3. A catalyst for purifying exhaust gas comprising the ceria-zirconia composite oxide according to claim 1 .

Assignees

• Toyota Motor Co Ltd
• Cataler Corp

Inventors

• Morikawa Akira
• Konishi Kae
• Tanabe Toshitaka
• Suda Akihiko
• Miura Masahide
• Chinzei Isao
• Suzuki Hiromasa
• Chiba Akiya
• Iizuka Kosuke

Classifications

• C01F17/32

  oxide or hydroxide being the only anion, e.g. NaCeO2 or MgxCayEuO · CPC title

• C04B2235/3229

  Cerium oxides or oxide-forming salts thereof · CPC title

• C04B2235/656

  characterised by specific heating conditions during heat treatment · CPC title

• B01J23/63

  with rare earths or actinides · CPC title

• B01J37/03

  Precipitation; Co-precipitation · CPC title