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

Patent metadata

Field	Value
Publication number	US-9376327-B2
Application number	US-201113640237-A
Country	US
Kind code	B2
Filing date	Apr 12, 2011
Priority date	Apr 13, 2010
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

A ceria-zirconia base composite oxide contains a composite oxide of ceria and zirconia. In the ceria-zirconia base composite oxide, a content ratio between cerium and zirconium in the composite oxide is in a range from 43:57 to 48:52 in terms of molar ratio ([cerium]:[zirconium]). An intensity ratio of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° {I(14/29) value} and an intensity ratio of a diffraction line at 2θ=28.5° to the diffraction line at 2θ=29° {I(28/29) value}, which are calculated from an X-ray diffraction pattern obtained by an X-ray diffraction measurement using CuKa after heating under a temperature condition of 1100° C. in air for 5 hours, respectively satisfy the following conditions: I(14/29) value≧0.015, and I(28/29) value≦0.08.

First claim

The invention claimed is:

1. A ceria-zirconia base composite oxide comprising a composite oxide of ceria and zirconia, wherein
a content ratio between cerium and zirconium in the composite oxide is in a range from 43:57 to 48:52 in terms of molar ratio ([cerium]:[zirconium]),
an average value (number-based average value) of diameters of crystal grains is 2.2 to 4.5 μm in a field of view (magnification 500×) of a scanning electron microscope, and
an intensity ratio of a diffraction line at 2θ=14.5° to a diffraction line at 2θ=29° {I(14/29) value} and an intensity ratio of a diffraction line at 2θ=28.5° to the diffraction line at 2θ=29° {I(28/29) value}, which are calculated from an X-ray diffraction pattern obtained by an X-ray diffraction measurement using CuKα after heating under a temperature condition of 1100° C. in air for 5 hours, respectively satisfy the following conditions:
I(14/29) value≧0.015, and
I(28/29) value≦0.08.

2. The ceria-zirconia base composite oxide according to claim 1 , wherein a crystal phase having an orderly arranged structure of cerium ions and zirconium ions is formed in the composite oxide.

3. The ceria-zirconia base composite oxide according to claim 1 , wherein an average value of percentages of areas occupied by particles of the composite oxide of ceria and zirconia is 50% or more in a field of view (magnification 500×) of a scanning electron microscope.

4. A method for producing a ceria-zirconia base composite oxide according to claim 1 , the method comprising the step of:
obtaining the ceria-zirconia base composite oxide by compression-molding at a pressure of 40 to 350 MPa (400 to 3500 kgf/cm 2 ) a ceria-zirconia solid solution powder in which a content ratio between cerium and zirconium is in a range from 43:57 to 48:52 in terms of molar ratio ([cerium]:[zirconium]), followed by a reduction treatment under a temperature condition of 1450 to 2000° C.

5. The method for producing a ceria-zirconia base composite oxide according to claim 4 , further comprising a step of, after the reduction treatment,
subjecting the ceria-zirconia base composite oxide to an oxidation treatment.

6. The method for producing a ceria-zirconia base composite oxide according to claim 4 , wherein a crystal phase having an orderly arranged structure of cerium ions and zirconium ions is formed in the composite oxide.

7. The method for producing a ceria-zirconia base composite oxide according to claim 4 , wherein the ceria-zirconia base composite oxide has an average value of percentages of areas occupied by particles being 50% or more in a field of view (magnification 500×) of a scanning electron microscope.

8. A catalyst for purification of exhaust gas, comprising the ceria-zirconia base composite oxide according to claim 1 .

9. The catalyst for purification of exhaust gas according to claim 8 , wherein a crystal phase having an orderly arranged structure of cerium ions and zirconium ions is formed in the composite oxide.

10. The catalyst for purification of exhaust gas according to claim 8 , wherein an average value of percentages of areas occupied by particles of the composite oxide of ceria and zirconia is 50% or more in a field of view (magnification 500×) of a scanning electron microscope.

Assignees

• Morikawa Akira
• Yamamura Kae
• Suda Akihiko
• Takahashi Naoki
• Kuno Oji
• Nobukawa Takeshi
• Chiba Akiya
• Fujii Ryuta
• Toyota Chuo Kenkyusho Kk
• Toyota Motor Co Ltd
• Cataler Corp

Inventors

• Morikawa Akira
• Yamamura Kae
• Suda Akihiko
• Takahashi Naoki
• Kuno Oji
• Nobukawa Takeshi
• Chiba Akiya
• Fujii Ryuta

Classifications

• C01P2002/74

  by peak-intensities or a ratio thereof only · CPC title

• C01G25/00 Primary

  Compounds of zirconium · CPC title

• C04B2235/95

  Products characterised by their size, e.g. microceramics · CPC title

• C01P2004/61

  Micrometer sized, i.e. from 1-100 micrometer · CPC title

• C01P2002/30

  Three-dimensional structures · CPC title