Toyota Jidosha Kabushiki Kaisha

Cataler Corporation

Kosuke Iizuka

Hiromasa Suzuki

Masahide Miura

Akira Morikawa

Akihiko Suda

Toshitaka Tanabe

Isao Chinzei

Akiya Chiba

Kae Konishi

Takeru Yoshida

Hirotaka Ori

Yoshinori Saito

Mitsuyoshi Okada

Takahiro Suzuki

Yuki Aoki

Shogo Shirakawa

Seiji Nakahigashi

Ryota Nakashima

Isao Naito

Minoru Ito

Hiroki Nihashi

Takahiro Nagata

Toshihiro Ikai

A ceria-zirconia-based composite oxide containing a composite oxide of ceria and zirconia is provided, in which primary particles having a particle diameter of 1.5 to 4.5 &#x3bc;m account for, on a particle number basis, at least 50% of all primary particles in the ceria-zirconia-based composite oxide, and the molar ratio of cerium to zirconium in the ceria-zirconia-based composite oxide is between 43:57 and 55:45.

Ceria-zirconia-based composite oxide and method for producing same, and exhaust gas purification catalyst including ceria-zirconia-based composite oxide

The object of the present invention is to provide an exhaust gas purifying catalyst that can achieve high purification performance while suppressing HS emissions. The object is solved by an exhaust gas purifying catalyst in which the lower layer of the catalyst coating layer comprises a ceria-zirconia composite oxide having a pyrochlore-type ordered array structure, in which the ceria-zirconia composite oxide contains at least one additional element selected from the group consisting of praseodymium, lanthanum, and yttrium at 0.5 to 5.0 mol % in relation to the total cation amount, and the molar ratio of (cerium+additional element):(zirconium) is within the range from 43:57 to 48:52.

Exhaust gas purifying catalyst

The object of the present invention is to provide a high-performance exhaust gas purifying catalyst that can achieve oxygen absorption/release capacity and NOx purification performance. The object is solved by an exhaust gas purifying catalyst, which comprises a ceria-zirconia composite oxide having a pyrochlore-type ordered array structure in the upstream part of the catalyst coating layer, in which the ceria-zirconia composite oxide contains at least one additional element selected from the group consisting of praseodymium, lanthanum, and yttrium at 0.5 to 5.0 mol % of the total cation amount, and has a molar ratio of (cerium+the additional element):(zirconium) of 43:57 to 48:52.

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 &#x3bc;m to 4.5 &#x3bc;m. After a predetermined durability test, the intensity ratio I(14/29) of a diffraction line at 2&#x3b8;=14.5&#xb0; to a diffraction line at 2&#x3b8;=29&#xb0; and the intensity ratio I(28/29) of a diffraction line at 2&#x3b8;=28.5&#xb0; to the diffraction line at 2&#x3b8;=29&#xb0; respectively satisfy the following conditions:(14/29)&#x2265;0.02, and(28/29)&#x2264;0.08.

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

An catalyst for purifying exhaust gas comprising an OCS material that has sufficient heat resistance and achieves a favorable balance between the oxygen storage volume and the oxygen absorption/release rate includes an catalyst for purifying exhaust, which has a substrate and a catalyst coating layer formed on the substrate, wherein the catalyst coating layer comprises a ceria-zirconia-based composite oxide having a pyrochlore structure in an amount of 5 to 100 g/L based on the volume of the substrate, the ceria-zirconia-based composite oxide has a secondary particle size (D50) of 3 &#x3bc;m to 7 &#x3bc;m, and the ceria-zirconia-based composite oxide optionally contains praseodymium.

Catalyst for purifying exhaust gas

A ceria-zirconia-based composite oxide including a composite oxide containing ceria and zirconia, wherein the ceria-zirconia-based composite oxide contains at least one member selected from the group consisting of praseodymium, lanthanum, and yttrium in an amount of 0.5 to 5.0 mol % relative to a total amount of the cations contained in the ceria-zirconia-based composite oxide, where the ratio of the content of both cerium and the at least one member selected from the group consisting of praseodymium, lanthanum, and yttrium in the ceria-zirconia-based composite oxide to the content of zirconium therein ([cerium and the at least one member selected from the group consisting of praseodymium, lanthanum, and yttrium]:[zirconium]) is in the range of 43:57 to 48:52 by mole ratio.

Ceria-zirconia-based composite oxide and method for producing same, and catalyst for exhaust gas purification including ceria-zirconia-based composite oxide

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Kakegawa, Japan

Kosuke Iizuka