Daihatsu Motor Company, Ltd.

Cataler Corporation

Hokko Chemical Industry Co., Ltd.

Toyota Jidosha Kabushiki Kaisha

Ngk Spark Plug Company, Limited

Mari Uenishi

Hirohisa Tanaka

Isao Tan

Masashi Taniguchi

Keiichi Narita

Mareo Kimura

Satoshi Matsueda

Akimasa Hirai

Noboru Sato

Naoto Miyoshi

Takeru Yoshida

Norihiko Nadanami

Nobuhiko Kajita

Yasunori Sato

Takaaki Kanazawa

Kazunobu Ishibashi

Akiya Chiba

Kimiyoshi Kaneko

Yoshinori Ishii

Senshu Mitachi

Shigehito Sakai

Ryouhei Iwasaki

An excellent oxygen storage capacity is achieved even in the case used for a long period of time under high temperature conditions. An oxygen storage material contains a first particle made of a composite oxide of cerium and zirconium or a composite oxide of cerium, a rare-earth element other than cerium and zirconium, a second particle including a composite oxide of a rare-earth element, an alkaline-earth element and zirconium, and a precious metal. A part of the precious metal forms a solid solution with the composite oxide included in the second particle.

Oxygen storage material

An exhaust gas-purifying catalyst () contains a rare-earth element, an alkaline-earth element, zirconium and a precious metal, wherein an atomic ratio of the alkaline-earth element with respect to a sum of the rare-earth element and the zirconium is 10 atomic % or more, a part of the rare-earth element and a part of zirconium form a composite oxide with at least a part of the alkaline-earth element, and the composite oxide and a part of the precious metal form a solid solution.

Exhaust gas-purifying catalyst

An object of the present invention is to provide an exhaust gas-purifying catalyst that is less prone to cause a decrease in its activity even when used at high temperatures in an atmosphere whose oxygen concentration is high. An exhaust gas-purifying catalyst of the present invention includes a composite oxide of alkaline-earth metal and aluminum, and platinum, wherein at least a part of the composite oxide and at least a part of the platinum forms a solid solution.

Exhaust gas-purifying catalyst and method of manufacturing the same

Provided is a catalyst with a noble metal efficiently supported on the surfacemost thereof. A composite oxide-containing layer is formed on a catalyst carrier so as to contain a perovskite-type composite oxide represented by the following general formula (1) and an other composite oxide, and a noble metal layer is further formed on the catalyst carrier so as to be supported on the surfacemost of the catalyst carrier by immersing the catalyst carrier formed with the composite oxide-containing layer in an aqueous noble metal salt solution to impregnate the catalyst carrier with the aqueous noble metal salt solution:ABO&#x2003;&#x2003;(1)(wherein A represents at least one element selected from rare earth elements and alkaline earth metals; B represents at least one element selected from transition elements (excluding rare earth elements); x represents an atomic ratio of less than 1; y represents an atomic ratio of 1.0; and &#x3b4; represents an oxygen excess or an oxygen deficiency.)

Catalyst

To provide a heat-resistant oxide which is excellent in heat resistance and durability at high temperature and has high activity, a heat-resistant oxide which has an oxide crystal structure and in which a rate of a solid solution of a noble metal in the oxide crystal structure is 50% or more is obtained by heat-treating (secondarily baking) a precursor composition comprising zirconia, at least one coordinative element selected from the group consisting of rare earth elements, alkaline earth elements, aluminum and silicon, and at least one noble metal selected from the group consisting of platinum, rhodium and palladium at 650&#xb0; C. or higher.

Heat-resistant oxide

To provide a method for industrially efficiently producing an exhaust gas purifying catalyst containing a perovskite-type composite oxide which is stable and has a less reduced specific surface area and is also effectively prevented from decreasing in its catalytic performance even in endurance in high temperature oxidative reducing atmospheres, a pre-crystallization composition containing elementary components constituting a perovskite-type composite oxide containing a noble metal is prepared, is mixed with a powder of theta-alumina and/or alpha-alumina to prepare a mixture, and the mixture is heat treated. Thus, the resulting perovskite-type composite oxide supported by the powder of theta-alumina and/or alpha-alumina can keep its thermostability at a sufficient level thereby to effectively prevent the catalytic performance from decreasing. This method can industrially efficiently produce the exhaust gas purifying catalyst.

Method for producing exhaust gas purifying catalyst

To provide a perovskite-type composite oxide which has stable quality in which a solid solution of Pd is formed at a high rate, a method for producing the perovskite-type composite oxide, and a catalyst composition containing the perovskite-type composite oxide, the perovskite-type composite oxide is produced by formulating materials in accordance with each atomic ratio of a perovskite-type composite oxide represented by the following general formula (1):ABPdO&#x2003;&#x2003;(1)wherein A represents at least one element selected from rare earth elements and alkaline earth metals; B represents at least one element selected from transition elements (excluding rare earth elements, and Pd), Al and Si; x represents an atomic ratio satisfying the following condition: 1&#x3c;x; y represents an atomic ratio satisfying the following condition: 0&#x3c;y&#x2266;0.5; and &#x3b4; represents an oxygen excess.

Perovskite-type composite oxide, catalyst composition and method for producing perovskite-type composite oxide

A catalyst composition which prevents deterioration due to grain growth of Rh and/or Pt, includes a perovskite-type composite oxide represented by the following general formula (1):AA'BB&#x2032;NO&#x2003;&#x2003;(1)wherein A represents at least one element selected from alkaline earth metals; A&#x2032; represents at least one element selected from rare earth elements; B represents at least one element selected from Ti, Zr, and Hf; B&#x2032; represents at least one element selected from transition elements (excluding rare earth elements, Ti, Zr, Hf, Rh, and Pt) and Al; N represents at least one element selected from Rh and Pt; x represents an atomic ratio satisfying the following condition: 0&#x2266;x&#x2266;0.4; y represents an atomic ratio satisfying the following condition: 0&#x2266;y&#x3c;0.5; z represents an atomic ratio satisfying the following condition: 0&#x3c;z&#x2266;0.5; and X represents 0 when N represents Pt alone.

Catalyst composition

To provide an exhaust gas purifying catalyst which can maintain the catalytic activity at a high level over a long time and can achieve satisfactory emission control performance, an exhaust gas purifying catalyst is prepared so as to contain a noble metal, a perovskite-type composite oxide represented by the following general formula (3), and theta-alumina and/or alpha-alumina:ABNO&#x2003;&#x2003;(3)wherein A represents at least one element selected from rare-earth elements and alkaline earth metals; B represents at least one element selected from Al and transition elements excluding rare-earth elements and noble metals; N represents a noble metal; and m represents an atomic ratio of N satisfying the following relation: 0&#x3c;m&#x3c;0.5.

Catalyst for clarifying exhaust gas

An exhaust gas purifying catalyst that provides the excellent low-temperature activity and also develops the good catalytic activity of rhodium to produce a good purifying performance economically. The exhaust gas purifying catalyst comprises an alumina on which rhodium and platinum are previously supported; a zirconium complex oxide on which rhodium and platinum are previously supported; and a cerium complex oxide on which platinum is previously supported.

Exhaust gas purifying catalyst

A catalytic converter for cleaning exhaust gas includes a heat-resistant support, and a catalytic coating formed on the heat-resistant support. The catalytic coating contains zirconium complex oxide on which Pt and Rh are coexistently carried, and cerium complex oxide on which Pt and Rh are coexistently carried. The Pt- and Rh-carrying zirconium complex oxide and the Pt- and Rh-carrying cerium complex oxide are contained in a same layer of the catalytic coating.

Catalytic converter for cleaning exhaust gas

To provide an exhaust gas purifying catalyst that requires a smallest possible quantity of rhodium for developing the activity effectively, so as to produce an excellent purifying performance economically, a zirconium complex oxide on which rhodium and platinum are previously supported, and a cerium complex oxide on which platinum and/or palladium are previously supported are contained in an exhaust gas purifying catalyst.

A catalytic converter for cleaning exhaust gas includes a first coating layer formed on a heat-resistant support, and a second coating layer formed on the first coating layer. The first coating layer contains alumina which supports palladium. The second coating layer contains Ce&mdash;Zr complex oxide which coexistently carries platinum and rhodium, and Zr&mdash;Ce complex oxide which differs in composition from the Ce&mdash;Zr complex oxide and which coexistently carries platinum and rhodium.

To provide an exhaust gas purifying catalyst that can develop good catalytic activity even in high-temperature endurance and also produce excellent low-temperature property, a coating layer having an outside layer and an inside layer is formed on a catalyst carrier, the outside layer being made to contain a noble metal previously supported on a heat-resisting oxide and a cerium complex oxide, and the inside layer being made to contain a heat-resisting oxide on which no noble metal is supported.

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Shiga, Japan

Mari Uenishi