Abstract: An exhaust gas-purifying catalyst is less prone to cause a decrease in its activity even when used in a high temperature atmosphere containing oxygen at a high concentration. The exhaust gas-purifying catalyst includes a composite oxide and Pd or a second solid solution of a composite and Rh and/or Pt. The first and second solid solutions have perovskite structure and are represented by ABO3 and CDO3, respectively. The composite oxide catalyst is supported by a composite oxide support including a composite oxide of spinel structure represented by EF2O4 or a composite oxide represented by GAl12O19. A and B represent a rare-earth element and a transition element, respectively. C and G represent an alkaline-earth element. D represents one or more of Ti, Zr, Hf and Ce. E represents an alkaline-earth element and/or a transition element. F represents one or more of Al, Mg and transition elements.

Abstract: To provide a catalyst composition containing a novel perovskite-type composite oxide which permits reversible entrance and exit of noble metals, a catalyst composition is prepared so as to contain a perovskite-type composite oxide represented by the general formula (1): AxA?wByB?(1-y-z)NzO3±???(1) (wherein A represents at least one element selected from alkaline earth metals; A? represents at least one element selected from rare earth elements; B represents a tetravalent rare earth element; B? represents at least one element selected from transition elements (excluding tetravalent rare earth elements, Rh, Pd and Pt); N represents at least one element selected from Rh, Pd and Pt; x and w represent an atomic ratio satisfying the following relations: 0.8?x+w?1.3 (0.8?x?1.3, 0?w?0.4); y represents an atomic ratio satisfying the following relation: 0<y<1.0; z represents an atomic ratio satisfying the following relation: 0<z?0.5; and ? represents an oxygen excess or deficiency amount).

Abstract: An exhaust gas-purifying catalyst (1) 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.

Abstract: An object of the present invention is to provide a catalyst composition containing a perovskite-type composite oxide which exhibits a satisfactory catalytic performance over a long time even in a high temperature atmosphere and has a stable quality in which Rh and/or Pt dissolves to form a solid solution at a high rate. To achieve the object described above, in the present invention the catalyst composition is prepared to comprise an Rh-containing perovskite-type composite oxide represented by the following general formula (I) and/or a Pt-containing perovskite-type composite oxide represented by the following general formula (II) and a thermostable oxide optionally containing a noble metal.

Abstract: 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° C. or higher.

Abstract: An object of the present invention is to provide a method for producing a noble metal-containing heat-resistant oxide having excellent durability under a high temperature atmosphere According to the method for producing a noble metal-containing heat-resistant oxide of the present invention, a coordination element material containing coordination elements is blended and the obtained first precursor composition is subjected to a first heat treatment to form a first heat-treated composition (crystal lattice) such as a perovskite-type composite oxide or a fluorite-type composite oxide. Then, a noble metal element material containing a noble metal element such as Pt, Rh or Pd is blended with the first heat-treated composition and the secondary precursor composition thus obtained is subjected to a second heat treatment (baking) at a temperature which is higher than that of the first heat treatment and is 600° C. or higher.

Abstract: An exhaust gas-purifying catalyst includes a carrier, and an active component formed of a noble metal, carried by the carrier. The carrier has a core portion comprising a cubic or tetragonal stabilized zirconia-based composite oxide containing at least one stabilizing element, and a surface layer portion including a heat resistant zirconia-based composite oxide formed on a surface of the core portion. The surface layer has a specific surface area which is larger than a specific surface area of the core portion. A part of the noble metal is solid-solutioned into the zirconia-based composite oxide of the surface layer portion, and the balance of the noble metal is carried on a surface of the surface layer portion.

Abstract: 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): A1?xA?xB1?(y+z)B?yNzO3??(1) wherein A represents at least one element selected from alkaline earth metals; A? represents at least one element selected from rare earth elements; B represents at least one element selected from Ti, Zr, and Hf; B? 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?x?0.4; y represents an atomic ratio satisfying the following condition: 0?y<0.5; z represents an atomic ratio satisfying the following condition: 0<z?0.5; and X represents 0 when N represents Pt alone.

Abstract: 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): AxB(1-y)PdyO3+???(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<x; y represents an atomic ratio satisfying the following condition: 0<y?0.5; and ? represents an oxygen excess.

Abstract: 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: AB1-mNmO3??(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<m<0.5.

Abstract: An exhaust gas-purifying catalyst includes a carrier, and an active component formed of a noble metal, carried by the carrier. The carrier has a core portion comprising a cubic or tetragonal stabilized zirconia-based composite oxide containing at least one stabilizing element, and a surface layer portion including a heat resistant zirconia-based composite oxide formed on a surface of the core portion. The surface layer has a specific surface area which is larger than a specific surface area of the core portion. A part of the noble metal is solid-solutioned into the zirconia-based composite oxide of the surface layer portion, and the balance of the noble metal is carried on a surface of the surface layer portion.

Abstract: 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.

Abstract: 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: AB1?mNmO3??(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<m<0.5.

Abstract: 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.

Abstract: To provide an exhaust gas purifying catalyst which can maintain the catalytic activity of Pt 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 composite oxide having a perovskite structure represented by the general formula (1): A1-xA?xB1-y-zB?yPtzO3??(1) wherein A represents at least one element selected from rare-earth elements and essentially including one or more rare-earth elements each having a valence of 3 as the only valence; A? represents at least one element selected from alkaline earth metals and Ag; B represents at least one element selected from Fe, Mn, and Al; B? represents at least one element selected from transition elements excluding Pt, Fe, Mn, Co, and the rare-earth elements; and x, y, and z are atomic ratios satisfying the following relations: 0<x?0.5, 0?y<0.5, and 0<z?0.5.

Abstract: To provide an exhaust gas purifying catalyst which can maintain the catalytic activity of Rh 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 composite oxide having a perovskite structure represented by the general formula (1): ABRhO3??(1) wherein A represents at least one element selected from rare-earth elements essentially including one or more rare-earth elements each having a valence of 3 as the only valence and arbitrarily including Ce and/or Pr; and B represents at least one element selected from transition elements excluding Co, Rh and the rare-earth elements, and Al.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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—Zr complex oxide which coexistently carries platinum and rhodium, and Zr—Ce complex oxide which differs in composition from the Ce—Zr complex oxide and which coexistently carries platinum and rhodium.