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 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: 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: An exhaust gas-purifying catalyst includes a zeolite and a perovskite composite oxide containing palladium placed at its B site.

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 zeolite and a perovskite composite oxide containing palladium placed at its B site.

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.