Abstract: The composite oxide and the composite oxide carrier are manufactured by the precursor forming step and firing step. The composite oxide catalyst is obtained by preparing a composite of catalytic components simultaneously with the formation of the precursor of composite oxide in the step of forming the precursor of composite oxide. The composite oxide and the composite oxide carrier are composed of a composite oxide in which at least one of cerium and zirconium, and aluminium disperse with extremely high homogeneity. With this structure, the heat resistance of the carrier is improved and consequently, enlargement of particles of the composite oxide defining the carrier, and sintering of adjacent particles of the composite oxide can be restrained, whereby the catalyst using the composite oxide carrier in accordance with the present invention is excellent in heat resistance.

Abstract: The composite oxide and the composite oxide carrier are manufactured by the precursor forming step and firing step. The precursor forming step includes high speed mixing means. The composite oxide catalyst is obtained by preparing a composite of catalytic components simultaneously with the formation of the precursor of composite oxide in the step of forming the precursor of composite oxide. The composite oxide and the composite oxide carrier are composed of a composite oxide in which at least one of cerium and zirconium, and aluminium disperse with extremely high homogeneity. With this structure, the heat resistance of the carrier is improved and consequently, enlargement of particles of the composite oxide defining the carrier, and sintering of adjacent particles of the composite oxide can be restrained, whereby the catalyst using the composite oxide carrier in accordance with the present invention is excellent in heat resistance.

Abstract: A solid solution particle of oxides contains a solid solution of oxides in which one oxide is dissolved into the other oxide, and in which the degree of dissolution of one oxide into the other oxide is not less 50%, and in which an average diameter of crystallite is not more than 100 nm. The solid solution particle of oxides has small average diameter of a crystallite and large specific surface area, and it improves capacities such as an oxygen storage ability due to high degree of dissolution. A catalyst for purifying exhaust gases has excellent purifying performance by employing the solid solution comprising ceria and zirconia which has large OSC and high oxygen adsorption and discharge speed.

Abstract: A catalyst for purifying exhaust gases includes a porous support; a cerium oxide or a solid solution of a cerium oxide and a zirconium oxide in a state of mutual solid solution, loaded on the porous support; and a noble metal element loaded on the porous support. The cerium oxide or the solid solution has an average particle diameter of from 5 to 100 nm. The cerium oxide is present in the solid solution in an amount of from 0.2 to 4.0 by molar ratio with respect to the zirconium oxide therein. The catalyst can be prepared by: coating and calcinating on a support substrate a slurry of a cerium oxide sol, a cerium oxide sol and a zirconium oxide sol, on a solid solution powder of a cerium oxide and a zirconium oxide in a state of mutual solid solution; and loading a noble metal element thereon.

Abstract: Disclosed is a method for producing oxide powders and complex oxide powders having an oxygen amount smaller than the stoichiometric amount. The method comprises: spraying a combustible liquid that contains at least one raw material of metals capable of having a plural number of valences and compounds of such metals; and firing the raw material to give a powder of an oxide of at least one of said metals. The oxygen amount in the atmosphere in which the combustible liquid containing said raw material is sprayed and fired is smaller than the total of the oxygen amount necessary for the complete combustion of said combustible liquid and the oxygen amount necessary for the conversion of said raw material into an oxide that is the most stable in air at room temperature.

Abstract: An internal combustion engine in which a three-way catalyst (12) for purification of the exhaust gas is arranged in the exhaust passage, wherein the relationship between the magnitude of the stress causing deterioration of the three-way catalyst (12), for example the catalytic bed temperature, and the rate of deterioration of the performance of the catalyst is found. A durability test is performed by raising the catalytic bed temperature higher than that of the vehicle under market driving. The length of the durability test at this time is determined from the relationship between the catalytic bed temperature and the rate of deterioration of the performance of the catalyst so as to give the same degree of deterioration of the performance of the catalyst as with market driving. The length of the durability test required for giving the same degree of deterioration of the performance of the catalyst is much shorter than the market driving time.

Abstract: A process for producing a powder of composite oxide which includes cerium and zirconium, or which includes cerium, zirconium and further a rare-earth element other cerium. The process includes: dissolving nitrate, sulfate and/or acetate of constituent elements of the composite oxide into water in a predetermined ratio; and spraying and heating a resulting aqueous solution to oxidize the constituent elements of the composite oxide for converting them into a powder of a composite oxide. The thus produced composite oxide powder is micro-fine, homogeneous, and heat resistant.

Abstract: A device for evaluating catalyst performance deterioration includes an air-fuel ratio sensor and a temperature sensor. The degree of catalyst performance deterioration per unit time is calculated based on the concentration of oxygen in the exhaust gas and the temperature of the catalyst. The deterioration of the catalyst is evaluated on the basis of the accumulated value of the degree of catalyst performance deterioration per unit time.

Abstract: A method for producing a catalyst having high catalytic activity even at high temperatures of 1200.degree. C. or higher. Fine alumina particles, of which 50% by weight or more have a particle size of 100 nm or less, are mixed with a catalytic component and a substance of inhibiting the sintering of fine alumina particles to form a slurry mixture. This slurry is dried and then calcined to obtain a porous catalyst. The fine alumina particles in the porous catalyst have a large specific surface area even at high temperatures and therefore the porous catalyst maintains its high catalytic activity even at high temperatures of 1200.degree. C. or higher.

Abstract: An exhaust gas purifying catalyst for oxidizing HC and CO and for reducing NOx is provided, which comprises at least one oxide of rare earth element, rhodium, and at least one of platinum and palladium loaded on alumina grains. The major amount of rhodium is dispersed on the oxide of rare earth element. Thus, the rhodium solidification into the alumina grains is prevented. Further, when cerium oxide accompanying lanthanum oxide, neodymium oxide or a mixture thereof is used as the oxide of rare earth element, the sintering of cerium oxide or palladium at a high temperature is suppressed since it forms a complex oxide with lanthanum oxide, neodymium oxide or a mixture thereof. Additionally, when stabilized alumina grains in which a rare earth element and an alkali earth element are present in a solid solution state are used, the deterioration of NOx purifying activity of the catalyst at a high temperature is suppressed.

Abstract: Exhaust gas purifying method and apparatus for internal combustion engines in which the temperature of an exhaust gas purifying catalyst is detected and, as desired, oxygen content of exhaust gas is further detected, and in which the actual air-fuel ratio is varied toward the higher air-fuel ratio side and the lower air-fuel ratio side with respect to the theoretical air-fuel ratio, in accordance with the frequency and amplitude preset dependent on the kind of the catalyst and set based on these measured values.

Abstract: A catalyst for the steam reforming of hydrocarbons into gases such as methane, hydrogen and carbon monoxide and a method of preparing the same. The catalyst which comprises cerium oxide and rhodium supported on a carrier can maintain high catalytic activity and durability for steam reforming without any carbon deposition on its surface.

Abstract: A catalyst for reducing nitrogen oxides, carbon monoxide and hydrocarbons, the noxious components in exhaust gases from internal combustion engines, etc., which comprises: a carrier having a substructure of refractory material in the form of a honeycomb structure, etc., and a porous layer of a powder formed on the surface thereof selected from the group consisting of a powder of zirconium oxide and a mixed powder of zirconium oxide powder with at least one powder selected from the group consisting of alumina, alumina-magnesia spinel and cerium oxide; and a catalyst ingredient supported thereon consisting of cerium oxide and a metal selected from the group consisting of platinum, palladium and mixtures thereof.

Abstract: A catalyst for reducing nitrogen oxides, carbon monoxide and hydrocarbons, the noxious components in exhaust gases from internal combustion engines, etc., comprising: a porous carrier of ceramic selected from the group consisting of alumina and alumina-magnesia spinel; and a catalyst ingredient supported thereon consisting essentially of zirconium oxide, cerium oxide and a metal selected from the group consisting of platinum, palladium and mixtures thereof.

Abstract: A catalyst for reducing nitrogen oxides, carbon monoxide and hydrocarbons, the noxious components in exhaust gases from internal combustion engines, etc., comprising: a porous carrier consisting essentially of zirconia and at least one oxide selected from the group consisting of cerium oxide, manganese oxide and iron oxide; and a metal as a catalyst ingredient supported thereon selected from the group consisting of platinum, palladium and mixtures thereof.A method for producing the aforesaid catalyst.