An exhaust gas-purifying catalyst of the present invention comprises a substrate, and one or more catalytic layers provided on the substrate, wherein at least one of the catalytic layers (i) contains a precious metal, alumina, and an acidic oxide element, (ii) has a correlation coefficient ρ.sub.Al,AE of 0.70 or more, and (iii) has a correlation coefficient ρ.sub.PM,AE of 0.70 or more.

A catalysed filter for a positive ignition internal combustion engine comprises a porous filtering substrate having a total substrate length coated with a three-way catalyst washcoat composition comprising at least one precious metal selected from the group consisting of rhodium and one or both of platinum and palladium supported on a high surface area oxide, and an oxygen storage component, which composition being axially shared by a first zone comprising inlet surfaces of a first substrate length<total substrate length and a second zone comprising outlet surfaces of a second substrate length<total substrate length, wherein a sum of the substrate length in the first zone and the substrate length in the second zone≧100% and wherein one or both of the following applies: a washcoat loading in the first zone>second zone; and a total precious metal loading in the first zone>second zone.

The present invention relates to a method for producing a multilayer catalyst, to the multilayer catalyst produced by the method, and to the use of the catalyst for after-treatment of exhaust gases.

Provided is a powder inorganic oxide containing Al, Ce and Zr as constituent elements, that affords a molded product with a density of 1.0 to 1.3 g/ml by placing 4.0 g of the inorganic oxide in a cylindrical container having diameter 20 mm and performing uniaxial molding under conditions of room temperature and pressure of 29.4 MPa for 30 sec., and achieves an average shrinkage percentage of not more than 14.0% as calculated by the following formula: average shrinkage percentage (%)=100×{(1−(c)/(a))+(1−(d)/(b))}/2 wherein each symbol is as defined in the DESCRIPTION.

Catalyst compositions, articles, systems and methods related to a three-way-catalyst composition comprising alumina doped with a transition metal.

[Summary]

[Problem]

The problem addressed by the present invention lies in providing an exhaust gas purification filter which can efficiently treat particulate matter in exhaust gas.

[Solution]

The present invention provides an exhaust gas purification filter including a substrate comprising a plurality of porous partitions, wherein the partitions form an exhaust gas flow path, a porous catalytic layer is provided on the partitions and the catalytic layer having a thickness of 10 μm or greater is provided over at least 20% of the total length of the partitions in the lengthwise direction thereof, and the catalytic layer having a thickness of 10 μm or greater is not present on the partitions 15 mm from an outflow side.

A core-shell oxide material comprises: a core which comprises a ceria-zirconia based solid solution powder having at least one ordered phase of a pyrochlore phase and a κ phase; and a shell which comprises an alumina based oxide disposed on at least a portion of a surface of the core.

A layered catalyst composite for the treatment of exhaust gas emissions, effective to provide lean NO.sub.x trap functionality and three-way conversion functionality is described. Layered catalyst composites can comprise catalytic material on a substrate, the catalytic material comprising at least two layers. The first layer comprising rare earth oxide-high surface area refractory metal oxide particles, an alkaline earth metal supported on the rare earth oxide-high surface area refractory metal oxide particles, and at least one first platinum group metal component supported on the rare earth oxide-high surface area refractory metal oxide particles. The second layer comprising a second platinum group metal component supported on a first oxygen storage component (OSC) and/or a first refractory metal oxide support and, optionally, a third platinum group metal supported on a second refractory metal oxide support or a second oxygen storage component.

An exhaust gas-purifying catalyst material includes first oxide particles having an average particle diameter D.sub.av of 1 μm to 95 μm and having an oxygen storage capacity, second oxide particles having an average particle diameter D.sub.av of 0.05 μm to 0.5 μm, containing a metal element, and having no oxygen storage capacity, precious metal particles, and acidic oxide particles. The material has a correlation coefficient ρ of 0.45 or more obtained using first characteristic X-ray intensity for the metal element contained in the second oxide particle, second characteristic X-ray intensity for an element other than oxygen contained in the acidic oxide particle, and third characteristic X-ray intensity for a precious metal element contained in the precious metal particle.

To reduce an OSC material, while maintaining necessary OSC capacity; and to improve heat resistance and reactivity of a precious metal. Proposed is an exhaust gas purifying catalyst which comprises a first catalyst layer that is formed on the surface of a substrate that is formed of a ceramic or a metal, and a second catalyst layer that is formed on the upper side of the first catalyst layer. The first catalyst layer comprises a precious metal, an OSC material and an alumina, and the OSC material and the alumina are comprised at a mass ratio of OSC material:alumina=1:7 to 1:3. The second catalyst layer comprises a precious metal, an OSC material and an alumina, and the OSC material and the alumina are comprised at a mass ratio of OSC material:alumina=1:1 to 10:0.