Provided is an exhaust gas purification catalyst having a catalyst performance and an OSC performance in a compatible manner in an air-fuel ratio (A/F) rich atmosphere where HC poisoning is likely to occur. The exhaust gas purification catalyst includes a substrate and a catalyst coating layer coated on the substrate. The catalyst coating layer includes a first catalyst coating layer containing Pd and/or Pt as a catalyst metal and a second catalyst coating layer containing Rh as a catalyst metal. The first catalyst coating layer is formed from an end portion in an upstream side with respect to an exhaust gas flow direction in the exhaust gas purification catalyst. The second catalyst coating layer includes a high specific surface area OSC material having a specific surface area of more than 40 m.sup.2/g, a medium specific surface area OSC material having a specific surface area of 4 m.sup.2/g to 40 m.sup.2/g, and a low specific surface area OSC material having a specific surface area of less than 4 m.sup.2/g.

The present invention relates to a particulate filter which comprises a wall-flow filter of length L and two different catalytically active coatings Y and Z, wherein the wall-flow filter comprises channels E and A that extend in parallel between a first and a second end of the wall-flow filter and are separated by porous walls which form the surfaces O.sub.E and O.sub.A, respectively, and wherein the channels E are closed at the second end and the channels A are closed at the first end, and wherein the coatings Y and Z have the same oxygen storage components and the same carrier materials for noble metals. The invention is characterized in that the coating Y is located in the channels E on the surfaces O.sub.E and the coating Z is located in the channels A on the surfaces O.sub.A.

The invention relates to a particulate filter for removing particles, carbon monoxide, hydrocarbons and nitrogen oxides out of the exhaust gas of combustion engines operated with stoichiometric air/fuel mixture, comprising a wall flow filter with length L and a coating Z, wherein the wall flow filter includes channels E and A which extend in parallel between a first and a second end of the wall flow filter and are separated by porous walls, which form surfaces OE or OA, and wherein the channels E are closed at the second end and the channels A are closed at the first end, characterised in that coating Z is located in the porous walls and extends from the first end of the wall flow filter over the entire length L, and includes active aluminum oxide, two different cerium/zirconium/rare earth metal mixed oxides and at least one platinum group metal.

The present invention relates to a particulate filter which comprises a wall-flow filter of length L and two different catalytically active coatings Y and Z, wherein the wall flow filter comprises channels E and A that extend in parallel between a first and a second end of the wall-flow filter and are separated by porous walls which form the surfaces O.sub.E and O.sub.A, respectively, and wherein the channels E are closed at the second end and the channels A are closed at the first end. The invention is characterized in that the coating Y is located in the channels E on the surfaces O.sub.E and the coating Z is located in the porous walls.

The invention relates to a catalytic converter for removing carbon monoxide, hydrocarbons and nitrogen oxides from the exhaust gas of internal combustion engines operated with stoichiometric air-fuel mixture, which catalytic converter comprises a substrate of the length L and a catalytic coating, characterized in that the coating is located on the walls of the substrate and extends, proceeding from one end of the substrate, over a length corresponding to at least 50% of L and comprises active aluminum oxide, two cerium/zirconium/rare-earth-metal mixed oxides different from each other, and at least one platinum group metal.

An exhaust gas purification catalyst including particles of a catalyst metal supported on secondary particles of an inorganic oxide, wherein when scanning transmission electron microscope-energy dispersive X-ray line analysis is performed from a surface of the secondary particles toward a center thereof, a support density of the catalyst metal on a surface side of the secondary particles is greater than the support density of the catalyst metal in a center part of the secondary particles.

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.

An exhaust gas cleaning catalyst that has: a substrate having a wall flow structure, wherein an entry side cell, in which the end part on an exhaust gas inflow side is open, and an exit side cell, in which the end part on the exhaust gas outflow side is open, are divided by a porous dividing wall; and a first catalyst layer that includes a metal catalyst and is disposed within the dividing wall so as to be in contact with the exit side cell and not in contact with the entry side cell, and no catalyst layer is provided in the region in contact with the entry side cell.

Described are catalysts effective to abate NO.sub.x, hydrocarbons, and carbon monoxide from a gasoline engine exhaust gas. Such catalysts include a substrate having a first and second material disposed thereon, the first material effective to catalyze selective catalytic reduction of nitrogen oxides in the presence of ammonia and the second material effective to abate hydrocarbons and carbon monoxide, the first material comprising a molecular sieve promoted with copper and/or iron in a low loading, the second material comprising at least one oxide of Ni, Fe, Mn, Co, and Cu on a support selected from oxides of Ce, CeZr, Zr, Mn, Pr and combinations thereof. Also described are gasoline engine exhaust gas treatment systems and methods of treating exhaust gas from a gasoline engine.

Provided is an inorganic oxide containing Al, Ce and Zr as constituent elements and having a ratio of emission intensity I.sub.A at 420 nm and emission intensity I.sub.B at 470 nm (I.sub.B/I.sub.A) of not more than 1.65 in an emission spectrum obtained when a light at wavelength 200 nm is irradiated.