Provided is a catalyst article for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The catalyst article has a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia.

A mixed oxide, a catalytic composition, a catalytic wall-flow monolith, the use of the mixed oxide and the process of the preparation of the mixed oxide. The mixed oxide comprises zirconium, cerium, lanthanum and optionally at least one rare earth element other than cerium and other than lanthanum. The catalytic composition and the wall-flow monolith comprise the particles of the mixed oxide. The use of the mixed oxide is in the preparation of a coating on a filter. The process of preparation of the mixed oxide consists jet milling. The mixed oxide is a compromise between a calibrated size and a low viscosity when in the form of an aqueous slurry while retaining a high specific surface area and a high pore volume.

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 m to 95 m and having an oxygen storage capacity, second oxide particles having an average particle diameter D.sub.av of 0.05 m to 0.5 m, containing a metal element, and having no oxygen storage capacity, precious metal particles, and acidic oxide particles. The material has a correlation coefficient 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.

A CO slip catalyst, for treating an exhaust gas from a lean burn internal combustion engine, is disclosed. The CO slip catalyst comprises palladium and a ceria-containing material. The invention also includes a method for oxidizing excess CO in an exhaust gas, wherein the excess CO results from the periodic contact of an upstream catalyst under rich exhaust conditions. The method comprises contacting the excess CO in the exhaust gas with a CO slip catalyst at a temperature in the range of 100 to 700 C.

A catalysed substrate monolith 12 for use in treating exhaust gas emitted from a lean-burn internal combustion engine, which catalysed substrate monolith 12 comprising a first washcoat coating 16 and a second washcoat coating 18, wherein the first washcoat coating comprises a catalyst composition comprising at least one platinum group metal (PGM) and at least one support material for the at least one PGM, wherein at least one PGM in the first washcoat coating is liable to volatilise when the first washcoat coating is exposed to relatively extreme conditions including relatively high temperatures, wherein the second washcoat coating comprises at least one metal oxide for trapping volatilised PGM and wherein the second washcoat coating is oriented to contact exhaust gas that has contacted the first washcoat coating.

Catalytic cores for a wall-flow filter include juxtaposed channels extending longitudinally between an inlet side and an outlet side of the core, wherein the inlet channels are plugged at the outlet side and outlet channels are plugged at the inlet side. Longitudinal walls forming the inlet and outlet channels separate the inlet channels from the outlet channels. The walls include pores that create passages extending across a width of the walls from the inlet channels to the outlet channels. Catalysts are distributed across the width and length of the walls within internal surfaces of the pores in a manner such that the loading of each catalyst across the width varies by less than 50% from an average loading across the width.

Provided is a catalyst article for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The catalyst article has a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia.

This disclosure features an exhaust aftertreatment system that includes a selective catalytic reduction catalyst that includes (1) a metal oxide catalyst and a metal zeolite catalyst, (2) a metal oxide catalyst that is other than a vanadium oxide catalyst and a vanadium oxide catalyst, or (3) a metal oxide catalyst that is other than a vanadium oxide catalyst together with a metal zeolite catalyst and a vanadium oxide catalyst. When used in a selective catalytic reduction system in a diesel engine, the catalyst composition can increase a conversion efficiency of nitrogen oxides (NOx) to nitrogen and water by a minimum of 2 percent compared to the metal zeolite catalyst alone, the metal oxide catalyst alone, or the vanadium oxide catalyst alone, when present.

A satisfactory oxygen storage material and a method for producing it are provided. The oxygen storage material comprises zirconia particles with a ceria-zirconia complex oxide supported on the zirconia particles. The ceria-zirconia complex oxide includes a pyrochlore phase and has a mean crystallite diameter of 10 nm to 22.9 nm.