The exhaust gas cleaning catalyst according is provided with a substrate and a catalyst coat layer formed on a surface of the substrate. The catalyst coat layer is formed as a laminate structure having an upper layer and a lower layer. The upper layer is a Pd-free layer that does not contain Pd, and the lower layer is a Pd-containing layer. In addition, when a region of the lower layer that corresponds to 20% of the length of the exhaust gas cleaning catalyst from the exhaust gas inlet side end towards the exhaust gas outlet side of the exhaust gas cleaning catalyst is divided into four equal regions to be each 5% of the length, the relationship A>B>C is satisfied, where A, B, and C represents the Pd content in the first, second, and third region respectively.

This invention relates to an aqueous dispersion of particles, the dispersion having a particle content of 10-70 wt %, and the particles comprising, on an oxide basis: (a) 10-98 wt % in total of ZrO.sub.2+HfO.sub.2, and (b) 2-90 wt % in total of AI.sub.2O.sub.3, CeO.sub.2, La.sub.2O.sub.3, Nd.sub.2O.sub.3, Pr.sub.6O.sub.11, Y.sub.2O.sub.3, or a transition metal oxide, wherein the dispersion has a Z-average particle size of 100-350 nm and the particles have a crystallite size of 1-9 nm. The invention also relates to a substrate coated with the aqueous dispersion of particles.

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 is provided which can be more enhanced in NOx purification performance. An exhaust gas purification catalyst including a substrate, a NOx storage layer located over the substrate, an oxidation catalyst layer located over a part of the NOx storage layer, the part being located upstream in an exhaust gas flow direction, and a reduction catalyst layer located over a part of the NOx storage layer, the part being located downstream in an exhaust gas flow direction, wherein the NOx storage layer includes an oxidation catalyst including Pd or Pd and Pt, and a NOx storage material including at least one element selected from the group consisting of an alkali metal, an alkali earth metal and a rare-earth element, the oxidation catalyst layer includes an oxidation catalyst including Pt or Pt and Pd, the reduction catalyst layer includes a reduction catalyst including Rh, and a total content rate (mol %) of Pt and Pd based on a total content rate (100 mol %) of metal element(s) in the oxidation catalyst layer is higher than a total content rate (mol %) of Pt and Pd based on a total content rate (100 mol %) of metal elements in the NOx storage layer.

The present invention relates to a honeycomb catalytic converter including: a honeycomb structured body in which multiple through-holes are arranged longitudinally in parallel with one another with a partition wall therebetween; and a noble metal supported on the honeycomb structured body, wherein the honeycomb structured body contains a ceria-zirconia complex oxide and alumina, each partition wall includes a first carrier layer defining a surface layer of the partition wall and carrying Pd, and a second carrier layer located more inwardly of the partition wall than the first carrier layer and carrying Rh.

The present invention provides a honeycomb catalytic converter including: a honeycomb structured body in which multiple through-holes are arranged longitudinally in parallel with one another with a partition wall therebetween; and a noble metal supported on the honeycomb structured body, wherein the honeycomb structured body contains a ceria-zirconia composite oxide and alumina, and cerium on a surface of each partition wall has a lower concentration than cerium in a central portion of the partition wall in a thickness direction.

Methods for preparing ceria-zirconia (CZO) materials calcined with precious group metals (PGM) include calcining a CZO material with PGM. The calcined CZO/PGM catalyst is reduced at a temperature of ≥1000° C. to ≤1100° C. for a time of ≥0.5 hour to 1 hour to form a (CZO/PGM)-pyrochlore catalyst. The (CZO/PGM)-pyrochlore catalyst exhibits superior oxygen storage capacity characteristics as a three-way catalyst in vehicle exhaust gas systems.

A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first platinum group metal (PGM) component and a first oxygen storage capacity (OSC) material, wherein the first catalytic region has a washcoat porosity of less than 50%; and wherein the first OSC material has a pore: volume of at least 0.4 mL/g.

A catalyst article and its use in an exhaust system for internal combustion engines is disclosed. The catalyst article comprises a substrate which is a wall-flow filter, a first catalyst composition, and a second catalyst composition. The first and second catalyst compositions each independently comprise an oxygen storage component (OSC) derived from a CeZr mixed oxide sol having a D90 of less than 1.3 micron and a particulate inorganic oxide having a D90 of from 1 to 20 microns.

A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first palladium (Pd) component and a first Pd support material, wherein the substrate is substantially free of the first Pd component.