An object of the present invention is to provide an exhaust gas purification system including a first exhaust gas treatment section provided upstream in an exhaust pathway of an internal-combustion engine, a second exhaust gas treatment section provided upstream in the exhaust pathway of the internal-combustion engine, wherein the exhaust gas purification system allows rhodium element contained in a catalyst layer of the second exhaust gas treatment section to efficiently exhibit the catalytic activity, and the present invention provides an exhaust gas purification system (1) configured to purify exhaust gas emitted from an internal-combustion engine, the exhaust gas purification system (1) including an exhaust gas path (2) through which exhaust gas flows, a first exhaust gas treatment section (3) provided upstream in the exhaust gas path (2), and a second exhaust gas treatment section (4) provided downstream in the exhaust gas path (2); wherein first catalyst layers of the first exhaust gas treatment section (3) each contain cerium element; wherein a percentage of the mass of the cerium element contained in the first catalyst layers in terms of cerium oxide, to the mass of the first catalyst layers, is 5.0% by mass or more and 13.0% by mass or less; and wherein second catalyst layers of the second exhaust gas treatment section (4) each contain rhodium element.

An object of the present invention is to provide an exhaust gas purification system including a first exhaust gas treatment section provided upstream in an exhaust pathway of an internal-combustion engine, a second exhaust gas treatment section provided upstream in the exhaust pathway of the internal-combustion engine, wherein the exhaust gas purification system allows rhodium element contained in a catalyst layer of the second exhaust gas treatment section to efficiently exhibit the catalytic activity, and the present invention provides an exhaust gas purification system (1) configured to purify exhaust gas emitted from an internal-combustion engine, the exhaust gas purification system (1) including an exhaust gas path (2) through which exhaust gas flows, a first exhaust gas treatment section (3) provided upstream in the exhaust gas path (2), and a second exhaust gas treatment section (4) provided downstream in the exhaust gas path (2); wherein first catalyst layers of the first exhaust gas treatment section (3) each contain cerium element; wherein a percentage of the mass of the cerium element contained in the first catalyst layers in terms of cerium oxide, to the mass of the first catalyst layers, is 5.0% by mass or more and 13.0% by mass or less; and wherein second catalyst layers of the second exhaust gas treatment section (4) each contain rhodium element.

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, an outlet end with an axial length L; an inlet catalyst layer beginning at the inlet end and extending for less than the axial length L, wherein the inlet catalyst layer comprises an inlet palladium component; an outlet catalyst layer beginning at the outlet end and extending for less than the axial length L, wherein the outlet catalyst layer comprises an outlet rhodium component; and wherein the outlet catalyst layer overlaps with the inlet catalyst layer.

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, an outlet end with an axial length L; an inlet catalyst layer beginning at the inlet end and extending for less than the axial length L, wherein the inlet catalyst layer comprises an inlet palladium component; an outlet catalyst layer beginning at the outlet end and extending for less than the axial length L, wherein the outlet catalyst layer comprises an outlet rhodium component; and wherein the outlet catalyst layer overlaps with the inlet catalyst layer.

The present invention relates to a catalyst comprising two layers on an inert catalyst carrier, a layer A containing at least palladium as a platinum group metal, in addition to a cerium/zirconium/lanthanum/yttrium mixed oxide, and a layer B, which is applied to layer A, containing at least rhodium as the platinum group metal, in addition to a cerium/zirconium/lanthanum/yttrium mixed oxide.

The present invention relates to a molding catalyst and a method for producing the same, wherein the molding catalyst is used in the Deacon process for commercial production of chlorine using hydrogen chloride oxidation reaction, exhibits only a small reduction in catalytic activity even when exposed to harsh reaction conditions to thus be durable, and has superb mechanical strength to be suitable for use in a fixed bed catalytic reactor.

The present invention relates to a ruthenium precursor compound, and more particularly, to a ruthenium precursor compound which is for providing ruthenium to an ammonia decomposition reaction catalyst and is represented by Formula C.sub.xH.sub.yO.sub.zN.sub.mRu.sub.n, wherein x is an integer of 3 to 20, y is an integer of 0 to 32, z is an integer of 0 to 20, m is an integer of 0 to 10, and n is an integer of 1 to 3. In addition, the present invention relates to an ammonia reaction catalyst using the ruthenium precursor, and to a method for preparing the ammonia reaction catalyst, and provides an ammonia reaction catalyst having an excellent ammonia conversion rate at low temperatures, thereby being capable of efficient hydrogen production.

Disclosed are a composite oxide which is capable of maintaining a large volume of pores even used in a high temperature environment, and which has excellent heat resistance and catalytic activity, as well as a method for producing the composite oxide and a catalyst for exhaust gas purification employing the composite oxide. The composite oxide contains cerium and at least one element selected from aluminum, silicon, or rare earth metals other than cerium and including yttrium, at a mass ratio of 85:15 to 99:1 in terms oxides, and has a property of exhibiting a not less than 0.30 cm.sup.3/g, preferably not less than 0.40 cm.sup.3/g volume of pores with a diameter of not larger than 200 nm, after calcination at 900° C. for 5 hours, and is suitable for a co-catalyst in a catalyst for vehicle exhaust gas purification.

Disclosed are a composite oxide which is capable of maintaining a large volume of pores even used in a high temperature environment, and which has excellent heat resistance and catalytic activity, as well as a method for producing the composite oxide and a catalyst for exhaust gas purification employing the composite oxide. The composite oxide contains cerium and at least one element selected from aluminum, silicon, or rare earth metals other than cerium and including yttrium, at a mass ratio of 85:15 to 99:1 in terms oxides, and has a property of exhibiting a not less than 0.30 cm.sup.3/g, preferably not less than 0.40 cm.sup.3/g volume of pores with a diameter of not larger than 200 nm, after calcination at 900° C. for 5 hours, and is suitable for a co-catalyst in a catalyst for vehicle exhaust gas purification.

A exhaust gas purification apparatus is provided with: a substrate having a wall-flow structure and including entry-side cells, exit-side cells, and a porous partition; a first catalyst region formed in small diameter pores having relatively small pore diameters among internal pores in the partition; and a second catalyst region formed in large diameter pores having relatively large pore diameters among the internal pores in the partition. The first catalyst region contains a support and any one or two species of precious metal selected from Pt, Pd, and Rh loaded on the support, while the second catalyst region contains a support and any one or two species of precious metal selected from Pt, Pd, and Rh loaded on the support and other than at least the precious metal present in the first catalyst region.