A three-way catalyst article, and its use in an exhaust system for compressed natural gas engines, is disclosed. The catalyst article for treating exhaust gas from compressed natural gas (CNG) engine comprising: a substrate comprising an inlet end, an outlet end with an axial length L; a first catalytic region beginning at the outlet end and extending for less than the axial length L, wherein the first catalytic region comprises a first PGM component; and a second catalytic region beginning at the inlet end, wherein the second catalytic region comprises a second PGM component; wherein the first PGM component comprises palladium, platinum, or a combination thereof; and wherein the second PGM component comprises rhodium.

An exhaust gas purification catalyst provides excellent removal performance of methane, which is chemically stable. Exhaust gas purification catalyst includes a substrate that divides cells through which an exhaust gas flows and a catalyst layer that is provided on a surface of the substrate. The catalyst layer includes a palladium layer containing palladium that extends from a first end part which is an end part on the side into which an exhaust gas in the cells flows to a second end part which is an end part on the side from which an exhaust gas flows out, a platinum layer containing platinum that extends from the second end part to the first end part, and a rhodium layer containing rhodium that is laminated with both the palladium layer and the platinum layer.

An exhaust gas purification catalyst device having a substrate, a first catalyst coating layer on the substrate, and a second catalyst coating layer on the first catalyst coating layer. The first catalyst coating layer includes inorganic oxide particles, palladium carried on the inorganic oxide particles, and a barium compound. The second catalyst coating layer includes alumina particles and rhodium carried by the alumina particles. The ratio (M.sub.Ba/M.sub.Rh) between the mass (M.sub.Ba) of barium in the first catalyst coating layer and the mass (M.sub.Rh) of rhodium in the second catalyst coating layer is 5.0-60.0 inclusive.

An exhaust gas purification catalyst device has catalyst coating layers, which extend from the upstream side to the downstream side of the exhaust gas flow. The catalyst coating layers each have at least three zones present in order from the upstream side to the downstream side of the exhaust gas flow, and each of these at least three zones is an oxidation catalyst zone or a reduction catalyst zone. In the uppermost layer of an oxidation catalyst zone, the total number of atoms of platinum and palladium is greater than the number of atoms of rhodium; in the upper most layer of a reduction catalyst zone, the number of atoms of rhodium is greater than the total number of atoms of platinum and palladium. The oxidation catalyst zones and the reduction catalyst zones alternate at least twice in the exhaust gas flow direction.

Disclosed is a NOx-trapping catalyst having a non-platinum-group-metal NOx-trapping layer, which contains a transition metal, particularly manganese, able to maintain NOx-trapping performance while decreasing the amount of expensive platinum-group metal.

The presently claimed invention provides a tri-metallic layered catalytic article comprising: a) a top layer comprising platinum supported on at least one of an oxygen storage component, zirconia component and an alumina component, and rhodium supported on an oxygen storage component; b) a bottom layer comprising a front zone and a rear zone, said front zone comprising palladium supported on an oxygen storage component and an alumina component, and the rear zone comprises platinum supported on at least one of an alumina component, a ceria component, and an oxygen storage component; and c) a substrate, wherein the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1.0:2.0.

An oxidation catalyst for treating an exhaust gas from a diesel engine, which oxidation catalyst comprises: a first washcoat region comprising platinum (Pt), manganese (Mn) and a first support material; a second washcoat region comprising a platinum group metal (PGM) and a second support material; and a substrate having an inlet end and an outlet end; wherein the second washcoat region is arranged to contact the exhaust gas at the outlet end of the substrate and after contact of the exhaust gas with the first washcoat region.

Certain catalytic articles, systems or methods provide for excellent NOx conversion and are especially suitable for low temperature NOx conversion. The articles, systems and methods are suitable for instance for the treatment of exhaust gas of diesel engines. Certain articles or systems contain an upstream SCR composition and a downstream LNT composition. The substrate(s) may advantageously be electrically heated.

The present disclosure is directed to a method for treating a gaseous exhaust stream containing nitrogen oxides (NO.sub.x) from a diesel or lean-burn gasoline engine following a cold-start of the engine The method involves contact of the gaseous exhaust stream with at least a low temperature NO.sub.x adsorber (LT-NA) component. The LT-NA component includes a rare earth metal component, a platinum group metal (PGM) component, and a dopant. The present disclosure is also directed to a method of modulating a NO.sub.x adsorption/desorption profile of an LT-NA composition, a NO.sub.x desorption temperature range of an LT-NA composition, or both.

An exhaust gas purification catalyst for providing removal performance of methane, which is chemically stable includes a substrate that divides cells through which an exhaust gas flows and a catalyst layer that is provided on a surface of the substrate. The catalyst layer includes a palladium layer containing palladium that extends from a first end part which is an end part on the side of the cells into which an exhaust gas flows to a second end part which is an end part on the side from which an exhaust gas flows out, a platinum layer containing platinum that extends from the second end part to the first end part, and a rhodium layer containing rhodium that is laminated on both the palladium layer and the platinum layer.