The present invention relates to an ammonia oxidation catalyst for the treatment of an exhaust gas stream, the catalyst comprising a coating disposed on a substrate, wherein the coating comprises a selective catalytic reduction component being a zeolitic material comprising one or more of copper and iron; and an oxidation catalytic component comprising platinum supported on a porous non-zeolitic oxidic support, wherein the oxidation catalytic component further comprises a first oxidic material supported on the porous non-zeolitic oxidic support supporting platinum, wherein the first oxidic material comprises titania.

The presently claimed invention provides a layered catalytic article and an exhaust system. The catalytic article comprises a first layer comprising platinum, a first platinum group metal component other than platinum, a ceria-alumina composite, and an oxygen storage component; wherein platinum is supported on the ceria-alumina component; the platinum group metal component is selected from palladium, rhodium or a combination thereof and the platinum group metal component is supported on the oxygen storage component; a second layer comprising a second platinum group metal component; and a refractory alumina component, an oxygen storage component or a combination thereof; wherein the second platinum group component is selected from platinum, palladium, rhodium or a combination thereof; and a substrate, wherein the amount of platinum is 10 to 80 wt. %, based on the total weight of platinum, palladium and rhodium. The presently claimed invention also provides a process for the preparation of a layered catalytic article and use of the catalytic article and the exhaust system for purifying a gaseous exhaust stream comprising hydrocarbons, carbon monoxide, and nitrogen oxides.

Disclosed is an exhaust gas purification catalyst with a multilayered structure including an ultra-thin layer with a thickness of 20 micrometers or less and containing Rh, Pd, or both as at least one precious metal component, and to a method of manufacturing the same. The method includes a step of forming an ultra-thin layer having a thickness of 20 micrometers or less as the top layer of the catalyst by applying a polymer coating solution containing a polymer having a functional group capable of chelating with the precious metal component(s) on the surface of the multilayer structure of the catalyst. The disclosed catalyst exhibits improved removal efficiency for THC, CO, and NOx contained compared to an existing thin film-type catalyst. Since the disclosed catalyst is coated with a thin coating layer containing at least a portion of precious metal components, the disclosed catalyst exhibits improved performance while using the same amount of precious metal components as in conventional catalysts.

An after treatment method is disclosed. The after treatment method may include: operating an engine at a lean air/fuel ratio; calculating an amount of NH.sub.3 stored in an SCR catalyst; calculating an amount of NOx which will flow into the SCR catalyst; determining whether conversion to a rich air/fuel ratio is desired; calculating, when the conversion to the rich air/fuel ratio is desired, a rich duration for which the rich air/fuel ratio is maintained and a target air/fuel ratio; and operating the engine at the target air/fuel ratio for the rich duration.

The present invention provides an exhaust gas purifying catalyst including a first catalyst layer (12). The first catalyst layer (12) includes a first section (14) and a second section (15) in an exhaust gas flow direction, the first section (14) being located on an upstream side in the exhaust gas flow direction relative to the second section (15). The first section (14) and the second section (15) both contain a catalytically active component including a specific element. A concentration of the specific element is higher in the first section (14) than in the second section (15). A concentration gradient of the specific element contained in the first section (14) in a thickness direction of the catalyst layer (12) is milder than a concentration gradient of the specific element contained in the second section (15) in the thickness direction.

The present invention relates to a VOC reduction system and a VOC reduction method that applies pulse type thermal energy to a catalyst to activate the catalyst and oxidizes and removes the VOC.

The present invention provides a tri-metallic layered catalytic article comprising a first layer comprising palladium supported on at least one of an oxygen storage component, and an alumina component; a second layer comprising platinum and rhodium, each supported on at least one of an oxygen storage component and a zirconia component; and a substrate, wherein the weight ratio of palladium to platinum is in the range of 1.0:0.4 to 1:2. The present invention also provides a process for preparing the tri-metallic layered catalytic article, an exhaust system for internal combustion engine and use of the tri-metallic layered catalytic article for purifying a gaseous exhaust stream.

An exhaust gas purifying catalyst includes: a wall-flow structure substrate including an inlet cell, an outlet cell, and a porous partition; a first catalyst layer formed inside the partition such that a thickness of the first catalyst layer is between 40% and 60%, inclusive, of an overall thickness T.sub.w of the partition; and a second catalyst layer formed inside the partition such that the second catalyst layer extends across an entire region of the partition in a thickness direction thereof.

There is provided an exhaust gas purification system that allows efficient purification of NOx present in exhaust gas emitted from an internal combustion engine. The exhaust gas purification system of the disclosure comprises a first exhaust gas purification device that purifies exhaust gas emitted from an internal combustion engine, wherein the atmosphere alternately switches between a reducing agent-excess atmosphere and an oxidizing agent-excess atmosphere with respect to the stoichiometric atmosphere, and a second exhaust gas purification device that further purifies the exhaust gas that has been purified by the first exhaust gas purification device, wherein the first exhaust gas purification device has a three-way catalyst, and the second exhaust gas purification device has an exhaust gas purifying catalyst that comprises an AMn.sub.2O.sub.4 spinel-type oxide support (A=Mg, Zn or Li) on which a precious metal is supported.

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.