Abstract: An exhaust gas purifying catalyst comprises a powder including a porous material having a specific surface area of 150 m2/g or more, cerium and platinum. Cerium and Platinum are loaded on the porous material. The powder has platinum dispersion of 70% or more before baking and platinum dispersion of 50% or more after baking in air at 700° C. Additionally, a reduction rate R of the platinum dispersion after the baking against the platinum dispersion before the baking is below 40%.

Abstract: An exhaust gas purifying catalyst for purifying exhaust gas discharged from an automotive internal combustion engine. The exhaust gas purifying catalyst comprises at least one noble metal selected from the group consisting of platinum, palladium and rhodium; and boehmite alumina serving as a base material. In this exhaust gas purifying catalyst, nitrogen oxides in exhaust gas from the engine is trapped to the exhaust gas purifying catalyst when exhaust gas is in a lean region and is reduced into nitrogen by the exhaust gas purifying catalyst when exhaust gas is in a stoichiometric region or a rich region.

Abstract: An exhaust gas purifying catalyst comprises a catalytic ingredient including rhodium, at least one of platinum and palladium, at least one of absorption materials for absorbing NOx, a porous carrier, and a monolithic support for supporting the catalytic ingredient. The exhaust gas purifying catalyst includes a plurality of catalytic layers containing at least a part of the catalytic ingredient, and rhodium is contained at least in an outermost layer of the catalytic layers. A rhodium amount in the catalytic ingredient is 0.5 g or more for each liter of the catalyst, and a rhodium amount contained in the outermost layer accounts for 80 wt % or more of a total rhodium amount. A weight of the catalytic layer at the outermost layer is 40 wt % or below of a total weight of the catalytic layers.

Abstract: An exhaust gas purifying system for an internal combustion engine mounted on an automotive vehicle. The exhaust gas purifying system comprises an exhaust gas component concentration regulating device disposed in an exhaust gas passageway of the engine, for regulating concentrations of gas components in exhaust gas discharged from the engine such that the concentrations of carbon monoxide and hydrogen are respectively not more than 2.0% by volume and not less than 0.5 by volume and such that a volume concentration ratio of [hydrogen/carbon monoxide] is not smaller than 0.5, in rich and stoichiometric conditions of exhaust gas. Additionally, a NOx adsorbing and reducing catalyst is disposed in the exhaust gas passageway downstream of the exhaust gas component concentration regulating device, for adsorbing nitrogen oxides in a lean condition of the exhaust gas and reducing the nitrogen oxides into nitrogen in the rich and stoichiometric conditions.

Abstract: An exhaust gas purifying system for an internal combustion engine mounted on an automotive vehicle. The exhaust gas purifying system may include an exhaust gas component concentration regulating device disposed in an exhaust gas passageway of the engine, for regulating concentrations of gas components in exhaust gas discharged from the engine such that the concentrations of carbon monoxide and hydrogen are respectively not more than 2.0% by volume and not less than 0.5 by volume and such that a volume concentration ratio of hydrogen/carbon monoxide is not smaller than 0.5, in a first exhaust gas condition in which air/fuel ratio of exhaust gas is within a range of from a rich value and a stoichiometric value.

Abstract: An exhaust gas purifying catalyst for exhaust gas discharged from a lean-burn engine of an automotive vehicle. The catalyst comprises a refractory inorganic carrier. A catalytic layer is coated on the refractory inorganic carrier. The exhaust gas purifying catalyst layer contains platinum and at least one noble metal selected from the group consisting of palladium and rhodium, and a NOx trapping substance. In the catalytic layer, platinum exists close enough to the NOx trapping substance to accept NO2 from the NOx trapping substance which NO2 is produced according to reaction expressed by the following chemical equation: M(NO3)2→2NO2+3/2O2+MO where M is the NOx trapping substance.

Abstract: A NOx reduction catalyst for exhaust gas discharged from an automotive internal combustion engine operable in a lean region and in a range including a stoichiometric region and a rich region. The NOx reduction catalyst comprises a catalytic noble metal. Additionally, an oxygen adsorbable and releasable material is provided carrying at least a part of the catalytic noble metal. In this catalyst, the catalytic noble metal carried on the oxygen adsorbable and releasable material adsorbs SOx in the exhaust gas, in a form of at least one of sulfate and sulfite.

Abstract: An exhaust gas purifying catalyst for an internal combustion engine of an automotive vehicle. The exhaust gas purifying catalyst comprises a monolithic substrate. A first catalytic layer is formed on the monolithic substrate. The first catalytic layer contains at least one noble metal selected from the group consisting of rhodium, platinum and palladium, compound of at least one metal selected from the group consisting of alkali metal, alkaline earth metal and rare earth metal, and alumina. Additionally, a second catalytic layer is formed on the first catalytic layer and contains rhodium, at least one noble metal selected from the group consisting platinum and palladium, compound of at least one metal selected from the group consisting of alkali metal, alkaline earth metal and rare earth metal, and alumina. A content of the compound of the at least one metal in the second catalytic layer is larger than that in the first catalytic layer.

Abstract: A device (catalytic converter) for purifying an exhaust gas. This device has a first catalyst for purifying a NOx of the exhaust gas. This first catalyst contains first and second powders. The first powder has a porous carrier and at least one noble metal loaded on the porous carrier. The at least one noble metal is selected from platinum, palladium and rhodium. The second powder has a first double oxide represented by the general formula (Ln1-&agr;A&agr;)1-&bgr;BO&dgr; where &agr; is a number that is greater than 0 and less than 1, &bgr; is a number that is greater than 0 and less than 1, &dgr; is a number that is greater than 0, Ln is at least one first element selected from La, Ce, Nd and Sm, A is at least one second element selected from Mg, Ca, Sr, Ba, Na, K and Cs, and B is at least one third element selected from Fe, Co, Ni and Mn. The device is improved in capability of purifying NOx contained in an oxygen rich exhaust gas.

Abstract: An exhaust gas purifying system for an internal combustion engine mounted on an automotive vehicle. The exhaust gas purifying system comprises an exhaust gas component concentration regulating device disposed in an exhaust gas passageway of the engine, for regulating concentrations of gas components in exhaust gas discharged from the engine such that the concentrations of carbon monoxide and hydrogen are respectively not more than 2.0% by volume and not less than 0.5 by volume and such that a volume concentration ratio of [hydrogen/carbon monoxide] is not smaller than 0.5, in a first exhaust gas condition in which air/fuel ratio of exhaust gas is within a range of from a rich value and a stoichiometric value.

Abstract: An exhaust gas purifying catalyst for purifying exhaust gas discharged from an automotive internal combustion engine. The exhaust gas purifying catalyst comprises at least one noble metal selected from the group consisting of platinum, palladium and rhodium; and boehmite alumina serving as a base material. In this exhaust gas purifying catalyst, nitrogen oxides in exhaust gas from the engine is trapped to the exhaust gas purifying catalyst when exhaust gas is in a lean region and is reduced into nitrogen by the exhaust gas purifying catalyst when exhaust gas is in a stoichiometric region or a rich region.

Abstract: An exhaust gas purifying system for an internal combustion engine of an automotive vehicle. The exhaust gas purifying system comprises an exhaust gas composition regulating device for producing a low HC concentration reducing agent in a lean exhaust gas atmosphere where air-fuel ratio is leaner than a stoichiometric value. The exhaust gas composition regulating device is disposed in an exhaust gas passageway of the engine. The low HC concentration reducing agent is low in concentration of hydrocarbons to have an exhaust gas composition having a volume ratio of NOx/HC not less than 50 in the exhaust gas passageway immediately downstream of the exhaust gas composition regulating device. Additionally, a NOx treating catalyst is disposed in the exhaust gas passageway and located downstream of the exhaust gas composition regulating device. The NOx treating catalyst is arranged to reduce NOx in the presence of the low HC concentration reducing agent supplied from the exhaust gas composition regulating device.

Abstract: An exhaust gas purifying system for an automotive internal combustion engine which discharges oxygen-excessive exhaust gas under lean-burn operation. The exhaust gas purifying system comprises a NOx reducing catalyst for reducing NOx in the presence of at least hydrogen serving as reducing agent. The NOx reducing catalyst is disposed in an exhaust gas passageway of the engine. The NOx reducing catalyst includes a porous substrate, and platinum and cesium carried on the porous substrate. A catalyst is disposed in the exhaust gas passageway in order to produce hydrogen so as to enrich the oxygen-excessive exhaust gas with hydrogen before the oxygen-excessive exhaust gas reaches the NOx reducing catalyst. The oxygen-excessive exhaust gas enriched with hydrogen is introduced through the exhaust gas passageway to the NOx reducing catalyst.

Abstract: The invention relates to a first catalyst for purifying an exhaust gas. The first catalyst has a substrate and a catalytic coating formed thereon. This catalytic coating has first and second grains. The first grain includes a porous carrier supporting thereon at least one of palladium and rhodium. The second grain includes a double oxide supporting thereon at least one of platinum and palladium. This double oxide is represented by a formula of (La.sub.1-x A.sub.x).sub.1-.alpha. BO.sub..delta. where A is at least one element selected from barium, potassium and cesium, B is at least one of iron, cobalt, nickel and manganese, 0<X<1, 0<.alpha.<0.2, and .delta. is a number such that a net electric charge of the first double oxide becomes zero. The invention further relates to a second catalyst similar to the first catalyst. The first grain of the second catalyst includes a porous carrier supporting thereon at least one of platinum, palladium, rhodium and iridium.

Abstract: A catalyst system for the purification of exhaust gas comprises at least two catalysts disposed on an exhaust system side of an engine and at least containing palladium as a catalyst component. In this case, each of catalysts disposed on upstream side and downstream side contains a given amount of an alkaline earth metal compound as an oxide conversion per 1 L of a carrier.