The present invention is directed to a catalyst system for the reduction of the harmful exhaust-gas constituents hydrocarbons (THC), carbon monoxide (CO), nitrogen oxides (NO.sub.x), and the environmentally detrimental secondary emissions ammonia (NH.sub.3) and nitrous oxide (N.sub.2O) of combustion engines operated using gasoline and to a corresponding method for exhaust-gas purification. The system is characterized by a particular arrangement of catalysts and is used in the case of engines which are operated with predominantly, on average, stoichiometric air/fuel mixtures. Here, a three-way catalyst produced in accordance with the current prior art is preferably installed in a close-coupled position. In the underfloor position, there is situated an SCR catalyst produced in accordance with the current prior art, followed by a further three-way catalyst produced in accordance with the current prior art. The three-way catalyst in the underfloor region furthermore has a lower oxygen-storing capacity than the close-coupled three-way catalyst.

The exhaust gas purification device according to the present invention includes a substrate of wall flow structure having a porous partition wall 16, and a catalyst layer held in internal pores of the partition wall 16. The catalyst layer contains, as a carrier, an OSC material having oxygen storage capacity. In the thickness direction of the partition wall 16, the porosity of the internal pores in inlet regions 16a is 25% or higher, and an average occupation ratio of the catalyst layer held in the internal pores is 75% or lower.

A catalytic converter includes a substrate (1) and a catalyst layer (3). The catalyst layer includes a bottom catalyst layer (4), a first top catalyst layer (6) and a second top catalyst layer (7). The second top catalyst layer is provided on a downstream side relative to the first top catalyst layer. The first top catalyst layer is made of a ceria-free zirconia composite oxide support and rhodium. The second top catalyst layer is made of a ceria-containing zirconia composite oxide support and rhodium. The first top catalyst layer has a length that is X % of the entire length of the substrate. The second top catalyst layer has a length that is 100?X % of the entire length of the substrate. A ratio of a density of rhodium in the first top catalyst layer to a density of rhodium in the second top catalyst layer is at least 1 and at most 3.

Method of making and filtration article comprising a plugged honeycomb filter body comprising: intersecting porous walls extending an axial length in an axial direction from a proximal end to a distal end of the honeycomb filter body and defining a plurality of axial channels comprised of inlet channels, which are plugged at the distal end of the plugged honeycomb filter body, and outlet channels, which are plugged at the proximal end of the plugged honeycomb filter body, the porous walls comprising: porous ceramic base portions with a plurality of pores and an average thickness and having inlet sides and outlet sides; inlet surfaces defining the inlet channels; outlet surfaces defining the outlet channels; and treated sides comprising hydrophobic material deposits disposed at one of the inlet sides or the outlet sides of the porous ceramic base portions.

An exhaust gas control system according to the present disclosure includes: a first exhaust gas control catalyst layer that controls an exhaust gas emitted from an internal combustion engine; and a second exhaust gas control catalyst layer that further controls the exhaust gas that has been controlled by the first exhaust gas control catalyst layer. The second exhaust gas control catalyst layer contains an oxygen storage material. The ratio of the amount (mmolCO.sub.2/m.sup.2) of base points per specific surface area (m.sup.2/g) of the oxygen storage material to the specific surface area is equal to or less than 4.5010.sup.5.

The present invention provides an exhaust gas purification catalyst including a base material 11 and a catalyst layer 20 provided on the base material 11. The catalyst layer 20 includes: a catalyst metal; and a carrying material 21 carrying the catalyst metal. The carrying material 21 includes: an OSC material 22 having an oxygen storage capacity; and a carrier 23 other than the OSC material. The OSC material 22 has a mean particle diameter Dx of 1.5 m or more which is larger than the mean particle diameter Dy of the carrier 23 other than the OSC material 22.

A catalytic converter apparatus for use in an exhaust system of an internal combustion engine includes a housing having a gas inlet and a gas outlet, and at least one catalytic substrate element disposed in the housing. The at least one substrate element is divided into a plurality of zones or sections, the zones at least partially separated from one another to inhibit heat flow. The zones can be at least partially separated with walls. The walls can include insulating material for reducing the mobility of heat radially outwardly. Each of the zones defines a generally separate flow passage connecting the inlet and outlet in fluid communication. The apparatus can heat more rapidly from a cold start compared with conventional catalytic converters.

Described are exhaust gas treatment systems for treatment of a gasoline engine exhaust gas stream containing NOx, particulate matter, and sulfur. The exhaust gas treatment system comprises: one or more catalytic articles selected from a three-way conversion catalyst (TWC), a lean NOx trap (LNT), and an integrated LNT-TWC; a platinum-containing catalytic article downstream from the one or more catalytic articles; and one or more selective catalytic reduction (SCR) catalytic articles immediately downstream from the platinum-containing catalytic article, the one or more SCR catalytic articles including a molecular sieve. The system stabilizes the SCR catalytic article from poisoning by sulfur.

Provided is an exhaust gas purification catalyst that combines reduction of pressure loss and enhancement of purification performance. This invention provides an exhaust gas purification catalyst comprising a wall-flow-type substrate and first and second catalytic layers. The first catalytic layer is provided to the interior of a partition wall, in contact with an entrance cell, from an exhaust inlet-side end in the running direction, having a length L1 less than Lw. The second catalytic layer is provided to the interior of a partition wall, in contact with an exit cell, from an exhaust outlet-side end in the running direction, having a length L2 less than Lw. An internal portion of partition wall in contact with entrance cell has a substrate-exposing segment near the exhaust outlet-side end.

A filtration article comprises inorganic deposits disposed at inlet sides of porous ceramic base portions of a plugged honeycomb filter body; and a catalytic material, e.g., a three-way conversion (TWC) catalytic material, disposed at outlet sides of porous ceramic base portions of the plugged honeycomb filter body. Interposing regions are located between the inlet sides and the outlet sides of the porous ceramic base portions. A majority or all of the inorganic deposits are spaced away from a majority of the catalytic material by the interposing region at a given axial location and/or across an entire axial length. The inorganic deposits and the porous ceramic base portions are not hydrophobic.