A three-way catalyst is disclosed. The three-way catalyst comprises a palladium component comprising palladium and a ceria-zirconia-alumina mixed or composite oxide, and also comprises a rhodium component comprising rhodium and a zirconia-containing material. The palladium component and the rhodium component are coated onto a silver-containing extruded molecular sieve substrate. The invention also includes an exhaust system comprising the three-way catalyst. The three-way catalyst results in improved hydrocarbon storage and conversion, in particular during the cold start period.

Systems, apparatus and methods are provided for reducing reductant consumption in an exhaust aftertreatment system that includes a first SCR device and a downstream second SCR device, a first reductant injector upstream of the first SCR device, and a second reductant injector between the first and second SCR devices. NOx conversion occurs with reductant injection by the first reductant injector to the first SCR device in a first temperature range and with reductant injection by the second reductant injector to the second SCR device when the temperature of the first SCR device is above a reductant oxidation conversion threshold.

A control method for improving nitrogen oxide purification performance (NO.sub.x) includes starting NO.sub.x regeneration, comparing first and second lambda values measured at first and second lambda sensors in a control unit, checking the lean NO.sub.x trap (LNT) temperature, and measuring a second time that has elapsed after the first and second lambda values are found to be the same, and checking whether the second time is greater than or equal to a predetermined time when it is observed that the temperature of the LNT is greater than or equal to the predetermined temperature value.

An exhaust system for an internal combustion engine, the exhaust system comprising, a lean NO.sub.x trap, a NO.sub.x storage and reduction zone on a wall flow monolithic substrate having a pre-coated porosity of 50% or greater, the NO.sub.x storage and reduction zone comprising a platinum group metal loaded on one or more first support, the or each first support comprising one or more alkaline earth metal compound, and a selective catalytic reduction zone on a monolithic substrate, the selective catalytic reduction zone comprising copper or iron loaded on a second support, the second support comprising a molecular sieve.

An internal combustion engine, wherein a hydrocarbon supply valve (15) and an exhaust gas purification catalyst (13) are disposed inside an engine exhaust gas passage. When an increase in the temperature of the exhaust gas purification catalyst (13) caused by hydrocarbons supplied from the hydrocarbon supply valve (15) is smaller than a predetermined increase amount, and a decrease in the pressure of fuel supplied to the hydrocarbon supply valve (15) when the hydrocarbons have been injected from the hydrocarbon supply valve (15) is larger than a predetermined decrease amount, the present invention determines that a blockage is occurring in a hydrocarbon injection channel (69) when the hydrocarbons have been injected from the hydrocarbon supply valve (15).

A NO.sub.x absorber catalyst for treating an exhaust gas from a diesel engine. The NO.sub.x absorber catalyst comprises a first NO.sub.x absorber material comprising a molecular sieve catalyst, wherein the molecular sieve catalyst comprises a noble metal and a molecular sieve, and wherein the molecular sieve contains the noble metal; a second NO.sub.x absorber material comprising palladium (Pd) supported on an oxide of cerium; and a substrate having an inlet end and an outlet end.

A zoned catalyzed substrate monolith comprises a first zone and a second zone that are arranged axially in series. The first zone comprises a platinum group metal loaded on a support and a first base metal oxide or a first base metal loaded on an inorganic oxide. The first base metal oxide is iron oxide, manganese oxide, copper oxide, zinc oxide, nickel oxide, or mixtures thereof. The first base metal is iron, manganese, copper, zinc, nickel, or mixtures thereof. The second zone comprises copper or iron loaded on a zeolite and a second base metal oxide or a second base metal loaded on an inorganic oxide. The second base metal oxide is iron oxide, manganese oxide, copper oxide, zinc oxide, nickel oxide, or mixtures thereof. The second base metal is iron, manganese, copper, zinc, nickel, or mixtures thereof. The second base metal is different from the first base metal.

An exhaust gas post-processing system includes an oxidation catalyst configured to oxidize substances included in the exhaust gas; a diesel particulate filter configured to collect particulate matters included in the exhaust gas and disposed subsequent to the oxidation catalyst; a dosing module configured to inject a reducing agent and disposed subsequent to the diesel particulate filter; and a selective catalytic reduction configured to remove nitrogen oxide using the reducing agent included in the exhaust gas and disposed subsequent to the dosing module. The diesel particulate filter includes a catalytic component represented by La.sub.1-xAg.sub.xMnO.sub.3 (where 0<x<1).

A high-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkali metal is supported, and a low-temperature NOx occlusion reduction type catalyst in which an NOx occlusion material containing an alkaline earth metal is supported, are disposed in series on an upstream side and a downstream side, respectively, of an exhaust gas purification system. An oxidation catalyst is disposed on an upstream side of the high-temperature NOx occlusion reduction type catalyst. The desulfurization of the NOx occlusion reduction type catalysts is facilitated, and the NOx reduction efficiency is improved by the partial oxidation of hydrocarbons in the exhaust gas, while a wide NOx active temperature window is achieved.

A decrease in an NOx removal or reduction rate at the time of filter regeneration is suppressed. To this end, provision is made for an NOx selective reduction catalyst, a filter arranged at the upstream side of the NOx selective reduction catalyst, an NH.sub.3 generation catalyst arranged at the upstream side of the NOx selective reduction catalyst to generate NH.sub.3 when the air fuel ratio of an exhaust gas is equal to or less than a stoichiometric air fuel ratio, a regeneration unit to carry out regeneration of the filter, and a generation unit to make the air fuel ratio of the exhaust gas equal to or less than the stoichiometric air fuel ratio, thereby causing NH.sub.3 to be generated in the NH.sub.3 generation catalyst, wherein the regeneration unit inhibits the regeneration of the filter until the generation of NH.sub.3 by the generation unit is completed.