A NO.sub.x adsorber catalyst composition, a NO.sub.x adsorber catalyst and its use in an emission treatment system for internal combustion engines, is disclosed. The NO.sub.x adsorber catalyst composition a support material and one or more platinum group metals disposed on the support material, wherein the support material comprises a mixed dopant NO.sub.x storage enhancer.

Methods and systems are featured for reducing harmful exhaust gas components of combustion devices such as gasoline-powered combustion engines (e.g., predominately stoichiometric running engines). The methods and systems include an underbody combination of a hydrocarbon trap (HCT), suited for cold start hydrocarbon adsorption, as well as an associated NOx trap. The system is inclusive of a control unit for extending a lean exhaust condition reaching the desorbing HCT as to avoid a deficiency in oxygen during the time period of HCT desorption. The system is also inclusive of one or more TWCs as in one associated with the underbody HCT-NOx-trap combination and/or one positioned in a close coupled position. Platinum group metals as in Pd, Rh and Pt are also featured on one, two or all three of the HCT, NOx-trap, and TWC when present.

An exhaust purification system is provided with a NOx-occlusion-reduction-type catalyst 32 that occludes NOx in exhaust when the exhaust is in a lean state and reduces and purifies the occluded NOx when the exhaust is in a rich state, and a NOx purge rich control unit 140 for reducing and purifying NOx occluded in the NOx-occlusion-reduction-type catalyst 32 by putting the exhaust into the rich state by repetitively performing fuel injection control of at least one of post injection and exhaust pipe injection at a predetermined interval.

There is provided a technology pertaining to abnormality diagnosis of an NSR catalyst that enables the diagnosis that the NSR catalyst is abnormal to be made even when the degree of deterioration of the NSR catalyst is relatively small yet. An abnormality diagnosis apparatus is applied to an exhaust gas purification apparatus having an NSR catalyst and a fuel addition valve. The abnormality diagnosis apparatus includes a controller configured to perform a specific fuel addition process and diagnose the NSR catalyst. The controller starts the specific fuel addition process when the NSR catalyst is in a specific start condition, and diagnoses the NSR catalyst on the basis of the quantity of NOx flowing out of the NSR catalyst over a specific period in the period from when the specific fuel addition process is started to when the temperature of the NSR catalyst reaches the thermal desorption temperature.

There is provided: a NOx-occlusion-reduction-type catalyst 32 that is provided in an exhaust passage 13 of an internal combustion engine 10; a NOx purge control unit 60 that performs a NOx purge control of setting the exhaust in the rich state and reducing and purifying NOx occluded in the NOx-occlusion-reduction-type catalyst 32; and a NOx purge inhibition processing unit 70 that inhibits NOx purge control when the internal combustion engine 10 becomes a motoring state in which fuel injection is stopped, and inhibiting, when the internal combustion engine 10 has started fuel injection during the inhibition of the NOx purge control, performance of the NOx purge control from the start of the fuel injection until a predetermined period of time has elapsed.

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.

An internal combustion engine 1 is provided, in an exhaust passage thereof with an electrochemical reactor including: an ion conductive solid electrolyte layer; an anode layer arranged on a surface of the solid electrolyte layer; and a cathode layer arranged on a surface of the solid electrolyte layer and able to hold NO.sub.X. The engine includes a current control device for controlling the current supplied to the electrochemical reactor so as to flow from the anode layer through the solid electrolyte layer to the cathode layer. The current control device is configured so as to supply current to the electrochemical reactor at least temporarily while that internal combustion engine is stopped.

The present invention relates to cerium oxide particles that have excellent heat resistance especially useful for catalysts, functional ceramics, solid electrolyte for fuel cells, polishing, ultraviolet absorbers and the like, and particularly suitable for use as a catalyst or co-catalyst material, for instance in catalysis for purifying vehicle exhaust gas. The present invention also relates to a method for preparing such cerium oxide particles, and a catalyst, such as for purifying exhaust gas, utilizing these cerium oxide particles.

A nitrogen oxides (NO.sub.x) and hydrocarbon (HC) storage catalyst for treating an exhaust gas flow is provided. The NO.sub.x and HC storage catalyst includes (a) a zeolite, (b) noble metal atoms, and (c) a metal oxide, a non-metal oxide, or a combination thereof. One or more of the noble metal atoms is present in a complex with the metal oxide, the non-metal oxide or a combination thereof. The complex is dispersed within a cage of the zeolite. Methods of preparing the NO.sub.x and HC storage catalyst and methods of using the NO.sub.x and HC storage catalyst for treating an exhaust gas stream flowing from a vehicle internal combustion engine during a period following a cold-start of the engine are also provided.

An object of the present disclosure is to provide an NO.sub.x storage material having sufficient NO.sub.x storage capacity even in a low temperature region and a production method thereof.

An NO.sub.x storage material including a composite oxide of silver and gallium. The composite oxide of silver and gallium is preferably a delafossite-type composite oxide. The composite oxide is produced by dissolving a silver salt and a gallium salt in a solvent and baking the solution, wherein the molar ratio of silver:gallium is preferably from 2:8 to 7:3.