Abstract: A method and apparatus for purifying an exhaust gas of an internal combustion engine includes an ammonia generating catalyst for generating ammonia from nitrogen oxides contained in the exhaust gas to be purified, and a nitrogen oxide reducing catalyst downstream of the ammonia generating catalyst, for reduction of nitrogen oxides contained in the exhaust gas to be purified. Generated ammonia is used as the reducing agent. A nitrogen oxide adsorption catalyst is arranged upstream of the ammonia generating catalyst, or the ammonia generating catalyst is arranged in an exhaust pipe branch which pertains to only a part of several separately controllable internal-combustion sources. One or more additional exhaust pipe branches assigned to the other internal-combustion sources and lead to the nitrogen oxide reducing catalyst, while bypassing the ammonia generating catalyst.

Abstract: An internal-combustion engine includes an engine control system that permits a change-over between a lean operation and a rich operation of the internal-combustion engine, and an exhaust gas purification system. A &lgr;-probe, an SOx storage catalyst and an NOx storage catalyst are successively arranged in an exhaust gas line behind the engine. At the start of desulfurization of the SOx storage catalyst, a change-over takes place from the lean to the rich operation of the engine. Secondary air is fed into the exhaust gas line; a predetermined &lgr; value of the exhaust gases mixed with secondary air and a temperature in the SOx storage catalyst are measured. At the end of the desulfurization, a change-over takes place from the rich to a lean operation of the engine.

Abstract: An emission control system for an internal-combustion engine has at least one nitrogen oxide adsorber for the periodic adsorption and desorption of nitrogen oxides contained in the exhaust gas of the internal-combustion engine. A desorption gas pipe has an externally heatable catalyst arranged therein to which a mixture of air and/or exhaust gas can be fed as well as fuel at an at least stoichiometric proportion. This mixture is burned to form a desorbing gas flow which is fed to the respective nitrogen oxide adsorber for the nitrogen oxide desorption.

Abstract: An internal-combustion engine system includes an internal-combustion engine with a pertaining engine exhaust gas system, an emissions control device having an NO.sub.x storage catalyst arranged in the exhaust gas system, a lambda probe for detecting the engine air ratio and devices for the periodic desulfurization of the catalyst at a raised temperature and a rich air ratio of the latter, as well as to an operating process suitable for this system. The desulfurization devices comprise secondary air feeding devices for feeding secondary air into the NO.sub.x storage catalyst. During the desulfurization phases, the engine is operated at a rich air ratio and secondary air is metered into the catalyst.

Abstract: A multi-cylinder air-compressing injection-type internal-combustion engine having a nitric oxide adsorber catalyst and an exhaust gas return device. In order to increase the hydrocarbon fraction in the exhaust gas in front of an exhaust gas aftertreatment device during a regeneration phase and to reduce the oxygen content, exhaust gas pipes of the cylinders are divided into at least two flows, which extend separately from one another at least along a distance. An increased hydrocarbon emission is generated exclusively in the cylinders of one of the flows at times. Another of the flows is connected by way of the exhaust gas return device with an air intake pipe of the internal-combustion engine.

Abstract: An internal-combustion engine includes an engine control system that permits a change-over between a lean operation and a rich operation of the internal-combustion engine, and an exhaust gas purification system. A .lambda.-probe, an SO.sub.x storage catalyst and an NO.sub.x storage catalyst are successively arranged in an exhaust gas line behind the engine. At the start of desulfurization of the SO.sub.x storage catalyst, a change-over takes place from the lean to the rich operation of the engine. Secondary air is fed into the exhaust gas line; a predetermined .lambda. value of the exhaust gases mixed with secondary air and a temperature in the SO.sub.x storage catalyst are measured. At the end of the desulfurization, a change-over takes place from the rich to a lean operation of the engine.

Abstract: A method for operating a multicylinder internal combustion engine with at least one adsorber catalytic converter in the exhaust line of the internal combustion engine includes operating the adsorber catalytic converter with periodically alternating adsorption and desorption operation. The exhaust leaving the adsorber catalytic converter in desorption operation is recycled and/or an oxidation catalytic converter is provided upstream of the adsorber catalytic converter. Exhaust recycling takes place occurs selectively in only one set of the cylinders of the internal combustion engine and this set of cylinders is operated in a state of incomplete combustion during desorption operation. Rich afterburning may be performed during desorption operation of the adsorber catalytic converter in the oxidation catalytic converter connected upstream and the oxidation catalytic converter is operated at an increased temperature during short regeneration phases to remove soot.

Abstract: A motor vehicle exhaust emission control system has two adsorber parts connected in parallel for alternate adsorption and desorption of nitrogen oxides contained in the exhaust from an internal combustion engine and components for conducting further downstream the exhaust that emerges in the adsorber part that is operating at any given time in the adsorption mode and for returning the exhaust that emerges from the other adsorber part that is then operating in the desorption mode, to an intake line of the engine. An oxidizing converter is located upstream of the adsorber part and near the engine for oxidation of the NO contained in the exhaust to form NO.sub.2, so as to permit an increase in the NO.sub.X adsorption rate for the nitrogen adsorber parts.

Abstract: A process and apparatus for the selective catalyzed NO.sub.x reduction in oxygen-containing exhaust gases of internal-combustion engines. For improving the reduction of nitric oxides, hydrocarbons and air are supplied to the exhaust gas purifier and, for producing reactive short-chained unsaturated hydrocarbons, a defined quantity of fuel from the stored fuel intended for the fuel supply of the internal-combustion engine is catalytically cracked and is oxidized by the simultaneous supply of air. The resulting species are guided into the exhaust gas flow of the exhaust gases which are to be purified.

Abstract: A method and an apparatus reduces particles in exhaust gases of an internal combustion engine by passing the exhaust gases through a microwave energy field in a resonator for applying energy and burning the particles. In order to improve the application of energy, the particles are agglomerated beforehand in a high-voltage field of an electrostatic filter.