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: In an apparatus for reducing the nitrogen oxide emission of an internal combustion engine wherein the nitrogen oxides are removed from the engine exhaust gas in an adsorber from which they are subsequently purged by hot gases, the hot gases with the nitrogen oxides purged from the adsorber are returned to the air intake of the internal combustion engine for reaction in the combustion process in the internal combustion engine in which the nitrogen oxide is converted to nitrogen and oxygen.