METHOD FOR SELECTIVE REDUCTION OF NITROXIDE

摘要

Process for reducing nitrogen oxides contained in a lean exhaust gas of an IC engine comprises selectively reducing the nitrogen oxides using ammonia on a reduction catalyst containing a zeolite exchanged with transition metals. A part of the nitrogen monoxide is reduced to nitrogen dioxide before the gas is fed together with the ammonia over a reduction catalyst. Oxidation of the nitrogen monoxide is carried out so that the exhaust gas contains 30-70 vol.% nitrogen dioxide before contact with the reduction catalyst. An Independent claim is also included or the process for the production of a reduction catalyst comprising forming an iron-exchanged zeolite, suspending with zirconyl nitrate in water, applying as a coating to a honeycomb body, and calcining the coating.