Reduction process of nitrogen oxides and catalyst for use in this process

• Main Authors: KREUZER THOMAS DR, LOX EGBERT DR, SCHAFER-SINDLINGER ADOLF DR, SPURK PAUL DR, DEMEL YVONNE, PFEIFER MARCUS DR
• Format: Patent
• Language: Czech; English
• Published: 17.04.2002
• Edition: 7
• Subjects: BLASTING; CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOIDCHEMISTRY; CHEMISTRY; COMPOUNDS THEREOF; ENGINE PLANTS IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNALCOMBUSTION ENGINES; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES ORENGINES IN GENERAL; HEATING; INORGANIC CHEMISTRY; LIGHTING; MACHINES OR ENGINES IN GENERAL; MECHANICAL ENGINEERING; METALLURGY; NON-METALLIC ELEMENTS; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; SEPARATION; STEAM ENGINES; THEIR RELEVANT APPARATUS; TRANSPORTING; WEAPONS

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.