Catalytic appts. for reducing nitrogen oxide(s) in I.C. engine exhaust - has catalyst bed of different materials active in different temp. ranges of exhaust gas

摘要

Catalytic appts. for reducing nitrogen oxides in an I.C. engine exhaust gas produced in a wide temp. range has at least two catalyst beds (7,8) of different materials arranged in the direction of the exhaust gas stream. The different materials have their strongest catalytic action in different regions of the temp. range of the exhaust gas. Specifically, an ammonia inlet is located in front of the first catalyst bed (7) in the direction of the exhaust gas. Catalyst bed (7), whose optimum activity lies in a higher temp. range, is located in the stream direction before bed (8). The catalyst material for the higher exhaust gas region is based on Fe2(SO4)3 and the catalyst material for the lower region on a mixt. of Ti02 and V205 or Fe203 and Cr203. A soot particle filter (3) with a temp. peak buffer (4) is connected to the bed (7). An oxidn. catalyst bed (9) is located after bed (8). ADVANTAGE - The appts. can be made to suit the characteristics of the exhaust gas stream of engines.