In major parts of the world legislation is presently in effect which aims at limiting the tailpipe emission of carbon monoxide, hydrocarbons and nitrogen oxides from internal combustion engines. The legislation was such that until recently mainly fuel powered otto engines needed a reduction of the amount of these components in the tailpipe exhaust gas. This was achieved by a variety of means, of which the incorporation of the closed loop controlled three-way catalyst became a widespread accepted technology. Recently, however, the environmental concern also turned to the tailpipe emission of internal combustion engines operating according to the diesel principle. This paper gives an overview gives an overview of the kind and origin of tailpipe emissions from diesel engines, on their impact on the environment and on the state of the art of catalytic exhaust gas aftertreatment devices. With diesel oxidation catalysts the particulate matter of the exhaust gas can be decreased to 40-50% whereas first results with precious metal containing Cu/ZSM-5-type catalysts have the potential to reduce nitrogen oxide emissions by approx. 35% under lean exhaust gas conditions. (A)
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