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An overview is given on the state of the art of a new catalytic exhaust gas aftertreatment device for diesel engines. The function of a precious metal based, flow-through type diesel oxidation catalyst is explained. Much attention is paid to the durability of the diesel oxidation catalyst and especially to the influence of poisoning elements on the catalytic activity. Detailed data on the interaction of poisoning elements such as sulfur, zinc and phosphorus with the catalytic active sites are given. Finally it is demonstrated that it is possible to meet the stringent emission standards for diesel passenger cars in Europe with a new catalyst generation over 80.000 km AMA aging.

This paper reports first results of research and development work to achieve Nox reduction under lean diesel exhaust gas conditions by using a special coated, zeolite based monolith catalyst. Much attention is paid to the optimization of the activated zeolite system and the influence of group Ib and VIII elements of the periodic system. A major part of the paper deals with the influence of hydrocarbons, carbon monoxide, sulfur dioxide and water on the activity of the catalyst. Another aspect discussed is the influence of the residence time of the exhaust gas components. The thermal stability and the influence of poisoning elements on the catalyst performance is demonstrated by model gas reactor tests on oven and engine aged samples. Finally, first results on the performance of the catalyst system in a vehicle dynometer test are given.

Future emission standards for passenger cars are mainly aiming at a stringent reduction of their hydrocarbon (HC) emissions. A key factor to meet these requirements for passenger cars with otto engines and closed-loop three-way catalyst is the improvement of the cold-start behavior of the aftertreatment device. Amongst other concepts HC-adsorber systems have been proposed to cope with this problem. In the present paper, results of a fundamental research program on these molecular sieve adsorber systems are discussed. Model gas reactor experiments were used to select raw materials for hydrocarbon-adsorption capacity. The materials of choice were used either alone or in combination with state-of-the-art three-way catalysts; the performance of these systems was evaluated on two different vehicles according to the FTP 75 cycle. To get quantitative information about the nature of the stored HC, all investigations were supported by a detailed gas chromatographic HC-analysis.