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To meet future emission levels the industry is trying to reduce tailpipe emissions by both, engine measures and the development of novel aftertreatment concepts. The present study focuses on a joint development of aftertreatment concepts for gasoline engines that are optimized in terms of the exhaust system design, the catalyst technology and the system costs. The best performing system contains a close-coupled catalyst double brick arrangement using a new high thermal stable catalyst technology with low precious metal loading. This system also shows an increased tolerance against catalyst poisoning by engine oil.

Engine and laboratory tests were carried out to examine the performance of NOx adsorption catalysts for gasoline lean burn engines in fresh and aged condition. The results show that fresh NOx adsorption catalysts have the potential to meet EURO III emission standards. However, to accomplish these the fuel must contain a low sulfur concentration and the engine must be tuned to optimize the efficiency of the catalyst. After engine or furnace aging upto 750°C the catalyst shows some loss of NOx adsorption efficiency. This deterioration can be offset somewhat by increasing the frequency of lean/rich switching of the engine. Temperatures higher than 750°C may cause an irreversible destruction of the NOx, storage features while the three-way activity of the catalyst remains intact or even may improve. With reference to several physicochemical investigations it is believed that the detrimental effect of catalyst aging is attributed to two different deactivation modes.

There is an increasing interest in running gasoline fueled passenger cars lean of stoichiometric air to fuel (A/F) ratio to improve fuel economy. These types of engines will operate at lean A/F ratios during cruising at partial load and return to stoichiometric or even rich conditions when more power is required. The challenge for the engine and catalyst manufacturer is to develop a system which will combine the high activity rates of a state-of-the-art three way catalyst (TWC) with the ability to reduce nitrogen oxides (NOx) under excess of oxygen. The target is to achieve the future legislation limits (EURO III/IV) in the European Union. Recent developments in automotive pollution control catalysis have shown that the utilization of NOx adsorption materials is a suitable way for reduction of NOx emissions of gasoline fueled lean burn engines.

The trend towards lower exhaust gas temperatures related to the introduction of modern, highly efficient diesel engines for passenger cars in conjunction with new legislative emission regulations will require the development of amended catalyst formulations. Not only excellent performance for carbon monoxide(CO), gaseous hydrocarbons (HC) and diesel particulates is desired but also the capability to additionally reduce nitrogen oxide (NOx) under lean conditions. Generally, as for the latter a passive system, i.e. without addition of secondary fuel, is most wanted but also an active system, i.e. with hydrocarbon enrichment before catalyst, could be successful provided the penalties in fuel consumption can be kept low. The present paper illustrates further progress in the area of diesel catalysts for passenger cars and introduces a novel washcoat formulation comprising zeolites as hydrocarbon adsorption components.

The paper describes research and development work concerning the investigation and optimization of lean NOx catalysts for gasoline and diesel engine applications. The investigations carried out in the laboratory, the engine bench and the chassis dynamometer demonstrate the influence of a number of important catalyst design parameters on the catalyst activity for nitrogen oxide reduction as well as for the conversion of carbon monoxide, gaseous hydrocarbons and in the case of diesel engine exhaust for particulates. In the first part of the paper significant improvements in catalyst activity and durability compared to the first catalyst generation are outlined. A major part of the paper deals with the influence of operation parameters such as space velocity and linear velocity of the reactants in the catalyst. Other aspects discussed are the influence of exhaust gas hydrocarbon component, active site distribution and poisoning elements affecting catalyst activity and durability.

To date, several non-SCR catalysts and catalytic systems have been suggested for NOX reduction under oxygen rich (lean) conditions, such as those which exist in diesel engine exhaust gas. However, the performance of such catalysts and catalyst systems is not clear when used on actual diesel engines. This paper reports on experimental results obtained when lean NOx catalysts are applied to diesel engine exhaust. Particularly, the catalysts' NOx performance is examined when secondary hydrocarbons are added as reducing agents directly in the exhaust gas stream. In addition, the effect of different catalyst formulations and secondary hydrocarbon addition on particulate emissions is monitored. Finally, partial system optimization is performed and the applicability of such catalysts and systems to engines operating under the US Heavy Duty Transient Cycle is examined.

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.

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.