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The reduction of diesel emissions will remain a major challenge in the near future. Based on the expected emissions legislation for Europe and NAFTA, respectively, two main routes to approach this challenge are possible. Especially for the NAFTA market the use of a NOx emission control system is highly probable due to the established low limit for NOx emissions. From today's point of view only two systems - the NOx storage catalyst and the SCR catalyst system - have the potential to reach these limits. In Europe the expected Euro5 NOx limit can most likely be reached by engine measures only. Nevertheless both markets have the common understanding that besides the further improvement by internal engine measures the diesel oxidation catalyst (DOC) as well as the catalysed diesel particulate (DPF) filter will play an essential role in diesel emissions reduction.

The launching of direct injection gasoline engines is currently one of the major challenges for the automotive industry in the European Union. Besides its potential for a notable reduction of fuel consumption, the engine with direct gasoline injection also offers increased power during stoichiometric and stratified operation. These advantages will most probably lead to a significant market potential of the direct injection concept in the near future. In order to meet the increasingly more stringent European emission levels (EURO IV), new strategies for the exhaust gas aftertreatment are required. The most promising technique developed in recent years, especially for NOx conversion in lean exhaust gases, is the so-called NOx storage catalyst.

Diesel particulate mass emissions and their corresponding size distributions have been investigated on a diesel passenger car at steady state conditions using standard filters and a cascade impactor. These tests have been carried out at two different engine operating conditions (2100 rpm, 2.7 and 13.3 kW, respectively) corresponding to low and high exhaust gas temperatures. Two diesel fuels differing in their sulfur content (150 ppm and 2500 ppm S) have been used for these investigations. The particulate size distribution after diesel oxidation catalyst was found to be affected by the sulfur content of the diesel fuel and by the exhaust gas temperature. Interpretations of these results on a mechanistic basis are given. The diesel particulate emission studies have been extended to dynamic vehicle tests.

The exhaust emissions from stoichiometric gas engines contain CO, Hydrocarbons and NOx besides CO2 and H2O. The Hydrocarbon emissions consist mostly of unburnt methane. Conventional Pt and Rh based three-way catalysts show a good performance for the conversion of CO and NOx at stoichiometric exhaust gas composition, but methane passes almost unconverted through the catalytic converter. At rich exhaust gas composition (Lambda = 0.995) higher conversion rates are achieved for methane, but the efficiency is still not satisfactory for instationary applications. Therefore specific catalyst formulations based on Pd were developed. Model gas reactor and first engine evaluation results are presented. The model gas data indicate that with Pd/Rh catalysts both a wider lambda window and a methane conversion of more than 90% can be achieved. Furthermore catalysts for lean burn applications were investigated.