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Air quality improvement, especially in urban areas, is one of the major concerns for the coming years. For this reason, car manufacturers, equipment manufacturers and refiners have explored development issues to comply with increasingly severe anti-pollution requirements. In such a context, the identification of the most promising improvement options is essential. A research program, carried out by IFP (Institut Français du Pétrole), and supported by the French Ministry of Industry, IFP, PSA-Peugeot-Citroën, Renault and RVI (Renault Véhicules Industriels), has been built to study this point. It is based on a three years program with different steps focused on new engine technologies which will be available in the next 20 years in order to answer to more and more severe pollutant and CO2 emission regulations. This program is divided into three main parts: the first one for Diesel car engines, the second for Diesel truck engines and the third for spark ignition engines.

The evolution of European requirements for the reduction of spark ignited engine emissions makes necessary a better understanding of the impact of gasoline formulation on regulated, photochemical and toxic pollutants. To this end, the effects of gasoline have been studied on a European four-cylinder engine, fitted with a three-way catalyst and operated at steady state conditions. A design for experiments with mixtures made it possible to study the effects of different classes of gasoline compounds, using n-pentane, isopentane, 1-pentene, cyclohexane, n-octane, isooctane, toluene, ethylbenzene, m- and p-xylenes and o-xylene introduced in an alkylate base stock. Aromatics, especially the more substituted ones, produce the greatest engine-out hydrocarbon emissions. They also increase the nitrogen oxide emissions. However, both unburned hydrocarbon and tailpipe nitrogen oxide emissions are decreased with aromatics.