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The particulate reduction targets imposed by regulations require wide knowledge about the effect of fuel formulation on both particulate emissions and composition. The results of a set of engine steady test-bed experiments, extraction procedures and chemical analysis are presented in this paper, aiming to study the effect of some of the main fuel properties on the particulate emissions and composition of a typical European passenger car Diesel engine. The tested fuels had different properties (density, volatility, cetane number, aromatic content, sulphur content, etc.), and also different engine operating conditions such as torque and engine speed, were tested.

Different extraction techniques have been analyzed when applied to the extraction of the soluble organic fraction from diesel particulate matter (DPM). It has been proved that a complete extraction (not frequently reached under conditions usually adopted in literature) is needed if a good characterization of both soluble and insoluble organic fraction is to be attained. Ultrasonication and microwave methods with mixtures of dichloromethane and benzene used as solvent lead to maximum extraction efficiency under two different conditions. Supercritical extraction with CO2 was also performed during 20 minutes in static state and 20 minutes in dynamic state, with similar results to these techniques. However, soxhlet extraction reaches higher efficiency, but only if the number of cycles and the solvent composition are carefully chosen. An incomplete extraction leads to misinterpretation of the SOF origin, since the oil contribution is not satisfactory considered.