Characterization of gas and particulate phase organic emissions (C₉-C₃₇) from a diesel engine and the effect of abatement devices

Particulate and vapor phase emissions in the diluted exhaust of a light-duty diesel engine designed for Euro 5 application have been sampled. The engine was operated in three modes, and samples were collected from the exhaust without aftertreatment but also with aftertreatment by an exhaust oxidation catalyst and particle filter. The samples were analyzed by two-dimensional gas chromatography with time-of-flight mass spectral detection. The results show overall removal efficiencies for the organic compound mass by the combination of oxidation catalyst and particle filter of 50, 56, and 74% for the high-speed/high-load, low-speed/low-load, and high-speed/low-load conditions respectively. The results are clearly indicative of substantial repartitioning of the particulate and vapor components within the abatement devices and show an apparently reduced efficiency for the removal of high-molecular-weight alkanes under high-speed/high-load conditions relative to lower-molecular-weight compounds, although this may be due to alkane formation by thermocracking of other species. A notable feature is the presence of oxygenated compounds in the emissions, which are not present in the fuel. These are increased under high-speed/high-load conditions, and the results suggest the formation in the aftertreatment devices as well as in the combustion process.