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Experimental work was carried out on a small displacement Euro 5 automotive diesel engine alternatively fuelled with ultra low sulphur diesel (ULSD) and with two blends (30% vol.) of ULSD and of two different fatty acid methyl esters (FAME) obtained from both rapeseed methyl ester (RME) and jatropha methyl ester (JME) in order to evaluate the effects of different fuel compositions on particle number (PN) emissions. Particulate matter (PM) emissions for each fuel were characterized in terms of number and mass size distributions by means of two stage dilutions system coupled with a scanning mobility particle sizer (SMPS). Measurements were performed at three different sampling points along the exhaust system: at engine-out, downstream of the diesel oxidation catalyst (DOC) and downstream of the diesel particulate filter (DPF). Thus, it was possible to evaluate both the effects of combustion and after-treatment efficiencies on each of the tested fuels.

Ceria nanofibers were synthesized as soot oxidation catalysts. The morphology of the catalyst was tailored to maximize the contact between the soot particles and the catalyst. Of the synthesized catalysts, the fibrous shape was the most active toward soot oxidation: the peak combustion temperature was reduced from 600°C (non-catalytic combustion) to 375°C during tight contact, 428°C during prolonged loose contact (see detailed definition in the text), and 553°C during loose contact. These results were compared to a very active ceria catalyst generated using the Solution Combustion Synthesis method and characterized by its high porosity and SSA surface.