Impact of Diesel Fuel Composition on Soot Oxidation Characteristics

The regeneration of a Diesel Particulate Filter (DPF) is dependent on both the amount and type of soot present on the filter. The objective of this work is to understand how the fuel can affect this ease with which soot can be oxidized. This soot was produced in a two-cylinder four-stroke direct-injection diesel engine, operated with a matrix of fuels with varying aromatic and sulphur level. Their oxidation behaviour in different environments was determined by Temperature Programmed Oxidation in TGA and a six-flow reactor. Transmission electron microscopy was used to examine the soot morphology.

Oxidation with only O₂ shows oxidation temperatures strongly dependent on the fuel type. Soot oxidation in the presence of NO and a Pt-catalyst results in a lower oxidation temperature. SO₂ has an inhibiting effect leading to higher soot oxidation temperature.

It was found that the amount of sulphur in the fuel has only a minor impact on the soot oxidation temperature, whereas aromaticity has a significant influence. A low aromatic fuel has a significantly higher oxidation temperature than high aromatic fuel; this will influence the DPF regeneration.