Influence of the soluble organic fraction on the thermal behaviour, texture and surface chemistry of diesel exhaust soot

Diesel soot samples collected on a SiC filter while using or not an oxidation catalyst, were solvent extracted or heat treated under inert atmosphere. All studied soot were characterised by XPS, DRIFTS, TGA-MS, Py-GC-MS and gas sorption. In the first part, the obtained results are discussed in order to show the influence of an oxidation catalyst on some properties of the raw soot materials, such as their soluble organic fraction (SOF) content and composition, their surface chemistry and textural characteristics. Then, it is seen that the thermal decomposition of SOF adsorbed on the particulate matter leads under inert atmosphere to the formation of a microporous carbonaceous layer at 600 °C. On the other hand, textural analyses have revealed that the structure of the raw soot material is non-porous in nature, as subsequent extractions in DCM and toluene do not seem to create any porosity within the samples. Finally, we have described and discussed the composition of the particulate matter as a function of its respective components, namely SOF, volatile organic fraction (VOF), carbonaceous matrix and ashes.