Structural effects on the oxidation of soot particles

Soot particles comprise of polycyclic aromatic hydrocarbons (PAHs), which have either planar or curved structures. The oxidation behaviors of soot particles differ depending on their structures, arrangement of PAHs, and the type of surface functional groups. To understand the role that PAH structure plays in soot reactivity towards O₂, experimental studies are conducted on two types of commercially produced soot, Printex-U and Fullerene soot, using high resolution transmission electron microscopy, electron energy loss spectroscopy, thermo-gravimetric analysis and elemental analysis. The relative concentrations of active sites, oxygenated functional groups, aliphatics and aromatics present in soots are evaluated. The activation energies for soot oxidation at different conversion levels are determined. The average activation energies of the two soots are found to differ by 26 kJ/mol. This indicates that the presence of curvatures in soot can significantly enhance the rate of soot oxidation at moderate temperatures (< 800°C) which are frequently used for the regeneration of diesel particulate filters.