Computational studies on the reactions of thiols, sulfides and disulfides with hydroperoxides. Relevance for jet fuel autoxidation

Density Functional Theory calculations (DFT) are reported on the reactions of hydroperoxides with different classes of sulfur: thiols (RSH), sulfides (RSR) and disulfides (RSSR), all of which are important trace species in the auto-oxidation of jet fuel. It is shown that thiols can react under auto-oxidation conditions with hydroperoxides to form sulfonic acids and alcohols. In contrast, it is shown that disulfide species are more likely to form thiyl radicals, which are less likely to be important for the direct autoxidation of fuels due to prohibitive reaction barriers. The reaction mechanisms reported here for sulfur oxidation and the associated calculated thermodynamic data can be used to extend the applicability of current chemical kinetic models for fuel autoxidation, which are currently treated as a single elementary reaction despite the range of sulfur species found in fuels.