Stability of radicals derived from oxygen-containing compounds detected in thermally unstable jet fuels

Jet fuel is a complex chemical mixture that contains thousands of individual compounds, and is essential for the propulsion and cooling of high-performance aircraft. When heated, certain heteroatom-containing compounds in jet fuel can react through free radical pathways to form insoluble deposits in fuel circulation systems. These deposits obstruct the flow of fuel through filters and nozzles, which leads to dangerous engine flameout that jeopardises aircraft performance and safety. Herein we quantify the stabilities of −C(=O)−O· radicals, C10H19O2· and C10H17O2·, derived from oxygen-containing compounds (OCCs) previously detected in thermally unstable jet fuels. The thermodynamic and kinetic contributions to radical stability are determined by density functional theory (DFT) and buried volume (Vbur) calculations, and used to compute radical stability scores (RSSs). Our results predict average RSSs in the range of 35–52, consistent with high chemical reactivity. These findings suggest that OCCs in jet fuels should be targeted for suppression through fuel additives or other mitigation techniques. This could potentially aid in reducing insoluble deposits in engine fuel circulation systems that form through autoxidative reaction pathways involving OCCs.