Extended Liquid-Phase Oxidation of Aviation Fuels

Liquid-phase oxidation of two jet fuels classified as hydro-treated and straight-run (without dissolved metals) is studied at 185°C by measuring the depletion of dissolved oxygen in an isothermal, high-pressure flowing system. The goal is to simulate some of the effects of fuel recirculation by studying changes in oxidation that occur during the course of reaction. Recirculation of fuel is used in modem aircraft to optimize the ability of the fuel to dissipate heat from component systems. Following extended oxidation (prestressing), hydrotreated fuel oxidizes more rapidly than in its neat form resulting, in part, from formation of catalytic oxidation products such as hydroperoxides and depletion of synthetic primary antioxidants. In contrast, the straight-run fuel oxidizes more slowly following prestressing; this effect is ascribed to the formation of efficient secondary antioxidants and to depletion of radical initiators. Results are discussed in terms of changes in the distribution of primary and secondary antioxidants and their effect on subsequent oxidation and the thermal stability of recirculated fuel.