AUTOXIDATION OF NEAT AND BLENDED AVIATION FUELS

The liquid-phase oxidation of eight fuels and a series of 1:1 blends h as been studied at elevated temperature and pressure to simulate some of the chemical-reaction conditions that cause surface fouling in airc raft fuel lines. The time, t, needed to deplete dissolved O-2 by 50% w as determined for each blend and component fuel. No simple relationshi p was found, i.e., linking t for blends and component fuels, attesting to the complexity of aviation-fuel autoxidation. about one-half of th e blends oxidize with t being intermediate between the two components. However, many blends between fuels of low thermal stability and fuels which have been severely hydrotreated are found to exhibit unusually slow oxidation, with t being greater than that measured for either com ponent. This phenomenon is not well understood; possible explanations focus on synergistic effects among natural antioxidants, dissolved met als, and aromatics in the blends. Measurements of surface fouling in b lends selected for their unusually slow oxidation indicate that therma l stability of fuels can be improved by blending with a paraffinic/cyc loparaffinic solvent. Improvements in thermal stability of 1:1 blends are comparable to those achieved by introducing conventional fuel addi tives.