This project focuses on the compositional factors affecting jet fuel thermal stability at high temperatures. The chemical composition of the four jet fuel samples (JP-8C, JP-8P, JP-7P, Jet A-1) and Wilsonville middle distillates was characterized by using selective ion monitoring technique in GC-MS analysis. The thermal treatment tests have been performed on jet fuels and a series of model compounds including tetralin, decalin, ethylcyclohexane, butylcyclohexane, n-butylbenzene, t-butylbenzene, n-octane, n-decane, and n-tetradecane. Deposit samples from an actual aircraft fuel system as well as those produced from jet fuels and model compounds in microautoclaves were characterized by FTIR and polarized-light microscopy. Experiments were conducted to find the optimum amount of antioxidant 2,6-di-tert-butyl-4-methylphenol necessary to minimize the solid formation upon thermal stressing of JP8 neat and Jet A-1 fuel samples. The chemistry of thermal degradation of the fuel and antioxidant mixtures was studied by using FTIR to characterize the liquid products from thermal stressing.

Model hydrocarbon compounds and jet fuels derived from both petroleum and coal liquids were thermally stressed in microautoclave reactors at temperatures of 350-500 degrees C. Regardless of starting material, alkylated benzenes, alkylated naphthalenes, biphenyls, and complex polycyclic aromatics are formed by this thermal stressing. The concentration of these intermediates depends on the starting material and the experimental conditions. The formation of solids is directly related to high concentrations of alkylbenzenes and polycyclic aromatics in the liquid phase. Solid products consist primarily of large polycyclic aromatics with varying aliphatic substitution and their composition depends on the compound and the thermal conditions. Analysis of the solids showed anisotropic structures consistent with pseudo-nematic liquid crystalline mesophase. From these experiments a preliminary ordering of compound stability based on structure has been established.(ttl).