Thermal oxidative stability of coal-based JP-900 jet fuel: Impact on selected physical properties

The low-temperature oxidative stability of a fuel is determined by the potential for production of peroxides, leading to the formation of oxygenated products, change in color, and ultimately formation of sediment. The role of oxygenated products in determining the low-temperature physical properties of jet fuels has not been reported in the literature. The current study evaluates the impact of oxidative jet fuel stability on the following low-temperature properties: crystal size, crystal shape, freeze point, and viscosity.;It was found that over the range of oxidative conditions studied, compositionally similar products were produced for each fuel. Increasing the reaction temperature, between 50°C and 200°C, and pressure, between atmospheric and 200 psi, altered the quantity of oxidation products, but did not significantly shift the composition of these products. Major products observed in the oxidation of jet fuel samples included alcohols, ketones, and to a lesser extent acids.;The predominant crystal structures observed using cold-stage microscope techniques were small needle-like structures for cycloalkane-based fuels and large broad leaf-shaped structures for n-alkane-based fuels. The presence of oxidized compounds in the fuel samples decreased the overall size of the crystals and produced ribbon-shaped crystals in the n -alkane-based fuels. This was the result of the oxygenated functionalities of the polar compounds interrupting the regular alignment of molecules in the crystal structure.;Major differences in the freeze points of oxidized and unoxidized fuel samples were not observed. However, the viscosities of the oxidized fuel samples were found to be higher at all temperatures than the unoxidized fuel samples. The model of Coutinho et al. was found to be effective for predicting the freeze point of n-alkane-rich fuels, but failed to accurately predict the freeze point of cycloalkane-based hydrocarbons. A model by Cookson et al. was found to be effective for predicting the freeze point of a variety of fuel compositions in the jet fuel range, but collection of GC and NMR data.