THE ROLE OF HETEROATOMS IN JET FUEL INSTABILITY

ABSTRACT

The test fuel used in this investigation was a petroleum derived jet A fuel from Rastanura refinery, Saudi Arabia. The physical and chemical tests of fuel, and one month sunlight storage experiment exhibited the stability of fuel. Accelerated and ambient storage stability tests, conducted using model nitrogen compounds in jet-A fuel and n-decane, indicated that the rate of sediment formation was dependent on the structural features of nitrogen compounds and storage conditions. The pyrrole and indole derivatives did not produce any appreciable sediment except 2,6-dimethylpyrrole. Air, temperature, dissolved oxygen and light all strongly accelerate the process of sediment formation. On the other hand removal of dissolved oxygen significantly reduces it. Acids and phenols act respectively as accelerator and inhibitor towards sedimentation. The reaction has a low apparent activation energy and appears to involve a free radical oxidative self condensation of nitrogen compounds. The tower O/C ratios of sediment also supported the view point that oxidation is a key aspect of jet fuel thermal instability. Approximately 25 different types of possible structures were identified from average properties of sediments as analysed by elemental analysis, infrared and mass spectrometric methods.