Elucidation of Oxygenated Intermediates from Naphthenic and Paraffinic Jet Fuels in the Autoxidative and Pyrolytic Regimes

摘要

Coal-based liquids have a great potential as precursors for advanced jet fuels that meet the more stringent thermal stability requirements for the future high-Mach jet aircraft (1,2). The cureent jet fuels are petroleum-derived and consequently rich in linear alkanes, which are highly susceptible to pyrolytic cracking resulting in coking (3,4). The thermal stability of a jet fuel in the pyroluytic regime can be greatly enhanced by utilizing liquids rich in cyclo-alkanes (5). This is case for hydrotreated coal-derived liquids, where the aromatic structures have been transformed over to their corresponding cycloalakanes (6). An additional problem with jet fuels is the presence of dissolved oxygen (from air). which reacts with the fuel during the autoxidative regime (150-250 deg C) before the fuel and its oxygenated reaction products enter the pyrolytic above 400 deg C (7). The effect of oxygen on linear alkanes has been well established, where the formation of peroxides promotes the autoxidative decomposition of the alkanes over to various liquid products and solid residues. However, little attention has been given to the behavior of cycloalkanes when heated through the autoxidative regime. In addition, scarce information is available on the fate of oxygenated compounds from both linear and cyclic alkanes as they go from the autoxidative to the pyrolytic regime, which the future jet fules are expected to experience. Accordingly, this paper compares the thermal of a linear alkane (tetradecane), a cycloalkane (decahydronaphthalene) and a coal-derived jet fuel as they go through the autoxidative regime into the pyroluytic regime. The differences in chemical reactivity between the linear-and cycloalkane have been related to the stability of the coal-derived jet fuel. Generally, the cycloalkane showed a lower tendency to form oxygenated compounds during the autoxidative regime compared to that of the linear alkane.