| Thermal decomposition of seven jet fuel model compounds, including n-decane, n-dodecane, n-tetradecane, n-butylbenzene, n-butylcyclohexane, decalin, and tetralin, was studied under near-critical and supercritical conditions in relation to future jet fuel thermal stability problems. The thermal reactions were carried out at 400-475{dollar}spcirc{dollar}C and 10-100 atm in a glass tube reactor and, in some cases, in a tubing bomb reactor.; Thermal decomposition of C{dollar}sb{lcub}10{rcub}{dollar} to C{dollar}sb{lcub}14{rcub}{dollar} n-alkanes under near-critical and supercritical conditions gave high yields of {dollar}rm Csb{lcub}3+{rcub}{dollar} n-alkanes and significant amounts of heavy alkanes which are usually not observed under low-pressure subcritical conditions. The pyrolyses of n-butylbenzene and n-butylcyclohexane were dominated by side-chain cracking. The formation of significant amounts of diphenylalkanes from pyrolysis of n-butylbenzene under supercritical conditions indicates that the reaction mechanism under these conditions is different from that under low-pressure subcritical conditions. The thermal decomposition of decalin and tetralin under high-pressure supercritical conditions was dominated by isomerization reactions. This is different from the results obtained under low-pressure and high-temperature conditions where cracking reactions (for decalin) or dehydrogenation reactions (for tetralin) dominate.; Pressure had significant effects on the product distributions and the apparent first-order rate constants in the near-critical regions of the model compounds. These large pressure effects can be attributed to the significant changes in density and possibly to the changes in the rate constants of elementary reactions with pressure in these regions.; Thermal decomposition of n-alkane mixtures was similar to that of pure n-alkanes, although individual n-alkanes interacted with each other in the thermal reactions of mixtures. The different thermal stabilities of a petroleum-derived jet fuel and a coal-derived jet fuel were attributed to the different compositions of these two fuels.; The critical temperatures of some petroleum-derived and coal-derived jet fuels were measured and estimated. Because of the shortcomings of the existing methods in estimating the critical temperatures of coal-derived jet fuels, a new correlation was proposed to calculate the critical temperatures of the coal-derived jet fuels. |
