Thermal stability breakpoint temperatures are shown for 32 jet fuels prepared from oil shale and coal syncrudes by various degrees of hydrogenation. Low severity hydrotreated shale oils, with nitrogen contents of 0.1 to 0.24 weight percent, had breakpoint temperatures in the 477 to 505 K (400 to 450 F) range. Higher severity treatment, lowering nitrogen levels to 0.008 to 0.017 weight percent, resulted in breakpoint temperatures in the 505 to 533 K (450 to 500 F) range. Coal derived fuels showed generally increasing breakpoint temperatures with increasing weight percent hydrogen, fuels below 13 weight percent hydrogen having breakpoints below 533 K (500 F). Comparisons are shown with similar literature data. Reynolds, T. W. Glenn Research Center NASA-TM-X-3551, E-9070 RTOP 505-04...

This project focuses on the compositional factors affecting high temperature thermal stability of coal-derived and petroleum-based jet fuels in pyrolytic regime. Thermal stability refers to the resistance of fuel to chemical decomposition at high temperatures to cause the solid deposition and liquid depletion. There are four broad objectives in this project, and the research work is divided into four tasks. The first task clarifies the chemistry of fuel degradation and mechanisms of solid formation, and identifying thermally stable classes of hydrocarbon compounds, and providing information for enhancing intrinsic stability of jet fuels. The second task involves characterization of the solids including deposits, sediments and gums produced from fuels and model compounds at high temperatures. The third task is to explore the means to enhance the thermal stability of fuels by examining the effects of various additives. The fourth task is a newly initiated exploratory study on conversion of coals to thermally stable jet fuels.