Pyrolytic degradation studies of a coal-derived and a petroleum-derived aviation jet fuel

Abstract

The future high-Mach aircraft requires advanced jet fuel with high stability in rigorous thermal environments. In this work high-temperature thermal stability of two JP-8 type jet fuels, a petroleumderived JP-8P and a coal-derived JP-8C was studied by stressing in closed reactors at 450 °C under 0.7 MPa of N2 for periods ranging from 0.5 to 16 h. The extents of fuel degradation in terms of liquid depletion, gas formation, and solid deposition were always higher with JP-8P than with JP-8C.There appeared an induction period for solid formation, which was longer for JP-8C than for JP-8P. Tests with the saturates isolated chromatographically from these fuels indicated that JP-8C saturates are much more stable than the JP-8P saturates, and the higher stability of JP-8C is due to its composition. JP-8C is rich in one-to three-ring cycloalkanes and two-ring hydroaromatics, while JP-8P is composed mainly of long-chain paraffins. GC-MS provided valuable information on the relative stability and molecular transformation of hydrocarbon components in these jet fuels. Cycloalkanes were found to be more stable than long-chain paraffins with the same carbon number. The stability decreases with increasing length of main chain for the long-chain paraffins, or side chain for alkylcycloalkanes. Multisubstituted cycloalkanes are more stable than the monosubstituted ones with the same carbon number. Steric conformation of cycloalkanes also affects their reactivity; for decalin, the trans isomer was found to be more stable than the cis isomer. The higher stability of JP-8C can be attributed mainly to its higher content of cycloalkanes. Tetralins and decalins present in JP-8C also contribute to capping the thermally generated reactive radicals by hydrogen donation.

Coal-Based Fuel Formulation and Engineering

“…This is similar to results found for the coal-derived jet fuel JP8C at these temperatures and times. [5] However, gas formation is slightly higher than that observed from JP8C but still lower than that from the petroleum-derived jet fuel JP8P. [9] This indicates that the high content of cycloalkanes most likely prevents the formation of solids, whereas the relatively large concentration of linear/branched alkanes, such as in petroleum-derived JP8P, leads to a more dominant gas production when compared with the coal-derived jet fuel JP8C.…”

“…A volume of 5 ml was used, which was charged into a microautoclave with a total volume of 25 ml. [5] To remove entrapped air, the system was degassed 6 times with 1000 psi of ultra-high-purity N 2 (99.999%).…”

“…Previous research at PennState has established that a solution to this problem can be achieved using cycloalkane-rich fuels. [5,6] Coal-derived aviation jet fuels have been found to contain considerable amounts of cycloalkanes and indeed have shown superior thermal stability compared with petroleum-derived fuels which are rich in linear and branched alkanes. [7,8] Model compounds, such as linear alkanes and alkyl substituted ones, have been extensively studied at temperatures around 400-475 °C, where the superior stability of cycloalkanes, when compared with linear alkanes, has been confirmed.…”

Thermal stability and decomposition of diesel fuel under subcritical and supercritical conditions

“…Other studies have reported the effects of trace amounts of sulfur and nitrogen compounds and other contaminants such as metals [35,36], because these elements were found in large concentrations in deposits compared to fresh fuels [25]. A recent study reported that nitrogen and sulfur compounds were presented only in the liquid-phase product, but not in the solid phase deposits, and indicated that they did not aggregate during solid formation [34].…”

Refinery Integration of by-Products From Coal-Derived Jet Fuels

“…To meet the fuel performance and compositional specifications for diesel fuel, it is necessary for both RCO and LCO to be hydrogenated [43,44]. This work focuses on the development of increasingly sulfur-tolerant, noble-metal catalysts for the lowtemperature hydrotreating and dearomatization (LTHDA) of distillate fuels for the production of ultra-clean and low-aromatic diesel fuels.…”