A theoretical study of JP-10 hydroperoxidation (original) (raw)
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Energy & Fuels, 2006
It is anticipated that future jet fuels will be required to handle a thermal stress of approximately 900°F (480°C). Such an environment presents many challenges in providing fuels with the necessary thermal oxidative and pyrolytic stability. We report single-tube flow reactor data which suggests that addition of 100 ppm of dicyclohexylphenyl phosphine (DCP) to an air saturated JP-8, followed by stressing up to ∼675°C, provides significant improvement in both thermal oxidative and pyrolytic stability. In addition, we present our current mechanistic understanding of how DCP might stabilize jet fuels under these extreme conditions. Finally, this work required us to reformulate the electron-transfer-initiated oxygenation (ETIO) mechanism proposed to explain the reaction of DCP with molecular oxygen.
Initiation Mechanisms and Kinetics of Pyrolysis and Combustion of JP-10 Hydrocarbon Jet Fuel
The Journal of Physical Chemistry A, 2009
In order to investigate the initiation mechanisms and kinetics associated with the pyrolysis of JP-10 (exotricyclo[5.2.1.0 2,6 ]decane), a single-component hydrocarbon jet fuel, we carried out molecular dynamics (MD) simulations employing the ReaxFF reactive force field. We found that the primary decomposition reactions involve either (1) dissociation of ethylene from JP-10, resulting in the formation of a C 8 hydrocarbon intermediate, or (2) the production of two C 5 hydrocarbons. ReaxFF MD leads to good agreement with experiment for the product distribution as a function of temperature. On the basis of the rate of consumption of JP-10, we calculate an activation energy of 58.4 kcal/mol for the thermal decomposition of this material, which is consistent with a strain-facilitated C-C bond cleavage mechanism in JP-10. This compares well with the experimental value of 62.4 kcal/mol. In addition, we carried out ReaxFF MD studies of the reactive events responsible for oxidation of JP-10. Here we found overall agreement between the thermodynamic energies obtained from ReaxFF and quantum-mechanical calculations, illustrating the usefulness of ReaxFF for studying oxidation of hydrocarbons. The agreement of these results with available experimental observations demonstrates that ReaxFF can provide useful insights into the complicated thermal decomposition and oxidation processes of important hydrocarbon fuels.
Energy & Fuels, 2007
JP-900 is a generic name representing a future jet fuel that will be required to handle the anticipated thermal stress of ∼900°F (482°C) for several hours. In the previous paper in this journal, we showed that the addition, to a JP-8 fuel, of model compounds structurally similar to those potentially derived from the hydrotreatment of refined chemical oil/light cycle oil (RCO/LCO) blends enhances both the thermal oxidative and pyrolytic stability in a flow rig under approximate JP-900 conditions. In this paper, we report model studies designed to clarify the mechanisms by which the model stabilizers (tetralin, R-tetralol, and R-tetralone) function at 250 and 425°C.
The journal of physical chemistry. A, 2010
exo-Tricyclo[5.2.1.0(2,6)]decane (TCD) or exo-tetrahydrodicyclopentadiene is the principal component of the high-energy density hydrocarbon fuel commonly identified as JP-10. Thermodynamic parameters for the parent TCD molecule and of all the tricyclodecyl radicals corresponding to the loss of hydrogen atoms from different carbons sites (TCD-Ri with i indicating the given carbon center) are determined using several density functional theory and G3MP2B3 and CBS-QB3 higher level composite computational chemistry methods. Five isodesmic work reactions, three involving bridged hydrocarbon reference molecules with similar ring strains, are employed to produce a cancelation of systematic calculation errors in evaluation of standard, gas-phase formation enthalpies at 298 K. Delta(f)H degrees (298) for TCD is found to be -19.5 +/- 1.3 kcal mol(-1), which is several kcal mol(-1) lower than the commonly used values. C(i)-H bond energies for corresponding TCD carbon sites are evaluated as foll...
Energy & Fuels, 2007
JP-900 is the generic name given to a future jet fuel that will be required to handle an anticipated thermal stress of ∼900°F (482°C) for several hours. We report flowing rig scouting results, under approximate JP-900 conditions, examining the effect on both oxidative and pyrolytic stability of the addition of a few volume percent of model refined chemical oil/light cycle oil (RCO/LCO)-derived compounds to a petroleum-derived JP-8. Tetralin, tetralone, and tetralol were used as model hydroaromatic compounds, which, in principle, can be obtained via the hydrotreatment of RCO/LCO blends. Our scouting results suggest that a jet fuel with improved heat sink capabilities could likely be formulated by adding 1% v/v of hydroaromatic compounds to JP-8.
The Journal of Physical Chemistry A, 2008
The enthalpies of formation and bond dissociation energies, D(ROO-H), D(RO-OH), D(RO-Ȯ ), D(R-Ȯ 2 ) and D(R-OOH) of alkyl hydroperoxides, ROOH, alkyl peroxy, RO, and alkoxide radicals, RȮ , have been computed at CBS-QB3 and APNO levels of theory via isodesmic and atomization procedures for R ) methyl, ethyl, n-propyl and isopropyl and n-butyl, tert-butyl, isobutyl and sec-butyl. We show that D(ROO-H) ≈ 357, D(RO-OH) ≈ 190 and D(RO-Ȯ ) ≈ 263 kJ mol -1 for all R, whereas both D(R-Ȯ O) and D(R-OOH) strengthen with increasing methyl substitution at the R-carbon but remain constant with increasing carbon chain length. We recommend a new set of group additivity contributions for the estimation of enthalpies of formation and bond energies.
Effect of Residual Oxygenated Functional Groups on the Behavior of Alternative Jet Fuel Properties
2018
The goal of this project is to identification of the nature and the content of the oxygenated compounds present in alternative jet fuels and to develop methods for the fast identification of these oxygenated compounds. The chemical composition and fuel properties of nine alternative jet fuels (named as AJF 1-9) and three commercial jet fuels (named as CJF 1, 2 and 3) were studied. The fuels were characterized by GC/MS, SEP-GC/MS (for quantification of oxygenated molecules), viscosity, density, water content, water solubility at O °C, carbonyl content, total acid number, elemental composition, calorific value, flash point, differential scanning calorimetry, and surface tension. The content of oxygenated compounds measured was in all the cases very low and comparable with the amount found in commercial jet fuels. Phenols are the most common trace oxygenated compounds found in aviation fuels.A new method based on the identification of extracted phenolic compounds by UV-fluorescence was...
Pyrolytic degradation studies of a coal-derived and a petroleum-derived aviation jet fuel
Energy & Fuels, 1993
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.