title: Combined Experimental and Computational Study on the Unimolecular Decomposition of JP-8 Jet Fuel Surrogates. I. n-Decane (n-C10H22).
abstract: Exploiting a high temperature chemical reactor, we explored the pyrolysis of helium-seeded n-decane as a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) over a temperature range of 1100-1600 K at a pressure of 600 Torr. The nascent products were identified in situ in a supersonic molecular beam via single photon vacuum ultraviolet (VUV) photoionization coupled with a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). Our studies probe, for the first time, the initial reaction products formed in the decomposition of n-decane-including radicals and thermally labile closed-shell species effectively excluding mass growth processes. The present study identified 18 products: molecular hydrogen (H2), C2 to C7 1-alkenes [ethylene (C2H4) to 1-heptene (C7H14)], C1-C3 radicals [methyl (CH3), vinyl (C2H3), ethyl (C2H5), propargyl (C3H3), allyl (C3H5)], small C1-C3 hydrocarbons [methane (CH4), acetylene (C2H2), allene (C3H4), methylacetylene (C3H4)], along with higher-order reaction products [1,3-butadiene (C4H6), 2-butene (C4H8)]. On the basis of electronic structure calculations, n-decane decomposes initially by C-C bond cleavage (excluding the terminal C-C bonds) producing a mixture of alkyl radicals from ethyl to octyl. These alkyl radicals are unstable under the experimental conditions and rapidly dissociate by C-C bond β-scission to split ethylene (C2H4) plus a 1-alkyl radical with the number of carbon atoms reduced by two and 1,4-, 1,5-, 1,6-, or 1,7-H shifts followed by C-C β-scission producing alkenes from propene to 1-octene in combination with smaller 1-alkyl radicals. The higher alkenes become increasingly unstable with rising temperature. When the C-C β-scission continues all the way to the propyl radical (C3H7), it dissociates producing methyl (CH3) plus ethylene (C2H4). Also, at higher temperatures, hydrogen atoms can abstract hydrogen from C10H22to yield n-decyl radicals, while methyl (CH3) can also abstract hydrogen or recombine with hydrogen to form methane. These n-decyl radicals can decompose via C-C-bond β-scission to C3 to C9 alkenes.
authors.affiliation: Department of Chemistry, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.
authors.forename: Long
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.
authors.forename: Tao
authors.identifier: http://orcid.org/0000-0003-4101-2385
authors.initials: T
authors.lastname: Yang
authors.affiliation: Department of Chemistry, University of Hawaii at Manoa , Honolulu, Hawaii 96822, United States.
authors.forename: Ralf I
authors.identifier: http://orcid.org/0000-0002-7233-7206
authors.initials: RI
authors.lastname: Kaiser
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Tyler P
authors.initials: TP
authors.lastname: Troy
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Musahid
authors.initials: M
authors.lastname: Ahmed
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States.
authors.forename: Daniel
authors.initials: D
authors.lastname: Belisario-Lara
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States.
authors.forename: Joao Marcelo
authors.initials: JM
authors.lastname: Ribeiro
authors.affiliation: Department of Chemistry and Biochemistry, Florida International University , Miami, Florida 33199, United States.
authors.forename: Alexander M
authors.identifier: http://orcid.org/0000-0002-7233-3133
authors.initials: AM
authors.lastname: Mebel