Thermal decomposition of cycloheptane was studied using flash pyrolysis coupled with vacuum ultraviolet (118.2 nm) single photon ionization time-of-flight mass spectrometry at temperatures ranging from 295 K to 1380 K. C-C bond breaking of cycloheptane leading to the 1,7-heptyl diradical was considered as the initiation step. The 1,7-heptyl diradical could readily isomerize to 1-heptene and decompose into several fragments, with dissociation to •C4H9 and •C3H5 as the predominant product channel. The 1,7-heptyl diradical could undergo direct dissociation, as evidenced by the production of the C5H10 species. Quantum chemistry calculations at UCCSD(T)/cc-pVDZ//UB3LYP/cc-pVDZ level of theory on the initial reaction pathways of cycloheptane were also carried out to support the experimental observations. Other possible initiation channels, as well as some secondary reaction products, were also identified.
HuberGWIborraSCormaA. Synthesis of transportation fuels from biomass: chemistry, catalysts, and engineering. Chem Rev2006; 106: 4044–4098.
2.
MastralAMCallénMS. A review on polycyclic aromatic hydrocarbon (PAH) emissions from energy generation. Environ Sci Technol2000; 34: 3051–3057.
3.
RanziECuociAFaravelliT, et al.Chemical kinetics of biomass pyrolysis. Energy Fuels2008; 22: 4292–4300.
4.
JinWPastor-PérezLShenD,et al.Catalytic upgrading of biomass model compounds: novel approaches and lessons learnt from traditional hydrodeoxygenation – a review. ChemCatChem2019; 11: 924–960.
5.
MoLYuWCaiH,et al.Hydrodeoxygenation of bio-derived phenol to cyclohexane fuel catalyzed by bifunctional mesoporous organic–inorganic hybrids. Front Chem2018; 6: 216.
6.
ShaoKLiuXJonesPJ, et al.Thermal decomposition of cyclohexane by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry: a study on the initial unimolecular decomposition mechanism. Phys Chem Chem Phys2021; 23: 9804–9813.
7.
YahyaouiMDjebaïli-ChaumeixNPaillardCE, et al.Experimental and modeling study of 1-hexene oxidation behind reflected shock waves. Proc Combust Inst2005; 30: 1137–1145.
8.
LiuXYuanWZhangJ,et al.Thermal decomposition of 1-hexene by flash pyrolysis: a study of initial decomposition mechanism. Proc Combust Inst2021; 38: 651–659.
9.
TsangW. Thermal stability of cyclohexane and 1-hexene. Int J Chem Kinet1978; 10: 1119–1138.
10.
AribikeDSSusuAAOgunyeAF. Mechanistic and mathematical modeling of the thermal decompostion of cyclohexane. Thermochim Acta1981; 51: 113–127.
11.
VoisinDMarchalAReuillonM,et al.Experimental and kinetic modeling study of cyclohexane oxidation in a JSR at high pressure. Combust Sci Technol1998; 138: 137–158.
12.
El BakaliABraun-UnkhoffMDagautP,et al.Detailed kinetic reaction mechanism for cyclohexane oxidation at pressure up to ten atmospheres. Proc Combust Inst2000; 28: 1631–1638.
13.
SteilUBraun-UnkhoffMNaumannC,et al.Experimental study of the pyrolysis of cyclohexane at shock tube relevant conditions. Proceedings of the European Combustion Meeting; Louvain-la-Neuve, Belgium April 3–6, 2005.
14.
KieferJHGupteKSHardingLB,et al.Shock tube and theory investigation of cyclohexane and 1-hexene decomposition. J Phys Chem A2009; 113: 13570–13583.
15.
WangZChengZYuanW, et al.An experimental and kinetic modeling study of cyclohexane pyrolysis at low pressure. Combust Flame2012; 159: 2243–2253.
16.
AribikeDSSusuAA. A review of mechanistic and mathematical modeling of n-heptane and cyclohexane pyrolysis. Appl Petrochem Res2018; 8: 193–201.
17.
Gusel'nikovLEVolkovaVVIvanovPE, et al.Direct infrared spectroscopic evidence of allyl radical and definition of the initiation step in thermal decomposition of cycloalkanes.: a comparison with very low pressure pyrolysis of alkenes. J Anal Appl Pyrolysis1991; 21: 79–93.
18.
SikesTBurdettKBSpethRL,et al.Ring opening in cycloheptane and dissociation of 1-heptene at high temperatures. Proc Combust Inst2021; 38: 929–937.
19.
GongC-MLiZ-RLiX-Y. Theoretical kinetic study of thermal decomposition of cyclohexane. Energy Fuels2012; 26: 2811–2820.
20.
SirjeanBGlaudePARuiz-LopezMF,et al.Detailed kinetic study of the ring opening of cycloalkanes by CBS-QB3 calculations. J Phys Chem A2006; 110: 12693–12704.
21.
ChambreauSDZhangJTraegerJC,et al.Photoionization of methyl t-butyl ether (MTBE) and t-octyl methyl ether (TOME) and analysis of their pyrolyses by supersonic jet/photoionization mass spectrometry. Int J Mass Spectrom2000; 199: 17–27.
22.
ShaoKTianYZhangJ. Thermal decomposition mechanism of allyltrichlorosilane and allyltrimethylsilane. Int J Mass Spectrom2021; 460: 116476.
23.
LiuXZhangJVazquezA,et al.Mechanistic study of thermal decomposition of hexamethyldisilane by flash pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry and density functional theory. J Phys Chem A2019; 123: 10520–8.
24.
KohnDWClaubergHChenP. Flash pyrolysis nozzle for generation of radicals in a supersonic jet expansion. Rev Sci Instrum1992; 63: 4003–4005.
25.
ShaoKTianYZhangJ. A mechanistic study of thermal decomposition of 1,1,2,2-tetramethyldisilane using vacuum ultraviolet photoionization time-of-flight mass spectrometry. J Phys Chem A2022; 126: 1085–1093.
26.
ChambreauSDZhangJ. VUV Photoionization time-of-flight mass spectrometry of flash pyrolysis of silane and disilane. Chem Phys Lett2001; 343: 482–488.
27.
ChambreauSDLemieuxJWangL,et al.Mechanistic studies of the pyrolysis of 1,3-butadiene, 1,3–butadiene-1,1,4,4-d4, 1,2-butadiene, and 2-butyne by supersonic jet/photoionization mass spectrometry. J Phys Chem A2005; 109: 2190–2196.
28.
GuanQUrnessKNOrmondTK,et al.The properties of a micro-reactor for the study of the unimolecular decomposition of large molecules. Int Rev Phys Chem2014; 33: 447–487.
29.
ShaoKBrunsonJTianY,et al.Flash pyrolysis mechanism of trimethylchlorosilane. Int J Mass Spectrom2022; 482: 116933.
30.
JonesPJRiserBZhangJ. Flash pyrolysis of t-butyl hydroperoxide and di-t-butyl peroxide: evidence of roaming in the decomposition of organic hydroperoxides. J Phys Chem A2017; 121: 7846–7853.
31.
WeberKHLemieuxJMZhangJ. Flash pyrolysis of ethyl, n-propyl, and isopropyl iodides as monitored by supersonic expansion vacuum ultraviolet photoionization time-of-flight mass spectrometry. J Phys Chem A2009; 113: 583–591.
32.
KrakaECremerD. Computer design of anticancer drugs. A new enediyne warhead. J Am Chem Soc2000; 122: 8245–8-64.
33.
SinhaPBoeschSEGuC,et al.Harmonic vibrational frequencies: scaling factors for HF, B3LYP, and MP2 methods in combination with correlation consistent basis sets. J Phys Chem A2004; 108: 9213–9217.
34.
EssDHJohnsonERHuX,et al.Singlet–triplet energy gaps for diradicals from fractional-spin density-functional theory. J Phys Chem A2011; 115: 76–83.
35.
ZieglerTRaukABaerendsEJ. On the calculation of multiplet energies by the Hartree-fock-slater method. Theor Chim Acta1977; 43: 261–271.
36.
Frisch GWTMJSchlegelHBScuseriaGE, et al.Gaussian 09. Wallingford, CT2009.
37.
Mass Spectra [Internet]. NIST Chemistry WebBook, NIST Standard reference database number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards and Technology, Gaithersburg MD, 20899,https://doi.org/10.18434/T4D303, (retrieved November 2, 2020).
38.
KostkoOBandyopadhyayBAhmedM. Vacuum ultraviolet photoionization of complex chemical systems. Annu Rev Phys Chem2016; 67: 19–40.
39.
NarendrapurapuBSSimmonettACSchaeferHF,et al.Combustion chemistry: important features of the C3H5 potential energy surface, including allyl radical, propargyl + H2, allene + H, and eight transition states. J Phys Chem A2011; 115: 14209–14214.
40.
RandazzoJBSivaramakrishnanRJasperAW,et al.An experimental and theoretical study of the high temperature reactions of the four butyl radical isomers. Phys Chem Chem Phys2020; 22: 18304–18319.
41.
KnyazevVDTsangW. Chemically and thermally activated decomposition of secondary butyl radical. J Phys Chem A2000; 104: 10747–10765.
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
