Thermal Decomposition Kinetics and Mechanism of 1,1′-Bicyclohexyl
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Abstract
Thermal
decomposition of 1,1′-bicyclohexyl, a potential
surrogate component of high-density hydrocarbon fuels, was performed
in a batch-type reactor to investigate its thermal stability. A first-order
kinetic equation is supposed to correlate the decomposition process,
and the apparent rate constants, ranging from 0.0223 h<sup>–1</sup> at 683 K to 0.1979 h<sup>–1</sup> at 713 K, are determined.
The Arrhenius parameters are determined with the pre-exponential factor <i>A</i> = 6.22 × 10<sup>20</sup> h<sup>–1</sup> and
the activation energy <i>E</i><sub>a</sub> = 293 kJ·mol<sup>–1</sup>. Compared with four typical hydrocarbon compounds,
the thermal stability trend is observed in the order of <i>n</i>-dodecane ≈ 1,3,5-triisopropylcyclohexane > bicyclohexyl
> <i>n</i>-propylcyclohexane > decalin. Cyclohexane
and cyclohexene
are found to be the primary products due to the relatively low energy
of the C–C bond connecting the two cyclohexyl rings. Bicyclohexyl
decomposes into cyclohexane and cyclohexene equivalently at the beginning
of the reaction. A probable mechanism on the basis of quantum calculation
and GC-MS analyses for the decomposition of bicyclohexyl is proposed
to explain the product distribution. It is shown that the formation
of decomposition products is mainly obtained through hydrogen transfer, β-scission,
isomerization, or dehydrogenation