2 research outputs found
Ab Initio Investigation of the Thermal Decomposition of <i>n</i>‑Butylcyclohexane
Environmental
and energy security concerns have motivated an increased
focus on developing clean, efficient combustors, which increasingly
relies on insight into the combustion chemistry of fuels. In particular,
naphthenes (cycloalkanes and alkylcycloalkanes) are important chemical
components of distillate fuels, such as diesel and jet fuels. As such,
there is a growing interest in describing napthene reactivity with
kinetic mechanisms. Use of these mechanisms in predictive combustion
models aids in the development of combustors. This study focuses on
the pyrolysis of <i>n</i>-butylcyclohexane (<i>n</i>-BCH), an important representative of naphthenes in jet fuels. Seven
different unimolecular decomposition pathways of C–C bond fission
were explored utilizing ab initio/DFT methods. Accurate reaction energies
were computed using the high-level quantum composite G3B3 method.
Variational transition state theory, Rice–Ramsperger–Kassel–Marcus/master
equation simulations provided temperature- and pressure-dependent
rate constants. Implementation of these pathways into an existing
chemical kinetic mechanism improved the prediction of experimental
OH radical and H<sub>2</sub>O speciation in shock tube oxidation.
Simulations of this combustion showed a change in the expected decomposition
chemistry of <i>n</i>-BCH, predicting increased production
of cyclic alkyl radicals instead of straight-chain alkenes. The most
prominent reaction pathway for the decomposition of <i>n</i>-BCH is <i>n</i>-BCH = C<sub>3</sub>H<sub>7</sub> + C<sub>7</sub>H<sub>13</sub>. The results of this study provide insight
into the combustion of <i>n</i>-BCH and will aid in the
future development of naphthene kinetic mechanisms