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Kinetic modeling for hydrogen-abstraction reaction of methylcyclohexane with the center dot CH3 radical




作者: Guan, Yulei; Yang, Bolun
发表/完成日期: 2012-09-10
期刊名称: CHEMICAL ENGINEERING SCIENCE
期卷: 79
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论文简介
Hybrid density functionals (BMK and MPWB1K) with the CBSB7 and 6-311++G(2df,2p) basis sets were employed to investigate the mechanism and kinetics of the center dot CH3 radical abstracting the primary, secondary, and tertiary H sites within the methylcyclohexane (MCH) molecule. Furthermore, the distinct orientations of H atoms bonded to the same C atom were taken into account. The density functional energetics was also validated against benchmark calculations with the high-level CBS-QB3 method. The kinetic parameters were evaluated using standard transition-state theory with either the Wigner or Eckart tunneling corrections and anharmonic torsion included over a wide temperature range 373-1600 K. These calculated results indicate that the energetic demand for H-abstraction reaction decreases in the tertiary < secondary < primary order. The total rate constant calculated at the MPWB1K/CBSB7 level with the Wigner tunneling correction and torsional modes treated by the Chuang-Truhlar (Cr) method agrees very well with the reported experimental kinetics data. The activation energy for total reaction increases substantially with temperature and exhibits almost linear temperature dependence. The obtained three-parameter Arrhenius expression and the temperature-dependent branching ratio for each reaction channel of center dot CH3+MCH can be extrapolated over the wide temperature range of 373-1600 K.