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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Pyrolysis of Alkanes: A Computational Approach
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Pyrolysis of Alkanes: A Computational Approach

机译：烷烃的热解：计算方法

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In this study, we investigate the kinetic and thermodynamic aspects of thermal cracking reactions of short paraffin chains by density functional theory (DFT) methods. The thermal cracking reactions have been modeled for a series of shorter unbranched alkanes at 673 K by following a free-radical mechanism. Benchmark calculations have been carried out with different functionals (B3LYP, M06-2X, PBE0, BMK, B3PW91) and basis sets (6-31G(d,p), 6-311+G(d,p)) to determine the most suitable DFT method, and the results were compared to the available experimental data. Computations were also performed at the CBS-QB3 level to evaluate the accuracy of the DFT method. The thermodynamic and kinetic properties of the initiation, hydrogen atom transfer (HAT), and decomposition (beta-scission) reactions are intensely discussed to better understand the trends in product distributions at high temperatures. Evans-Polanyi (EP) relations have been used to build a linear relationship between the enthalpy of reactions and their activation energies; this process may be useful for the determination of the kinetic parameters of longer paraffin chains as well. Finally, the preexponential factors of short-chain paraffin have been calculated and classified based on the identity of the radicalic products. The latter, together with the activation energies derived from the EP relations can be used safely for the prediction of the rate constants for long paraffin chains.
机译：在这项研究中，我们研究了密度泛函理论（DFT）方法的短链烷链链的热裂解反应的动力学和热力学方面。通过以下自由基机制，在673k下为一系列短的未支撑烷烃进行了模拟的热裂化反应。基准计算已采用不同的功能（B3LYP，M06-2X，PBE0，BMK，B3PW91）和基集（6-31G（D，P），6-311 + G（D，P））来确定最多合适的DFT方法，结果与可用的实验数据进行比较。在CBS-QB3级别也执行计算以评估DFT方法的准确性。引发的热力学和动力学性质，氢原子转移（帽子）和分解（β - 易于）反应强烈讨论，以更好地了解高温下产品分布的趋势。埃文斯 - 波兰尼（EP）关系已被用来建立反应焓与其激活能之间的线性关系;该方法可能是用于确定较长石蜡链的动力学参数。最后，基于自由基产品的身份计算和分类了短链石蜡的预先表现因子。后者与来自EP关系的激活能量一起可以安全地用于预测长石蜡链的速率常数。

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