化学反应活性指标与基元反应动力学参数的关系及链烷烃热裂解过程模型

本文采用广义休克尔法(EHMO)与全略微分重叠法(CNDO/2)计算了链烷烃及其自由基的反应活性指标.通过分析已知的基元反应动力学参数与这些指标间的关系,提出一种预测基元反应速率常数的方法.对链烷烃热裂解速度常数的预测,证明该法是可靠的.在此基础上,采用平推流反应器(PFR)模型及拟稳态假设描述C_4~-烃类热裂解过程,模拟了c_4~-单一烃及混合烃的热裂解过程.模拟结果与文献中的总包反应实验数据吻合良好,证明所建模型是正确、可靠的.

A STUDY ON DEPENDENCE OF CHEMICAL REACTIVITYNDICES AND ELEMENTARY REACTION KINETIC PARAMETERSAND MODEL OF THERMAL CRACKING PROCESS OFPARAFFINS

In this paper, Extended Huckel Molecular Orbital Theory (EHMO) and Complete Neglect Differential and Overlap Method (CNDO/2) are used to calculate chemical reactivity indices of paraffins and their radicals. Through analysing the dependence of known elementary reaction rate constants on the chemicl reactivity indices, a method for predicting unknown kinetic rate constants is presented. By means of the method, a relation between kinetic behavior of reactants (macro-properties) and their molecular structural properties (micro -properties) is established. The method is used to predict elementary rate constants of thermal cracking of paraffins and is proved to be feasible and reliable. On this basis, PFR model and pseduo - steady - state assumption are used to describe the thermal cracking process of C4- paraffins. Michelson and pseudo -Newton methods are used to self - consistently solve kinetic differential and algebraic equations. The simulated results have good agreement with overall experimental data published in the literature. It indicates that the established kinetic model of thermal cracking of paraffins is correct and reliable.