基于分子反应动力学模拟的六甲基二硅氧烷热解机理研究  

Study on pyrolysis mechanism of hexamethyldisiloxane using reactive molecular dynamics simulations

作　　者：陈玉弓 陈昊 黄耀松 CHEN Yugong;CHEN Hao;HUANG Yaosong(College of Energy,Soochow University,Suzhou 215006,Jiangsu,China)

机构地区：[1]苏州大学能源学院,江苏苏州215006

出　　处：《化工学报》2022年第7期2844-2857,共14页CIESC Journal

基　　金：国家自然科学基金项目(52006153)。

摘　　要：六甲基二硅氧烷是燃烧合成高纯二氧化硅纳米颗粒的重要前体,采用ReaxFF分子动力学模拟方法研究其高温热解过程,讨论了三种不同反应力场对模拟的影响并分析其可靠性,选择其中最合适的力场开展不同温度与压力下的热解产物分析,结合气相色谱实验,揭示六甲基二硅氧烷的热解路径和机理。结果表明,反应力场对ReaxFF分子动力学模拟有重要影响,通过比较分析获得了最佳反应力场,六甲基二硅氧烷的初始热解反应为Si—C键断裂导致的CH_(3)脱离,温度升高会加剧解热反应的发生且使产物趋向于碎片化,热解的主要产物为CH_(3)、CH_(4)、C_(2)烃、H_(2)、CH_(2)O等小分子以及SiH_(4)、SiH_(2)、CH_(4)Si等含硅化合物。压力的改变会造成热解体系浓度的改变,从而影响分子间相互碰撞概率和反应的发生,压力越大则越容易形成稳定的热解产物。Hexamethyldisiloxane(HMDSO)is an important precursor for the combustion synthesis of high-purity silica nanoparticles.The pyrolysis of hexamethyldisiloxane was investigated in this work by using ReaxFF reactive molecular dynamics simulations.The effects of three different reaction force fields on the simulations are evaluated and the reliability of each force field is analyzed.The most suitable force field was selected to investigate the pyrolysis products at different temperatures and pressures.The simulation results were used to reveal the pyrolysis path and mechanism of hexamethyldisiloxane together with the gas chromatography experiments.The results show that the reaction force field has important influences on the results of ReaxFF molecular dynamics simulations and the optimal reaction force field is obtained through the comparative analysis.The initial reaction step for HMDSO pyrolysis is the removal of CH_(3)radical induced by Si-C bond breaking.Temperature is a major factor affecting the pyrolysis of HMDSO.The total molecular number of pyrolysis products increases with the temperature increasing and the products tended to be fragmented.The small hydrocarbon molecules(i.e.,CH_(3),CH_(4),C_(2) hydrocarbons,H_(2),CH_(2)O,etc.)and Si-containing products(i.e.,SiH_(4),SiH_(2),CH_(4)Si,etc.)appear in the middle and last stages of the pyrolysis process.The change of pressure will cause the change of the concentration of the pyrolysis system,thus affecting the probability of intermolecular collision and the occurrence of the reaction.The higher the pressure,the easier it is to form a stable pyrolysis product.

关 键 词：六甲基二硅氧烷 热解 反应力场 反应动力学模拟 气相色谱 

分 类 号：O643.12[理学—物理化学] O627.41[理学—化学]