化工学报 ›› 2022, Vol. 73 ›› Issue (7): 2844-2857.doi: 10.11949/0438-1157.20220278

• 热力学 • 上一篇    下一篇

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

陈玉弓(),陈昊,黄耀松()   

  1. 苏州大学能源学院，江苏 苏州 215006
  • 收稿日期:2022-03-01 修回日期:2022-05-09 出版日期:2022-07-05 发布日期:2022-08-01
  • 通讯作者: 黄耀松 E-mail:ygchen@stu.suda.edu.cn;yshuang@suda.edu.cn
  • 作者简介:陈玉弓（1997—），男，硕士研究生，ygchen@stu.suda.edu.cn
  • 基金资助:
    国家自然科学基金项目(52006153)

Study on pyrolysis mechanism of hexamethyldisiloxane using reactive molecular dynamics simulations

Yugong CHEN(),Hao CHEN,Yaosong HUANG()   

  1. College of Energy, Soochow University, Suzhou 215006, Jiangsu, China
  • Received:2022-03-01 Revised:2022-05-09 Published:2022-07-05 Online:2022-08-01
  • Contact: Yaosong HUANG E-mail:ygchen@stu.suda.edu.cn;yshuang@suda.edu.cn

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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CH3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CH3、CH4、C2烃、H2、CH2O等小分子以及SiH4、SiH2、CH4Si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。

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

Abstract:

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 CH3 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., CH3, CH4, C2 hydrocarbons, H2, CH2O, etc.) and Si-containing products (i.e., SiH4, SiH2, CH4Si, 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.

Key words: hexamethyldisiloxane, pyrolysis, reactive force field, reactive molecular dynamics simulations, gas chromatography

中图分类号: 

  • O 643.12

图1

HMDSO分子几何构型"

图2

HMDSO分子热解模拟体系的初始构型"

图3

不同目标温度下模拟初始阶段的温度演化"

图4

不同力场在升温模拟过程中体系HMDSO分子数随时间的变化"

图5

模拟时间为40 ps时力场A (a)、力场B (b)及力场C (c)的体系分子分布"

图6

HMDSO单分子的初始热解反应步"

图7

不同力场条件下主要产物随时间的变化"

图8

不同力场条件下HMDSO模拟结束时体系分子分布"

图9

不同温度下部分主要产物随时间的变化"

图10

不同温度下主要含Si产物随时间的变化"

图11

1800 K与2500 K温度条件模拟体系展示"

图12

不同压力下模拟体系总分子数随时间的变化"

图13

不同压力下模拟体系势能随时间的变化"

图14

不同压力下部分主要产物随时间的变化"

图15

不同压力下主要含Si产物随时间的变化"

图16

不同压力条件下模拟体系分子分布"

表1

气相色谱仪预设化合物名及结构"

Peak entryChemical nameChemical structurePeak entryChemical nameChemical structure
1methane2ethane
3ethylene4propane
5cyclopropane6propylene
7iso-butane8n-butane
91,2-propadiene101-butene
11trans-2-butene122-methylpropene
13iso-pentane14cis-2-butene
15n-pentane161,3-butadiene

图17

温度为700℃、800℃、900℃时HMDSO热解色谱图"

表2

不同温度下ReaxFF MD模拟部分主要烃类产物占总产物分子数的比例"

Chemical namePercentage/%
1600 K1800 K2000 K2500 K
methane3.7049.2148.1919.83
acetylene03.1712.0510.34
ethylene3.707.946.028.62
ethane3.7001.200.86

图18

HMDSO主要热解反应路径"

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