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CO2/CH4/N2在MER型沸石中扩散和分离的分子动力学模拟

石勤

石勤. CO2/CH4/N2在MER型沸石中扩散和分离的分子动力学模拟[J]. 燃料化学学报. doi: 10.1016/S1872-5813(21)60095-6
引用本文: 石勤. CO2/CH4/N2在MER型沸石中扩散和分离的分子动力学模拟[J]. 燃料化学学报. doi: 10.1016/S1872-5813(21)60095-6
SHI Qin. Molecular dynamics simulation of diffusion and separation of CO2/CH4/N2 on MER zeolites[J]. Journal of Fuel Chemistry and Technology. doi: 10.1016/S1872-5813(21)60095-6
Citation: SHI Qin. Molecular dynamics simulation of diffusion and separation of CO2/CH4/N2 on MER zeolites[J]. Journal of Fuel Chemistry and Technology. doi: 10.1016/S1872-5813(21)60095-6

CO2/CH4/N2在MER型沸石中扩散和分离的分子动力学模拟

doi: 10.1016/S1872-5813(21)60095-6
基金项目: 甘肃省高等学校创新基金项目(2021B-390)
详细信息
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    Tel: 13919793232, E-mail: 877415710@qq.com

  • 中图分类号: TQ021.4

Molecular dynamics simulation of diffusion and separation of CO2/CH4/N2 on MER zeolites

Funds: The project was supported by Innovation Fund of Colleges and Universities of Gansu (2021B-390)
  • 摘要: 采用巨正则蒙特卡洛(GCMC)模拟方法研究了CO2、CH4和N2在MER型沸石中的吸附性能,模拟结果与实验结果吻合证明模型和力场是可靠的。在此基础上,以纯硅MER型沸石作为对照,采用分子动力学(MD)模拟方法研究了CO2、CH4和N2在K-MER型沸石中的扩散和分离性能。结果表明,CO2、CH4和N2在MER型沸石中存在亚扩散现象,扩散方式为构型扩散,在沸石三维通道中的扩散存在各向异性。沸石与气体之间的作用力和沸石骨架外阳离子均影响气体分子的扩散能力,而沸石骨架外阳离子是影响气体分子扩散能力的主要因素。CO2和N2的自扩散系数随吸附浓度的增加而减小;CH4的自扩散系数随吸附浓度的增大先增加后减小。CO2、CH4和N2的自扩散系数随温度的升高均增加,扩散活化能大小顺序为N2 (16.51 kJ/mol) > CH4(8.39 kJ/mol) > CO2 (4.38 kJ/mol)。K-MER型沸石膜对CO2/CH4、CO2/N2和N2/CH4分离体系均有良好的分离选择性。气体分子的渗透率~104 GPU(1 GPU = 3.35 × 10−10 mol/(s/m2/Pa))。
  • 图  1  混合气体分离模型

    Figure  1  Schematic diagram of mixed gas in separation model

    图  2  不同模拟时间下N2在纯硅MER型沸石中的MSD与时间的关系

    Figure  2  MSD of N2 on silicon MER zeolite versus time at different simulated time at 298 K

    图  3  CO2、CH4和N2在K-MER与纯硅MER型沸石中的吸附等温线

    Figure  3  Adsorption isotherms for CO2, CH4 and N2 on K-MER and silicon MER zeolites at 298 K

    图  4  CO2、CH4和N2在K-MER与纯硅MER型沸石中的等量吸附热

    Figure  4  Adsorption heat for CO2, CH4 and N2 on K-MER and silicon MER zeolites at 298 K

    图  5  CO2、CH4和N2在纯硅MER(a)与K-MER(b)型沸石中的均方位移与时间的关系

    Figure  5  MSD of CO2, CH4 and N2 on silicon MER (a) and K-MER (b) zeolites versus time at 298 K

    图  6  纯硅MER型沸石八元环窗口孔径

    Figure  6  Octet ring window aperture of silicon MER zeolite

    图  7  K-MER型沸石骨架原子与骨架外K+之间的径向分布函数

    Figure  7  Radial distribution function between the framework atoms and extra-framework K+ of K-MER zeolite

    图  8  CO2、CH4和N2在K-MER型沸石中自扩散系数与浓度的关系

    Figure  8  Loading dependence of self-diffusion coefficients for CO2, CH4 and N2 on K-MER zeolites at 298 K

    图  9  CO2、CH4和N2在K-MER型沸石中自扩散系数与温度的关系

    Figure  9  Temperature dependence of self-diffusion coefficients for CO2, CH4 and N2 on K-MER zeolites

    图  10  穿透分子数随时间的变化

    Figure  10  Number of permeation molecules versus time

    图  11  MD模拟5 ns后混合气体穿过沸石膜的快照

    Figure  11  Snapshot of mixed gas permeating through zeolite membrane after a MD simulation time of 5 ns

    表  1  CO2、CH4和N2在MER型沸石中的自扩散系数

    Table  1  Self-diffusion coefficient of CO2, CH4 and N2 on MER zeolites at 298 K

    AdsorbateDSi-MER/(10−12·m2·s−1)DK-MER/(10−12·m2·s−1)
    totalxyztotalxyz
    CO2132.1822.453.40106.1812.376.101.784.48
    CH4170.9200170.922.152.1500
    N2218.1828.2818.70171.185.905.7500.10
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  • 收稿日期:  2021-03-11
  • 修回日期:  2021-04-14
  • 网络出版日期:  2021-05-17

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