CIESC Journal ›› 2025, Vol. 76 ›› Issue (5): 2313-2326.DOI: 10.11949/0438-1157.20241314

• Separation engineering • Previous Articles     Next Articles

Molecular simulation study on adsorption and diffusion of C3H6 and C3H8 on Co/Zn-ZIFs

Hao QI1(), Yujie WANG1,2(), Shenhui LI1, Qi ZOU2, Yiqun LIU2, Zhiping ZHAO1()   

  1. 1.School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 102488, China
    2.Sinopec Beijing Research Institute of Chemical Industry, Beijing 100013, China
  • Received:2024-11-18 Revised:2025-01-24 Online:2025-06-13 Published:2025-05-25
  • Contact: Yujie WANG, Zhiping ZHAO

双金属Co/Zn-ZIFs中C3H6和C3H8吸附和扩散行为分子模拟研究

齐昊1(), 王玉杰1,2(), 李申辉1, 邹琦2, 刘轶群2, 赵之平1()   

  1. 1.北京理工大学化学与化工学院,北京 102488
    2.中石化(北京)化工研究院有限公司,北京 100013
  • 通讯作者: 王玉杰,赵之平
  • 作者简介:齐昊(1998—),男,硕士研究生,2765618801@qq.com
  • 基金资助:
    中国石化科技项目(224117)

Abstract:

Based on first-principles calculations, 11 bimetallic organic framework Co/Zn-ZIFs molecular models (1#, 2#, 3#, etc.) were constructed. Each model has the same window structure. The adsorption properties of C3H6 and C3H8 on Co/Zn-ZIFs were studied by the Grand Canonical Monte Carlo method. The adsorption mechanisms of C3H6 and C3H8 on Co/Zn-ZIFs were analyzed by adsorption heat distribution, adsorption sites, weak interactions, electrostatic potential and differential charge density. Molecular dynamics was used to calculate the diffusion characteristics of C3H6 and C3H8 at the windows of Co/Zn-ZIFs. The results indicated that the adsorption of C3H6 and C3H8 on Co/Zn-ZIFs mainly occurs near the imidazole ring and methyl group of the ligands. Within a certain range, increasing the temperature and decreasing the pressure were both beneficial for achieving preferential adsorption of C3H8. At an ambient temperature of 323 K and a pressure of 0.5 bar, the ideal adsorption selectivity of C3H8 to C3H6 for 3# Co/Zn ZIFs is the highest, at 1.25. The diffusion free energy difference between C3H6 and C3H8 is the largest at the 6# Co/Zn-ZIFs windows, which is 14.60 kJ/mol. The self-diffusion coefficients of C3H6 and C3H8 are 3.910×10-10 and 1.445×10-12, respectively. The ideal diffusion selectivity of C3H6/C3H8 was the highest, as high as 270.59. For different Co/Zn-ZIFs molecular models with the same metal ratio have similar C3H6 adsorption capacities and C3H8 adsorption capacities. When the metal atoms with a small proportion are distributed alternately, the diffusion free energy of C3H6 and C3H8 is the highest, and the difference in diffusion free energy between C3H8 and C3H6 increases, thereby improving the separation selectivity of C3H6/C3H8. For Co/Zn-ZIFs molecular models with different metal ratios, they have similar C3H6 adsorption capacities and C3H8 adsorption capacities. As the Co/Zn ratio increases, the diffusion free energies of C3H6 and C3H8 molecules gradually increases, which increases the diffusion resistance of C3H6 and C3H8. These results provided valuable theoretical basis for analyzing the separation of C3H6/C3H8 mixtures by Co/Zn-ZIFs.

Key words: molecular simulation, Co/Zn-ZIFs, C3H6/C3H8, adsorption, diffusion

摘要:

基于第一性原理计算,构建出11种双金属有机框架Co/Zn-ZIFs分子模型(1#、2#、3#等),每一种模型各窗口结构相同,采用巨正则蒙特卡罗的方法研究了C3H6、C3H8分别在Co/Zn-ZIFs上的吸附性能,通过吸附热分布、吸附位点、弱相互作用、静电势及差分电荷密度等方法分析了C3H6、C3H8分别在Co/Zn-ZIFs上吸附机理,并采用分子动力学计算了C3H6、C3H8分别在Co/Zn-ZIFs窗口处的扩散特性。结果表明:C3H6、C3H8在Co/Zn-ZIFs上的吸附主要作用在配体咪唑环与甲基附近;一定范围内,升高温度、降低压力均有利于实现优先吸附C3H8,在环境温度为323 K,环境压力为0.5 bar下,3# Co/Zn-ZIFs的C3H8对C3H6的理想吸附选择性最高,为1.25。C3H6、C3H8在6# Co/Zn-ZIFs窗口处扩散自由能差值最大,为14.60 kJ/mol,C3H6、C3H8自扩散系数分别为3.910×10-10和1.445×10-12,C3H6/C3H8理想扩散选择性最高,为270.59。对于相同金属比例的不同Co/Zn-ZIFs分子模型,具有相近的C3H6吸附量和C3H8吸附量,当占比少的金属原子呈相间分布时,C3H6、C3H8的扩散自由能最大,且C3H8与C3H6的扩散自由能差值变大,从而提升了C3H6/C3H8分离选择性。对于不同金属比例的Co/Zn-ZIFs分子模型,具有相近的C3H6吸附量和C3H8吸附量,随着Co/Zn比例上升,C3H8、C3H6分子的扩散自由能均逐渐增大,扩散阻力增大。结果对分析Co/Zn-ZIFs分离C3H6/C3H8提供了极具价值的理论依据。

关键词: 分子模拟, Co/Zn-ZIFs, C3H6/C3H8, 吸附, 扩散

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