摘要/Abstract
常规的烯烃/烷烃冷冻加压精馏分离过程具有高能耗和低效率的特点, 吸附分离技术可以在温和条件下高效纯化烯烃分子而在烯烃/烷烃分离领域展现出广阔应用前景. 本工作采用高通量筛选技术从12723个真实金属-有机骨架(MOF)材料中筛选具有优异C4烯烃混合物选择性吸附性能的吸附剂, 用于1,3-丁二烯的分离纯化. 首先, 根据MOF材料的结构参数进行筛选获得了7681个具有合适孔径和比表面积的吸附剂. 然后, 采用分子力学方法计算出上述吸附剂的力学性能, 以UIO-66力学性能为阈值得到959个结构稳定的候选MOF材料. 接下来采用巨正则蒙特卡洛(GCMC)方法模拟出298 K、0.1 MPa下五元等摩尔C4烯烃混合物在不同候选MOFs中的选择性吸附行为, 根据候选MOFs对1,3-丁二烯的吸附性能分值(APS)进行排序, 得到具有最佳吸附分离性能的8种MOF材料. 通过定量构效关系、吸附等温线及理想吸附溶液理论等揭示了高吸附分离性能MOFs的结构特征, 利用穿透曲线模拟进一步验证了填充最优吸附剂RIGPEE01的固定床能够有效分离2-顺式丁烯/1,3-丁二烯双组分混合物. 最后, 通过径向分布函数和结合能计算分析, 确定RIGPEE01对1,3-丁二烯产生优先吸附的机理主要归因于Cu(I)强吸附位点、π键耦合效应和尺寸筛分效应. 本工作提出的高通量筛选方法以及从分子尺度理解MOF材料应用于烯烃分离机制的视角, 为进一步开发烯烃/烷烃混合物分离的新型吸附剂奠定了理论基础.
关键词: 真实金属-有机骨架材料, 分子模拟, 高通量筛选, 吸附分离, 1,3-丁二烯
The conventional separation process of olefin/paraffin with cryogenic and high-pressure distillation usually exhibits high energy consumption and low efficiency. The adsorption separation technology is widely promising in the field of olefin/paraffin separation because of its mild operation conditions and high energy efficiency. In this work, high-throughput screening was adopted to find the optimal adsorbents from 12723 real metal-organic framework (MOF) materials, which is available for adsorption separation of 1,3-butadiene from C4 olefin/paraffin mixture. Firstly, 7681 adsorbents with suitable pore size and specific surface area were selected from the total database according to their structural parameters. Then their mechanical properties were computed by molecular mechanics. The mechanical properties of UIO-66 were used as the threshold to obtain 959 candidate MOFs with stable structure. Secondly, the grand canonical Monte Carlo (GCMC) simulation was performed to calculate the selective adsorption behavior of a quinary equimolar C4 olefin mixture in different candidate MOFs at 298 K and 0.1 MPa. According to their adsorption performance scores (APS) of 1,3-butadiene, the candidate MOFs are ranked to obtain 8 MOFs with the optimal adsorption and separation performance. The structural characteristics of MOFs with high adsorption and separation performance are revealed through quantitative structure-activity relationship, adsorption isotherm and ideal adsorption solution theory. The breakthrough curve simulation further verified that 2-cis-butene could effectively separate from 1,3-butadiene in the fixed bed filled with the optimal adsorbent RIGPEE01. Finally, it is determined that the preferential adsorption mechanism of 1,3-butadiene in RIGPEE01 is mainly due to the strong adsorption sites of Cu(I), π bond coupling effect and the size sieving effect based on the radial distribution function and binding energy analysis. The high-throughput screening method and the molecule-level insights on the olefin separation mechanism of MOFs proposed in this work have laid a theoretical foundation for the further development of new adsorbents for the separation of olefin/paraffin mixtures.
Key words: real metal-organic framework, molecular simulation, high-throughput screening, adsorption separation, 1,3-butadiene
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