金属改性类石墨烯吸附剂的构建及用于丙烯/丙烷分离的机理研究

Propylene, which is one of the important basic organic chemical raw materials, plays an extremely important role in the national production. However, the traditional propylene/propane distillation separation in the process of propylene production is high energy cost. Compared with traditional systems for gas separation, pressure swing adsorption (PSA) separation is desirable, however, the adsorbent that used for PSA is often lack of high selectivity and high working capacity. This study try to construct novel adsorbent by the combination of open metal site and the graphene-like PTI nanosheet. The selective adsorption of propylene can be improved by the exist of the open metal site, in addition, considered the stability and fast adsorption equilibriumand of the PTI nanosheet, the novel adsorbetn may be a promising candidate for the propylene/propane separation with high efficiency and low energy cost. The feasibility of loading of metal ions on the PTI nanosheet is analyzed, and the role of the metal ions in the gas adsorption and the nature of the difference bwteen the adsorptive selectivity are also explored from the electronic level by the DFT method. In addition, the effect of the interaction between the gas components on the properties of adsorbent is investigated by the molecular simulation. The knowledge obtained in these study may provide useful guidance for future efforts to synthesize novel adsorbent with improved gas separation performance.

丙烯是重要的基础有机化工原料之一，在国民生产中起着极其重要的作用。然而在丙烯生产过程中，传统的丙烯/丙烷精馏分离技术能耗过大。变压吸附分离技术（PSA）具有传统分离技术无可比拟的优点，但缺乏高选择性和高工作容量的吸附剂。本项目提出开放金属位和类石墨烯PTI纳米片协同构建新型吸附剂的思路：通过开放金属位的络合效应提升吸附剂对丙烯的选择性吸附，同时结合PTI纳米片作为吸附剂的稳定性和快速吸附平衡等特点，以达到丙烯/丙烷高效低能耗分离。在研究计划中，拟从理论层面分析PTI纳米片上负载金属离子的可行性，考察金属离子在气体吸附中所扮演的角色；并从电子层面明确吸附剂对气体选择性的本质差异；此外通过分子模拟考察混合气体各组分间的相互作用对吸附剂性能的影响。通过以上的理论研究，以期为丙烯/丙烷的高效分离开辟新思路。

同时具有较高的选择性和吸附量的吸附剂，有望替代传统的丙烯/丙烷(C3H6/C3H8)低温蒸馏分离技术。不饱和金属位(CUS)在烯烃的选择性吸附中起着至关重要的作用。超薄聚三嗪酰亚胺(PTI)纳米片由于其较大的表面体积比，可以快速达到气体吸附平衡。本项目结合CUS和PTI纳米片的优点，将Li CUSs引入到PTI纳米片中，用于C3H6/C3H8分离。密度泛函理论(DFT)计算证明了将Li CUSs引入到PTI纳米薄片的热力学可行性。这些高度暴露的Li CUSs对C3H6比对C3H8具有更高的吸附亲和力。利用DFT-衍生力场参数，我们进一步进行了巨正则蒙特卡洛（GCMC）模拟，研究了C3H6/C3H8在不同孔径(H)Li-PTI配合物狭缝孔模型上的吸附。我们发现在相应条件下，Li-PTI配合物对C3H6/C3H8具有较高的选择性(4.2~7.9)。此外，Li-PTI复合物的裂隙孔具有较大的C3H6工作容量(1.5~4.0mmol/g)，优于大多数已有报道的吸附剂的计算结果。狭缝孔结构的Li-PTI配合物具有作为C3H6/C3H8分离材料的潜力。此外，通过实验合成相关金属负载PTI纳米片，从实验上验证了金属离子与PTI纳米片相结合的可行性，并拓宽了该材料的应用领域。