新型优先吸附乙烷的柱撑式双配体MOFs材料及增强乙烷乙烯吸附分离机制

In petrochemical industries, ethylene-ethane separation is typically carried out by cryogenic distillation, which is an energy-intensive and capital-intensive process. Developing an effective ethylene–ethane separation technology under ambient conditions is a challenging and valuable research subject. The proposal aims at the development of ethane-trapping pillared-layer MOFs with high ethylene-ethane uptake and selectivity. In this proposed research, we will focus on (I) Fundamental understanding of the effects of the topology structure, surface.properties of pillared-layer MOFs on its adsorption capacity, kinetics, and selectivity for ethylene-ethane mixture. Specially, tuning the topology structure of pillared-layer MOFs and hydrogen bonding forces to enhance their separation performance on the ethylene-ethane mixture. (II) Investigating the effects of ligand components on the topology structure and surface properties of pillared-layer MOFs, and developing novel pillared-layer MOFs with high ethylene-ethane adsorption capacity and selectivity; (III) Investigating the dynamic separation performance of pillared-layer MOFs for ethylene-ethane adsorption separation, modeling and optimizing the adsorption separation process of ethylene-ethane. The proposed work will develop a highly efficient ethylene-ethane separation technology based on novel pillared-layer MOFs. In the aspect of industrial application, it will provide new theories and technologies for efficient separation of ethylene-ethane.

针对石油化工高压低温精馏法分离乙烯乙烷存在高能耗问题，研发常温高效分离乙烯/乙烷技术是一个极具挑战和应用价值的课题。本项目主要研究具有优先吸附乙烷特性、高选择性和高吸附容量的新型柱撑式双配体MOFs材料及乙烯/乙烷吸附分离机制，这是项目特色和重要创新之处。主要涉及：理论上研究柱撑式双配体MOFs多孔材料拓扑孔道结构和表面化学对乙烯/乙烷吸附相平衡、动力学和选择性的关系，尤其是其拓扑空间孔道和表面氢键吸附作用力强化乙烯/乙烷选择性作用机制；技术层面上，研究配体组成对柱撑式双配体MOFs孔道结构和表面化学的影响规律，研制出高乙烯/乙烷选择性和吸附容量的分离材料；在分离过程层面，建立以新型柱撑式双配体MOFs为核心的乙烯乙烷吸附分离过程。项目成果有助于发展和形成新的常温高效分离乙烯乙烷技术，从应用层面上为高效吸附分离乙烯乙烷，提供新理论和新技术基础。

针对石油化工高压低温精馏法分离乙烯乙烷存在高能耗问题，研发常温高效分离乙烯/乙烷技术是一个极具挑战和应用价值的课题。本项目主要研究具有优先吸附乙烷特性、高选择性和高吸附容量的新型柱撑式双配体MOFs材料及乙烯/乙烷吸附分离机制。研究发现：（1）具有“孔笼-孔道-孔笼”结构的铁基PCN-250强化吸附分离C2H6/C2H4的新机制，在298K，1bar条件下，PCN-250多孔材料对C2H6和C2H4的吸附容量分别为5.21和4.22mmol/g。（2）提出一种优先吸附C2H6的铁基MOFs材料对C2H6/C2H4的强化吸附分离策略，即通过增加材料表面金属位点的局部正电性并降低骨架中苯环的电荷密度(低极性的孔道)从而提高铁基MOFs材料对C2H6/C2H4吸附选择性。为了验证这一策略，设计合成了双金属系列PCN-250(Fe2M) (M= Fe, Co, Ni, Zn, Mn) 材料，在298 K和100 kPa时，5种材料的C2H6吸附量均高于绝大多数已报道的优先吸附C2H6的MOFs材料，其中Fe2Zn的C2H6/C2H4选择性最高，为1.7。（3）针对目前大多数分离C2H6/C2H4混合物的材料大多是乙烯选择型吸附剂（更耗能的吸附剂）且材料水汽稳定性差这一问题，提出提高优先吸附乙烷的MOFs材料的水汽稳定性的策略，选择具有高金属-配体键强度，高金属配位数，高的骨架穿插程度，高孔道疏水性并且含低密度不饱和金属位点的材料。最后，综述了C2H6吸附容量、C2H6/C2H4吸附选择性、稳定性、成本、放大合成、再生性能和 材料成型，总结了提高 MOFs对C2H6吸附容量、C2H6/C2H4吸附选择性和水汽稳定性的设计策略，分析优先吸附C2H6吸附材料在吸附分离乙烷和乙烯的挑战和未来发展。项目成果有助于发展和形成新的常温高效分离乙烯乙烷技术，从应用层面上为高效吸附分离乙烯乙烷，提供新理论和新技术基础。