基于丙烯/丙烷分离的ZIF-8中空纤维膜微结构的调控及其性能的研究

The separation of propylene/propane mixtures is one of the most energy-intensive processes in petrochemical industry. To reduce energy cost, membrane-based processes have been considered as one of viable alternatives. However, the low selectivity and poor stability limit this technique for industrial application of separating propylene/propane mixture. In view of the recent demonstration of effective separation of propylene/propane by zeolitic imidazolate frameworks-8 (ZIF-8) membrane, this project is focus on the preparation of high-quality ZIF-8 membranes on ceramic hollow fiber supports. We will systematically study the effect of synthesis parameters (concentration of seed solution, the composition of the secondary growth solution, and other physical parameters) on the microstructure control of the ZIF-8 membranes, and will explore the possible growth mechanism for ZIF-8 membranes, even ZIFs membranes. At the same time, we also examine how operation parameters and impure gas molecules affect the stability and separation performance of propylene/propane on ZIF-8 membranes, and explore the adsorption and diffusion behavior of propylene, propane and impure gas molecules on ZIF-8 materials. The overall goals of this project are to build the relationship between membrane synthesis parameters and the microstructure of ZIF-8 hollow fiber membranes, and to obtain the optimized operation conditions for the potential application of ZIF-8 membranes on propylene/propane separation.

分离丙烯/丙烷混合气体是目前石油工业中最耗能的过程之一，而膜分离技术被认为是潜在的实现低能耗、低成本分离丙烯/丙烷的主要手段之一。然而，分离选择性低以及稳定性差，成为限制该技术应用于工业分离丙烯/丙烷混合气体的主要瓶颈。鉴于目前沸石咪唑酯骨架材料（ZIF-8）膜能够有效地分离丙烯/丙烷混合气体，本课题拟以在陶瓷中空纤维载体上制备高质量的ZIF-8膜为目标；研究晶种浓度，二次合成液的组成以及合成参数等因素与膜微结构（晶体形貌、晶体间的交互生长、膜厚度等）之间的定量关系，实现对ZIF-8中空纤维膜微结构的调控，并探索二次生长过程中ZIF-8膜在中空纤维载体表面的形成机理。同时也研究操作条件和气体杂质对丙烯/丙烷混合气体分离效果的影响规律，获得膜分离性能调控的手段；为实现其潜在的工业应用提供依据。

本项目针对现有的高能耗分离丙烯/丙烷混合气的低温精馏工艺，提出用金属有机骨架ZIF-8膜为新一代的分子筛材料，在多孔陶瓷支撑体上，开展ZIF-8膜的制备研究。项目实施过程中，紧紧围绕分子筛膜制备的共性技术问题（制备重复性低、易产生缺陷、稳定性差），通过优化膜微结构的形成过程，探索ZIF-8膜的形成机理，有效地提高了ZIF-8膜制备的重复性，提高了丙烯/丙烷的分离选择性，提出了一种采用硅橡胶（PDMS）修复ZIF-8膜缺陷的方法，构建了金属锌盐前驱物与ZIF-8材料水热稳定性的关系。初步形成基于ZIF-8膜分离丙烯/丙烷的分离机理，对潜在的工业分离应用具有积极地指导意义。在Chem. Commun., J. Membrane Sci., Chem. Eng. Sci.等化学化工主流期刊发表SCI论文6篇，申请中国发明专利3项（已公开），参加国内外重要学术会议3次。