机械互锁结构复合膜的制备及气体分离性能研究

The critical issue in polymeric membranes for biogas separation, the strategy of fabrication highly permeability, anti-plasticization and high CO2/CH4 selectivity membranes, will be investigated. Polymers of intrinsic microporosity (PIMs) possess excellent gas permeability, but they show low anti-plasticization properties when separation biogas that contained acidic gases, resulting in reduced selectivity. In this study, we are planning to prepare high performance biogas separation membranes from designing of membrane materials and structures. PIM-1 and PIM-Trip-TB, two of the best gas permeable membranes of PIMs, are selected to optimize their anti-plasticization and physical aging properties. In this study, a newly three-dimensional porous polymer networks (PPN) will be introduced into PIMs by in-situ polymerization, and a new structure of PIMs and PPN is formed to enhance both the anti-plasticization and physical aging properties. The mechanical interlocking structure formed by non-covalent bonds with PIMs and PPN can solve the anti-plasticization problems caused by molecular chain sliding and physical aging problems caused by molecular chain coiling. The relationship between the chemical structure and gas separation performance of PIMs/PPN composite membranes was systematically studied. The structure and performance of the composite membranes will be optimized by adjusting the pore size, content, molecular weight and reaction conditions of PPN. The effect of composite membranes with different structures on gas molecular mass transfer behavior will be studied. It will provide a theoretical basis of the design of stable and efficient gas separation membrane structure.

本课题针对高分子膜分离生物气的核心问题，即围绕如何制备高渗透性、耐溶胀及高CO2/CH4选择性的气体分离膜进行研究。自具微孔高分子（PIMs）膜具有优异的气体渗透性，但在分离生物气时易被酸性气体溶胀导致选择性降低。本项目拟从膜材料和膜结构设计出发，选用气体渗透性最优的PIM-1和PIM-Trip-TB对其耐溶胀及抗老化性能进行优化研究，设计一种增强膜稳定性的新结构。PIMs从聚合物和单体两种尺寸出发，通过原位合成引入一种三维多孔网状聚合物（PPN），PIMs与PPN之间通过非共价键形成的机械互锁结构可解决由于线性分子链滑动引起的溶胀和分子链卷取引起的老化问题。系统研究PIMs/PPN复合膜的结构与气体分离性能的关系，通过调控PPN孔大小、含量、分子量及反应条件来优化复合膜的结构及性能，研究不同结构复合膜对气体分子传质行为的影响。为稳定高效的气体分离膜结构设计提供理论基础。

本项目针对聚合物气体分离膜易老化、易溶胀的核心问题，对两类最具扩大应用前景的聚合物自具微孔高分子(PIM-1)和聚酰亚胺(PI)膜通过后处理法进行结构调控，制备了高渗透性、耐溶胀及高CO2/CH4选择性的气体分离膜。首先，系统研究了甲磺酸及其甲磺酸/水混合溶液分别对PIM-1结构中腈基转化为酰胺和羧基的影响，阐明了腈基水解过程中基团的变化过程，制得了具有优异气体分离性能的CPIM膜。接着，研究了在空气中加热甲磺酸能够同时水解和交联PIM-1的腈基，形成含羧酸和三嗪基团交联的cPIM-1，同时催化PIM-1基质中多孔聚合物网络(PPN)的原位合成，通过FTIR、XPS、和1H NMR等结构表征证明了此三种反应可通过一步法同时发生。交联和水解过程可以提高cPIM-1的气体选择性，而cPIM-1/PPNs膜的气体渗透性可以通过引入PPNs微结构网络来增加。结果表明：cPIM-1/PPNs对CO2/CH4和CO2/N2的分离性能超过了Roberson 2008上限。其次，研究了热氧化交联的后处理方式对酚酞基聚酰亚胺膜结构-气体分离性能的影响。设计并合成了三种不同结构的酚酞基二胺，并分别与3,3’,4,4’-二苯甲酮四羧酸二酐(BTDA)反应，制备了基于酚酞基的聚酰亚胺。对三种PI膜分别在400℃和425℃下通过热氧化交联进行后处理；内酯环发生分解，同时酰亚胺环打开同时产生多个热交联位点，提高了交联效率，研究发现BTDA-FPP-425的CO2渗透率为170.3 Barrer、CO2/CH4的选择性为37.68。本项目执行过程中在国外重要学术刊物上发表标注项目号的SCI论文9篇，授权发明专利2项；培养研究生2名。本项目的研究为稳定高效的气体分离膜结构设计提供理论基础。