Mixed Matrix Membranes

eva marand弗吉尼亚理工学院和州立大学混合基质膜的发展摘要膜分离代表了一个不断发展的技术领域，由于低能源需求和膜模块化设计易于扩大，具有潜在的高经济回报。膜技术的进步，特别是新型膜材料的进步，将使该技术与传统的、高能耗的、昂贵的工艺（如低温蒸馏和吸附）相比更具竞争力。特别是需要大规模的气体分离膜系统，它可以完成氮和氧的富集、氢的回收、天然气中酸性气体（CO2、H2S）的去除、温室气体的捕获以及各种碳氢化合物混合物的分离等过程。在这些应用中使用的材料必须提供耐用性、生产率和高度选择性分离性能，如果它们在经济上可行的话。目前，聚合物和某些无机膜是唯一的候选材料，这两类材料都有局限性。本研究的目标是开发结构复合沸石/聚酰亚胺薄膜，该薄膜将表现出优于现有聚合物基膜的气体分离性能，并且与无机膜相比，将保留其加工多功能性和坚固性。本研究将ETS-4、ZSM-2、LTL和MFI等各向异性板状分子筛应用于混合基质膜中。这些分子筛具有可控的纳米级尺寸分布和表面功能化。混合基质材料的成功在于消除了分子筛/聚合物界面上的缺陷，并在亚纳米水平上控制了薄膜的微观结构。这可以通过使用具有功能化表面的沸石纳米颗粒来促进与聚合物基体的结合来实现。以羧基悬垂官能团作为膜基质，制备了一系列表征良好的新型聚酰亚胺。这些聚酰亚胺已经对各种气体混合物具有优异的分离性能，并且在空气中温度高于400℃时热稳定。通过在聚酰亚胺链和功能化沸石纳米颗粒之间形成氢键或直接共价键，实现了无缺陷的聚合物-沸石界面。

CTS-0107488Eva MarandVirginia Polytechnic Institute and State UniversityThe Development of Mixed-Matrix MembranesAbstractMembrane separations represent a growing technological area with potentially high economic reward due to low energy requirements and facile scale-up of membrane modular design. Advances in membrane technology, especially in novel membrane materials, will make this technology even more competitive with traditional, highly energy-intensive, and costly processes such as low-temperature distillation and adsorption. In particular, there is need for large-scale gas-separation-membrane systems that can accomplish processes such as nitrogen and oxygen enrichment, hydrogen recovery, acid gas (CO2, H2S) removal from natural gas, and capture of greenhouse gases as well as separation of various hydrocarbon mixtures. Materials employed in these applications must offer durability, productivity, and highly selective separation performance if they are to be economically viable. Currently, polymers and certain inorganic membranes are the only candidates, and each of these two classes has limitations.The goal of this research is to develop structured composite zeolite/polyimide thin-film membranes that will exhibit gas-separation performance superior to that of existing polymer-based membranes and which will retain their processing versatility and ruggedness compared to inorganic membranes. This work incorporates anisotropic ETS-4, ZSM-2, LTL and MFI plate-like molecular sieves in mixed-matrix membranes. These zeolites can be produced with controlled nanometer-scale size distribution and surface functionalization. The success of the mixed-matrix materials lies in the elimination of defects at the molecular sieve/polymer interface and in the control of the film's microstructure at the sub-nanometer level. This can be achieved by employing zeolite nanoparticles with functionalized surfaces to promote bonding with the polymer matrix. A series of new, well-characterized polyimides has been developed with pendant carboxylic functional groups to serve as the membrane matrix. These polyimides already have excellent separation properties for various gas mixtures and are thermally stable above 400oC in air. A defect-free polymer-zeolite interface is achieved by forming hydrogen bonds or direct covalent linkages between the polyimide chains and the functionalized zeolite nano-particles.