Mixed Matrix Membranes

CTS-0107488 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是一个不断发展的技术领域，由于膜模块设计的低能量需求和易于放大，具有潜在的高经济效益。膜技术的进步，特别是新型膜材料的发展，将使该技术与传统的、高能源密集型和昂贵的工艺(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，能够完成诸如富氮富氧、氢回收、从天然气中去除酸性气体(二氧化碳、硫化氢)、捕获温室气体以及分离各种碳氢化合物混合物等过程。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的分离性能，才能在经济上可行。目前，聚合物和某些无机膜是唯一的候选材料，这两类膜都有局限性。本研究的目标是开发出具有比现有聚合物基膜更好的气体分离性能，并保持其加工通用性和与无机膜相比坚固耐用的结构化复合沸石/聚酰亚胺薄膜。本工作将各向异性的ETS-4、ZSM-2、LTL和MFI板状分子筛引入混合基质膜中。这些沸石可以通过控制纳米级的粒度分布和表面官能化来制备。混合基质材料的成功之处在于消除了分子筛/聚合物界面的缺陷，并将薄膜的微观结构控制在亚纳米级。这可以通过使用带有功能化表面的沸石纳米颗粒来促进与聚合物基质的结合来实现。一系列新的、表征良好的聚酰亚胺已被开发出来，其中含有侧基的羧基作为膜基质。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，并且在空气中的热稳定性高于400oC。通过在聚酰亚胺链和官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.