EAGER: Towards Development of High Performance Mixed-Matrix-Membrane for Separation Applications

将气体混合物或液体混合物高效且经济地分离为纯组分对于包括石油和天然气、食品、化工和制药在内的各种行业都很重要。膜是一种通过不同分子通过膜孔的能力来分离分子的材料。虽然已经开发了许多气体和液体分离技术，但随着复杂的新材料的开发，膜显示出越来越大的前景。膜技术的一个新兴领域涉及一种特殊类型的膜，称为混合基质膜。（或mm），其中纳米颗粒（直径在几十纳米量级的无机物颗粒）分散在长链分子（也称为聚合物）的基质中。制造mm的挑战包括确保高浓度的纳米颗粒均匀分布在整个聚合物中，并且纳米颗粒牢固地粘附在聚合物分子上。该研究项目结合了新型涂层和材料加工技术，以高浓度均匀分布在mm中，并生产出无缺陷的高性能膜。这一结果将使我们深入了解如何为广泛的应用生产膜，并将使我们更好地理解如何处理纳米颗粒。本研究项目的主要目标是开发一种溶剂热退火工艺，用于生产无缺陷的mm，重点是高通量、可负担得起的技术，使纳米颗粒在聚合物相中具有良好的分散性和强附着力。假设是，在静电纺丝过程中产生的分散静电力产生的纤维垫可以作为采用粉末涂层技术的聚结工艺后的高颗粒分散性和强纳米颗粒-聚合物粘附性的mm的前驱体。其中，分子筛的颗粒相为沸石型咪唑酸盐骨架（ZIF-8），分子筛是一种研究较为成熟的用于气体分离的金属有机骨架（MOF）；分子筛的聚合物相为Matrimid，是一种广泛应用于商业膜的聚酰亚胺。正在探讨的关键基本问题是：(1)静电纺丝过程中纳米颗粒分散的重要机制是什么，以及如何利用它们来最大限度地分散；(2)在溶剂热聚结过程中纤维如何水平进入MATS，以及如何控制这一过程以促进聚合物运输，同时最大限度地减少纳米颗粒之间的吸引力；(3)在保持理论分离和渗透特性的同时，这种技术可以在多大程度上推动负载和薄度。初步实验表明，可以通过逐步增加溶剂与非溶剂的比例来控制纤维的聚结，从而控制纤维的聚结平衡，但其基本现象尚不清楚。本课题的成功完成将对储氢、碳捕获、烃类吸附分离、多相催化等诸多领域产生积极影响。

Efficient and cost-effective separation of mixtures of gases or mixtures of liquids into pure components is important for a variety of industries, including oil and gas, food, chemical, and pharmaceutical.  A membrane is a material that separates molecules via differences in their ability to traverse the pores of the membrane. While many techniques for gas and liquid separations have been developed, membranes have shown increasing promise as sophisticated new materials have been developed.  An emerging field in membrane technology involves a special type of membrane called ?Mixed-Matrix-Membranes? (or MMMs), in which nanoparticles (particles of inorganic matter that have a diameter on the order of tens of nanometers) are dispersed within a matrix of long chain molecules, also known as polymers.  Challenges in making MMMs include insuring that high concentrations of nanoparticles are well distributed throughout the polymer and that the nanoparticles adhere strongly to the polymer molecules.  This research project combines novel coating and materials processing technologies to uniformly distribute the nanoparticles in MMMs at high concentrations and to produce high performance membranes that are free of defects.  The results will yield insights into how to produce membranes for a broad range of applications and will lead to a better understanding of how to process nanoparticles.The main objective of this research project is to develop a solvothermal annealing process for producing defect-free MMMs, with an emphasis on high-throughput affordable techniques that yield both good dispersion and strong adhesion of the nanoparticles in the polymer phase. The hypothesis is that the fibrous mats produced by dispersive electrostatic forces induced during the electrospinning process may be used as a precursor to MMMs with high particle dispersion and strong nanoparticle-polymer adhesion after a coalescing process adapted from powder coating techniques. Specifically, zeolitic imidazolate framework (ZIF-8), a well-studied metal-organic framework (MOF) for gas separations is selected as the particle phase, and Matrimid, a polyimide widely used in commercial membranes, is selected as the polymer phase for the preliminary study. The key fundamental questions that are being explored are: (1) what are the important mechanisms involved in nanoparticle dispersion during electrospinning and how can they be leveraged to maximize dispersion, (2) how do fibers level into mats during solvothermal coalescence and how can this process be controlled to promote polymer transport while minimizing attraction between nanoparticles, and (3) how far can loading and thinness be pushed with this technique while retaining theoretical separation and permeation properties. Preliminary experiments indicate that it is possible to control the coalescence of the fibers by incrementally increasing a solvent to non-solvent ratio, and thus the equilibrium of fiber coalescence, but the underlying phenomena are not well understood. Successful conclusion of this research project will have a positive impact on many fields, such as hydrogen storage, carbon capture, adsorptive separation of hydrocarbons, and heterogeneous catalysis.