CAREER: A New Paradigm for Creating Silica Membranes from Polymer Hollow Fiber Templates

碳氢化合物是生产燃料和化学品的重要前体，但碳氢化合物的分子形式决定了它作为化学原料的价值。碳氢化合物以同分异构体的形式存在，这是一种化学式相同但原子排列和化学性质不同的化合物。碳氢化合物同分异构体在用作燃料或化学原料之前通常必须分离。然而，同分异构体的分子相似性使它们的分离变得复杂，这传统上是通过能量密集型蒸馏完成的。这些类型的分离的可持续性可以通过在过程中加入膜分离步骤而得到改善。二氧化硅膜可以潜在地提供类似大小的碳氢化合物异构体的快速和选择性运输。然而，硅管或薄膜是脆性的，并且具有大规模使用的挑战性。受光学玻璃细纤维优异的柔韧性的启发，该项目将开发二氧化硅中空细纤维膜，以提供分离性能和可扩展性。这项研究将推动高性能二氧化硅和其他无机膜分离碳氢化合物异构体的极限。使用基于膜的方法分离碳氢化合物异构体的能力将大大减少化学和能源工业产生的温室气体排放。利用实验室对先进膜制造的独特可达性，教育活动将扩大高中学生对膜和可持续分离研究的参与，这些学生来自代表性不足的群体。教育活动的核心是远程推广计划，为上学机会有限的当地高中生提供动手科学体验。该项目旨在利用新型聚合物模板无机中空细纤维衬底，在中等温度下制造出具有可调丁烷异构体传输性能的可扩展二氧化硅膜。超微孔二氧化硅薄膜将用于结构和输运表征。无机中空细纤维基底将由聚合物中空纤维模板衍生而来。采用一种新的牺牲层方法制备二氧化硅中空细纤维膜。动力学吸附测量将补充膜渗透研究，将膜运输特性与二氧化硅超微孔结构联系起来。研究活动将促进对(1)有机烷氧基硅烷化学与超微孔二氧化硅输运性质之间的结构-性能关系的理解；（ii）熵扩散选择性在超微孔二氧化硅分子分化中的作用；（三）可伸缩聚合物模板无机中空细纤维基板的形成机理；（四）牺牲层法制备二氧化硅空心细纤维膜所需的关键部件。获得的新知识将能够在分子和器件水平上操纵二氧化硅膜的特性，为有效的化学分离提供有吸引力和可调的传输特性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Hydrocarbons are important precursors in the production of fuels and chemicals, but the molecular form of the hydrocarbon determines its value as a chemical feedstock. Hydrocarbons exist as isomers, which are compounds that have identical chemical formulas but different atomic arrangements and chemical properties. Hydrocarbon isomers must often be separated prior to their use as fuels or chemical feedstocks. However, the molecular similarity of isomers complicates their separation, which is traditionally accomplished by energy-intensive distillation. The sustainability of these types of separations can be improved upon by including a membrane separation step in the process. Silica membranes can potentially provide rapid and selective transport of similarly sized hydrocarbon isomers. Silica tube or film membranes, however, are brittle and challenging to use at large scale. Inspired by the excellent flexibility of optical glass fine fibers, this project will develop silica hollow fine fiber membranes to provide both separation performance and scalability. The research will push the limits of high-performance silica and other inorganic membranes for hydrocarbon isomer separations and beyond. The ability to separate hydrocarbon isomers using a membrane-based approach will substantially reduce greenhouse gas emissions produced by the chemical and energy industries. Leveraging the lab’s unique accessibility to advanced membrane manufacturing, the education activities will broaden the participation of high school students from underrepresented groups in membrane and sustainable separations research. At the core of the educational activities is a distance outreach program that provides hands-on science experiences to local high school students with limited school access.This project aims to create scalable silica membranes with tunable butane isomer transport properties using novel polymer-templated inorganic hollow fine fiber substrates inexpensively made at moderate temperatures. Ultramicroporous silica films will be made for structural and transport characterizations. Inorganic hollow fine fiber substrates will be derived from polymer hollow fiber templates. Silica hollow fine fiber membranes will be formed by a novel sacrificial layer approach. Kinetic adsorption measurements will complement membrane permeation studies to link membrane transport properties with silica ultramicropore structures. The research activities will advance the understanding of (i) the structure-property relationships between organoalkoxysilane chemistry and ultramicroporous silica transport properties; (ii) the role of entropic diffusion selectivities in molecular differentiation by ultramicroporous silica; (iii) the formation mechanism of scalable polymer-templated inorganic hollow fine fiber substrates; (iv) the key components required to fabricate silica hollow fine fiber membranes by the sacrificial layer approach. The obtained new knowledge will enable the manipulation of silica membrane properties at both molecular and device levels to provide attractive and tunable transport properties for efficient chemical separations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.