ABSTRACT

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.

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