CAREER: Atomically Detailed Modeling of Transport through Zeolite

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ABSTRACTProposal Number: CTS-9983647Principal Investigator: David S. ShollInstitution: Carnegie Mellon UniversityTitle: CAREER: Atomically Detailed Modeling of Transport through Zeolite MembranesZeolites are solid, crystalline materials that are permeated by networks of ordered nanometer-scale pores. These pores are approximately the same size as many small molecules. Because molecules adsorbed inside zeolite pores are always in intimate contact with the walls of the pore, the diffusion rates, and adsorption energies of various chemical species can depend strongly on the size, shape, and functionality of the species. These facts have long been exploited in the applications of zeolites to shape-selective catalysis and adsorption-based separations. Recent years have seen dramatic advances in the reliable synthesis of ultra-thin membranes made from zeolite crystals. An important challenge in the continuing development of these membranes is the need for accurate theoretical models of their performance. This project will focus on developing hierarchical models of molecular transport through zeolite membranes that combine detailed atomic-scale simulations with macroscopic nonequilibrium thermodynamic theories. A vital part of this process will be a series of direct comparisons between theoretical predictions from this research and experimental results obtained by experimental collaborators. Zeolite membranes have a number of attractive properties. From a macroscopic point of view, they have excellent thermal, mechanical, and chemical stability. These properties allow zeolite membranes to be used under conditions that are too harsh for traditional membrane materials such as polymers. Microscopically, the atomically ordered pore structure of zeolites means that zeolite membranes can, in principle, be extremely selective even for mixtures of molecules with very similar shapes and sizes. By developing theoretical models that explicitly account for the atomic-scale structure of zeolite pores, this project will develop a framework for computationally screening libraries of zeolite structures to choose membrane materials that optimize throughput and selectivity for a desired chemical separation. In the shorter term, this work will clarify the fundamental microscopic processes that control molecular transport through zeolite membranes and provide insight into selecting efficient operating procedures for existing membranes.