Tuning carbon molecular sieve membrane performance for challenging gas separations
Wenz, Graham Benjamin
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Membranes are emerging as tools for energy efficient alternatives to thermally-driven phase-changed based gas separations. As direct replacement of traditional separation processes with membrane-based processes is currently not feasible due to the low separation efficiency of current membrane materials, development of advanced membrane materials is of significant interest. Carbon molecular sieve (CMS) membranes have emerged as a new material that can surpass the polymer productivity-selectivity “upper bound”. As CMS membranes are commonly formed by the high temperature pyrolysis of polymeric precursors, they are uniquely situated for translation from lab-scale academic materials, to applications in large-scale industrial gas separation processes. Furthermore, the bimodal pore size distribution present in CMS materials results in an attractive combination of productivity and exquisite size and shape selectivity. However, deeper fundamental knowledge of the complex amorphous CMS microstructure is desired to facilitate directed engineering of separation performance of CMS membranes for challenging gas separations. This work focuses on advancement of the fundamental understanding of CMS membranes by investigation of various formation and post-synthetic treatments and their effects on gas transport. While this work focused on modification of CMS membranes derived from the high performance 6FDA:BPDA-DAM(1:1) polyimide precursor, the framework developed allows for extension to CMS materials derived from different precursors or formation conditions.