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Ultraselective Carbon Molecular Sieve Membranes with Tailored Synergistic Sorption Selective Properties
Author(s) -
Zhang Chen,
Koros William J.
Publication year - 2017
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201701631
Subject(s) - membrane , sorption , permeation , chemical engineering , materials science , molecular sieve , nanoporous , polymer , molecule , carbon fibers , polymer chemistry , organic chemistry , chemistry , nanotechnology , adsorption , composite material , biochemistry , composite number , engineering
Membrane‐based separations can reduce the energy consumption and the CO 2 footprint of large‐scale fluid separations, which are traditionally practiced by energy‐intensive thermally driven processes. Here, a new type of membrane structure based on nanoporous carbon is reported, which, according to this study, is best referred to as carbon/carbon mixed‐matrix (CCMM) membranes. The CCMM membranes are formed by high‐temperature (up to 900 °C) pyrolysis of polyimide precursor hollow‐fiber membranes. Unprecedentedly high permselectivities are seen in CCMM membranes for CO 2 /CH 4 , N 2 /CH 4 , He/CH 4 , and H 2 /CH 4 separations. Analysis of permeation data suggests that the ultrahigh selectivities result from substantially increased sorption selectivities, which is hypothetically owing to the formation of ultraselective micropores that selectively exclude the bulkier CH 4 molecules. With tunable sorption selectivities, the CCMM membranes outperform flexible polymer membranes and traditional rigid molecular‐sieve membranes. The capability to increase sorption selectivities is a powerful tool to leverage diffusion selectivities, and has opened the door to many challenging and economically important fluid separations that require ultrafine differentiation of closely sized molecules.