Ethylene/ethane permeation, diffusion and gas sorption properties of carbon molecular sieve membranes derived from the prototype ladder polymer of intrinsic microporosity (PIM-1)

• Published in: Journal of membrane science Vol. 504; pp. 133 - 140
• Main Authors: Salinas, Octavio, Ma, Xiaohua, Litwiller, Eric, Pinnau, Ingo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2016
• Subjects: artificial membranes; Carbon; Carbon molecular sieve; carbonization; crosslinking; Diffusion; dioxane; Ethane; Ethylene; Ethylene/ethane separation; heat treatment; Hydroxyl groups; Intrinsically microporous polymer; Membranes; Microporosity; moieties; Molecular sieves; oxygen; permeability; PIM-1; polymers; prototypes; pyrolysis; sieving; sorption; surface area; temperature; PIM-1; Carbon molecular sieve; Intrinsically microporous polymer; Ethylene/ethane separation
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2015.12.052

Fine-tuning the microporosity of PIM-1 by heat treatment was applied to develop a suitable carbon molecular sieve membrane for ethylene/ethane separation. Pristine PIM-1 films were heated from 400 to 800°C under inert N2 atmosphere (<2ppm O2). At 400°C, PIM-1 self-cross-linked and developed polar carbonyl and hydroxyl groups due to partial dioxane splitting in the polymer backbone. Significant degradation occurred at 600°C due to carbonization of PIM-1 and resulted in 30% increase in cumulative surface area compared to its cross-linked predecessor. In addition, PIM-1-based CMS developed smaller ultramicropores with increasing pyrolysis temperature, which enhanced their molecular sieving capability by restricted diffusion of ethylene and ethane through the matrix due to microstructural carbon densification. Consequently, the pure-gas ethylene permeability (measured at 35°C and 2bar) decreased from 1600Barrer for the pristine PIM-1 to 1.3Barrer for the amorphous carbon generated at 800°C, whereas the ethylene/ethane pure-gas selectivity increased significantly from 1.8 to 13. [Display omitted] •First report of ladder PIM-1-derived CMS membranes for ethylene/ethane separation.•PIM-1-derived CMS (pyrolized at 800°C) shows high pure-gas selectivity (αC2H4/C2H6~13).•Ethylene/ethane permselectivity of the CMS membrane is dominated by diffusivity selectivity.•Intrinsic polymer precursor microporosity appears to have influence on CMS gas permeability.