6FDA-DETDA: DABE polyimide-derived carbon molecular sieve hollow fiber membranes: Circumventing unusual aging phenomena

Journal Article · Tue Oct 10 00:00:00 EDT 2017 · Journal of Membrane Science

DOI:https://doi.org/10.1016/j.memsci.2017.10.020· OSTI ID:1594549

Kamath, Manjeshwar G. ^[1]; Fu, Shilu ^[1]; Itta, Arun K. ^[1]; Qiu, Wulin ^[1]; Liu, Gongping ^[1]; Swaidan, Raja ^[2]; Koros, William J. ^[1]

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1. Georgia Institute of Technology, Atlanta, GA (United States)
2. Delaware Research and Technology Center, Newark, DE (United States)

Transport properties are discussed for asymmetric carbon molecular sieve (CMS) hollow fiber membranes based on polyimide precursors derived from a butanol esterified diamino benzoic acid (DABA) based polyimide, 6FDA-DETDA:DABE. Precursor fiber pretreatment with 10% Ethenyl(trimethoxy)silane [vinyltrimethoxysilane (VTMS)] solution in hexane followed by pyrolysis at 550 °C in ultra-high purity argon created asymmetric CMS fibers with CO₂ permeance above 1000 GPU and CO₂/CH₄ selectivities > 25. Storage of the as-made modules for 72 days in 7 bar CO₂ suppressed undesirable aging typically seen under vacuum or atmospheric pressure air and provided CO₂ permeance and CO₂/CH₄ selectivity of 780 GPU and 48 respectively. These results are in contrast to significant losses in CO₂ permeance and CO₂/CH₄ selectivity for CMS created under equivalent pyrolysis conditions from non-esterified 6FDA-DETDA: DABA variant, even under CO₂ storage. The 6FDA-DETDA: DABA-derived CMS results were surprising, since dense film CMS samples from the same precursors did not show the undesirable permeance and selectivity changes. Moreover, other non-DABA containing precursors in dense film and asymmetric fiber forms can be effectively stabilized under CO₂ storage. Such findings suggest that high residual stress in the freshly formed thin selective layers of asymmetric structures in DABA-derived CMS causes undesirable micro-scale rearrangements. In dense films and even asymmetric skins of non-DABA derived CMS membranes, evidence of such undesirable rearrangements are not apparent. DABA-derived cross-links are presumably the cause of these effects. Mono-esterification of 6FDA-DETDA: DABA to form 6FDA-DETDA: DABE controls such crosslinking-derived stresses and resultant instabilities in the CMS fibers, thereby providing stable high performance gas separation properties under CO₂ storage or use in mixed gas feeds.

• Research Organization: Georgia Institute of Technology, Atlanta, GA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: FG02-04ER15510
• OSTI ID: 1594549
• Alternate ID(s): OSTI ID: 1549346
• Journal Information: Journal of Membrane Science, Vol. 546, Issue C; ISSN 0376-7388
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
03 NATURAL GAS
gas separation
carbon molecular sieve membrane
pyrolysis
crosslinking
physical aging