High-performance carbon molecular sieve membranes for ethylene/ethane separation derived from an intrinsically microporous polyimide

Octavio Salinas, Xiaohua Ma, Eric Litwiller, Ingo Pinnau

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

An intrinsically microporous polymer with hydroxyl functionalities, PIM-6FDA-OH, was used as a precursor for various types of carbon molecular sieve (CMS) membranes for ethylene/ethane separation. The pristine polyimide films were heated under controlled N2 atmosphere at different stages from 500 to 800 °C. All CMS samples carbonized above 600 °C surpassed the polymeric ethylene/ethane upper bound. Pure-gas selectivity reached 17.5 for the CMS carbonized at 800 °C with an ethylene permeability of about 10 Barrer at 2 bar and 35 °C, becoming the most selective CMS for ethylene/ethane separation reported to date. As expected, gravimetric sorption experiments showed that all CMS membranes had ethylene/ethane solubility selectivities close to one. The permselectivity increased with increasing pyrolysis temperature due to densification of the micropores in the CMS membranes, leading to enhanced diffusivity selectivity. Mixed-gas tests with a binary 50:50 v/v ethylene/ethane feed showed a decrease in selectivity from 14 to 8.3 as the total feed pressure was increased from 4 to 20 bar. The selectivity drop under mixed-gas conditions was attributed to non-ideal effects: (i) Competitive sorption that reduced the permeability of ethylene and (ii) dilation of the CMS that resulted in an increase in the ethane permeability.
Original languageEnglish (US)
Pages (from-to)115-123
Number of pages9
JournalJournal of Membrane Science
Volume500
DOIs
StatePublished - Nov 18 2015

ASJC Scopus subject areas

  • Biochemistry
  • Filtration and Separation
  • Materials Science(all)
  • Physical and Theoretical Chemistry

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