(195e) Scalable and Ultra-Selective Carbon Molecular Sieve (CMS) Membranes for Challenging Gas Separations

Scalable
and Ultra-Selective Carbon Molecular Sieve (CMS) Membranes for Challenging Gas
Separations

Chen Zhang, William J. Koros

School of Chemical and Biomolecular Engineering,
Georgia Institute of Technology, Atlanta, GA

Carbon
molecular sieve (CMS) membranes have received increasing attention in the past
years for advanced gas separations. CMS membranes can be formed into asymmetric
hollow fibers, by controlled pyrolysis of polymeric precursor hollow fiber
membranes, and are capable of delivering simultaneously attractive productivity
and separation efficiency without compromising scalability. Pyrolysis
temperature is among the parameters that control CMS membrane's ultramicropore size
distribution and therefore, gas separation performance. In general, more
densely packed sp²-hybridized graphene-like sheets with lower
permeability and higher selectivity are obtained with increasing pyrolysis
temperature. For example, previous studies¹
showed that CO₂/CH₄ selectivity of Matrimid^®-derived
CMS membranes was enhanced by 200% as pyrolysis temperature increased from 650 ^oC
to 800 ^oC.

Nevertheless,
formation of CMS membranes at pyrolysis temperatures above 800 ^oC
has been rarely reported. This was partially due to challenges involved with processing
brittle CMS dense films. We have discovered that this challenge can be successfully
overcome by using hollow fiber precursors instead of dense film precursors.
This talk will present CMS hollow fiber membranes formed at pyrolysis
temperatures above 800 ^oC. Gas permeation measurements suggested
that these CMS hollow fiber membranes were capable of delivering superior selectivities
that are well-above the polymer upper bound.

References:

1.            (a)
Bhuwania, N.; Labreche, Y.; Achoundong, C. S. K.; Baltazar, J.; Burgess, S. K.;
Karwa, S.; Xu, L.; Henderson, C. L.; Williams, P. J.; Koros, W. J., Engineering
substructure morphology of asymmetric carbon molecular sieve hollow fiber
membranes. Carbon 2014, 76 (0), 417-434; (b) Ning, X.; Koros, W. J., Carbon molecular sieve membranes
derived from Matrimid® polyimide for nitrogen/methane separation. Carbon 2014,
66 (0), 511-522.