Carbon molecular sieve (CMS) membranes have attractive separation performance properties, greatly exceeding an �upper bound� trade-off curve of polymeric membrane performance for many challenging gas separations.  An asymmetric hollow fiber membrane morphology is preferred for such applications due to the ability to form high surface area to volume ratio modules.  Fortunately, CMS fibers appear to have an additional advantage over dense films, since they offer better mechanical strength and flexibility and ability to be handled.  CMS fibers are prepared by pyrolyzing polymer fibers, well above their glass transition temperatures.             In this study, asymmetric hollow fiber precursor membranes were pyrolyzed to create CMS fibers by adapting an oxygen �doping� method previously developed using CMS dense films.  Defect-free asymmetric hollow fibers are spun and used to evaluate efficacy of the CMS membrane production method which involves careful tuning of oxygen concentration during the pyrolysis process.   Mixed gas feed of CO2 and CH4 with high feed pressure are used to characterize these CMS fibers.  The experimental mixed gas separation properties are compared with theoretical values predicted using the single gas permeation and sorption experimental results.  The effect of permeate pressure is also discussed to evaluate high performing CMS fibers under realistic conditions.

Effect of pyrolysis atmosphere on asymmetric hollow fiber carbon molecular sieve membranes

241st National Meeting (2011)

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