Title:
Carbon molecular sieve membranes for natural gas separations

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dc.contributor.advisor Koros, William J.
dc.contributor.author Kiyono, Mayumi en_US
dc.contributor.committeeMember P. Jason Williams
dc.contributor.committeeMember Ronald W. Rousseau
dc.contributor.committeeMember Sankar Nair
dc.contributor.committeeMember Satish Kumar
dc.contributor.department Chemical Engineering en_US
dc.date.accessioned 2012-02-17T19:20:27Z
dc.date.available 2012-02-17T19:20:27Z
dc.date.issued 2010-10-06 en_US
dc.description.abstract A new innovative polymer pyrolysis method was proposed for creation of attractive carbon molecular sieve (CMS) membranes. Oxygen exposure at ppm levels during pyrolysis was hypothesized and demonstrated to make slit-like CMS structures more selective and less permeable, which I contrary to ones expectation. Indeed prior to this work, any exposure to oxygen was expected to result in removal of carbon mass and increase in permeability. The results of this study indicated that the separation performance and CMS structure may be optimized for various gas separations by careful tuning of the oxygen level. This finding represents a breakthrough in the field of CMS membranes. Simple replacement of pyrolysis atmospheres from vacuum to inert can enable scale-up. The deviation in CMS membrane performance was significantly reduced once oxygen levels were carefully monitored and controlled. The method was shown to be effective and repeatable not only with dense films but also with asymmetric hollow fiber membranes. As a result, this work led the development of the "inert" pyrolysis method which has overcome the challenges faced with previously studied pyrolysis method to prepare attractive CMS membranes. The effect of oxygen exposure during inert pyrolysis was evaluated by a series of well-controlled experiments using homogeneous CMS dense films. Results indicated that the oxygen "doping" process on selective pores is likely governed by equilibrium limited reaction rather than (i) an external or (ii) internal transport or (iii) kinetically limited reaction. This significant finding was validated with two polyimide precursors: synthesized 6FDA/BPDA-DAM and commercial Matrimid®, which implies a possibility of the "inert" pyrolysis method application extending towards various precursors. The investigation was further extended to prepare CMS fibers. Despite the challenge of two different morphologies between homogeneous films and asymmetric hollow fibers, the "inert" pyrolysis method was successfully adapted and shown that separation performance can be tuned by changing oxygen level in inert pyrolysis atmosphere. Moreover, resulting CMS fibers were shown to be industrially viable. Under the operating condition of ~80 atm high pressure 50/50 CO2/CH4 mixed gas feed, the high separation performance of CMS fibers was shown to be maintained. In addition, elevated permeate pressures of ~20 atm did effect the theoretically predicted separation factor. While high humidity exposures (80%RH) resulted in reduced permeance, high selectivity was sustained in the fibers. Recommendations to overcome such negative effects as well as future investigations to help CMS membranes to be commercialized are provided. en_US
dc.description.degree PhD en_US
dc.identifier.uri http://hdl.handle.net/1853/42798
dc.publisher Georgia Institute of Technology en_US
dc.subject Membrane en_US
dc.subject Carbon molecular sieve en_US
dc.subject Gas separation en_US
dc.subject Carbon en_US
dc.subject.lcsh Molecular sieves en_US
dc.subject.lcsh Gas separation membranes en_US
dc.subject.lcsh Membranes (Technology) en_US
dc.subject.lcsh Separation (Technology) en_US
dc.subject.lcsh Adsorption en_US
dc.title Carbon molecular sieve membranes for natural gas separations en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Koros, William J.
local.contributor.corporatename School of Chemical and Biomolecular Engineering
local.contributor.corporatename College of Engineering
relation.isAdvisorOfPublication 0059291f-6b5a-4a6c-a661-eef665ac3a18
relation.isOrgUnitOfPublication 6cfa2dc6-c5bf-4f6b-99a2-57105d8f7a6f
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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