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Investigation of CO2-philic Oligomers for Carbon Dioxide/HydrogenMembrane Separations

Barillas, Mary Katharine (2011) Investigation of CO2-philic Oligomers for Carbon Dioxide/HydrogenMembrane Separations. Doctoral Dissertation, University of Pittsburgh.

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    Abstract

    The objective of this work was to design polymeric membranes that have very high CO2 permeability and high mixed gas selectivity toward CO2 rather than hydrogen. Therefore the membranes were based on "CO2-philic" polymers that exhibit thermodynamically favorable Lewis acid:Lewis base and hydrogen bonding interactions with CO2. CO2-philic polymers that are solid at ambient temperature include polyfluoroacrylate (PFA); polyvinyl acetate (PVAc); and amorphous polylactic acid (PLA). Literature CO2 permeability values for PVAc and PLA are disappointingly low. The cast PFA membranes from this study had low permeabilities (45 barrers at 25 oC) and very low CO2/H2 selectivity of 1.4. CO2-philic polymers that are liquid at ambient conditions include polyethylene glycol (PEG), polypropylene glycol (PPG), polybutylene glycol with a linear -((CH2)4O)- repeat unit (i.e. polytetramethylene ether glycol (PTMEG)), polybutylene glycol (PBG) with a branched repeat unit, perfluoropolyether (PFPE), poly(dimethyl siloxane) (PDMS), and polyacetoxy oxetane (PAO). A small compound, glycerol triacetate (GTA) was also considered because it is similar in chemical structure to a trimer of PVAc. These liquids were tested as supported liquid membranes (SLM) and also (with the exception of PAO and GTA) as rubbery, crosslinked materials. Mixed gas permeability was measured using equimolar mixtures of CO2 and H2 feed streams at one atmosphere total pressure in steady-state flux experiments over the 298 - 423 K temperature range. The most promising SLMs were those composed of a PEG, PTMEG, GTA, and PDMS. For example, at 37 oC the PEG-, PTMEG-, GTA- and PDMS-based SLMs exhibited CO2/H2 selectivity values of ~ 11, 9, 9, and 3.5, respectively, and CO2 permeability values of ~800, 900, 1900, and 2000 barrers, respectively. Crosslinked versions of the PEG, PTMEG and PDMS membranes at 37 oC exhibited selectivity values of ~ 5, 6 and 3.5, respectively, and CO2 permeability values of ~50, 300, and 3000 barrers, respectively.


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    Item Type: University of Pittsburgh ETD
    ETD Committee:
    ETD Committee TypeCommittee MemberEmail
    Committee ChairEnick, Robertrme@pitt.edu
    Committee MemberLuebke, Daviddavid.luebke@netl.doe.gov
    Committee MemberVelankar, Sachinvelankar@pitt.edu
    Committee MemberFederspiel, Williamfederspielwj@upmc.edu
    Title: Investigation of CO2-philic Oligomers for Carbon Dioxide/HydrogenMembrane Separations
    Status: Unpublished
    Abstract: The objective of this work was to design polymeric membranes that have very high CO2 permeability and high mixed gas selectivity toward CO2 rather than hydrogen. Therefore the membranes were based on "CO2-philic" polymers that exhibit thermodynamically favorable Lewis acid:Lewis base and hydrogen bonding interactions with CO2. CO2-philic polymers that are solid at ambient temperature include polyfluoroacrylate (PFA); polyvinyl acetate (PVAc); and amorphous polylactic acid (PLA). Literature CO2 permeability values for PVAc and PLA are disappointingly low. The cast PFA membranes from this study had low permeabilities (45 barrers at 25 oC) and very low CO2/H2 selectivity of 1.4. CO2-philic polymers that are liquid at ambient conditions include polyethylene glycol (PEG), polypropylene glycol (PPG), polybutylene glycol with a linear -((CH2)4O)- repeat unit (i.e. polytetramethylene ether glycol (PTMEG)), polybutylene glycol (PBG) with a branched repeat unit, perfluoropolyether (PFPE), poly(dimethyl siloxane) (PDMS), and polyacetoxy oxetane (PAO). A small compound, glycerol triacetate (GTA) was also considered because it is similar in chemical structure to a trimer of PVAc. These liquids were tested as supported liquid membranes (SLM) and also (with the exception of PAO and GTA) as rubbery, crosslinked materials. Mixed gas permeability was measured using equimolar mixtures of CO2 and H2 feed streams at one atmosphere total pressure in steady-state flux experiments over the 298 - 423 K temperature range. The most promising SLMs were those composed of a PEG, PTMEG, GTA, and PDMS. For example, at 37 oC the PEG-, PTMEG-, GTA- and PDMS-based SLMs exhibited CO2/H2 selectivity values of ~ 11, 9, 9, and 3.5, respectively, and CO2 permeability values of ~800, 900, 1900, and 2000 barrers, respectively. Crosslinked versions of the PEG, PTMEG and PDMS membranes at 37 oC exhibited selectivity values of ~ 5, 6 and 3.5, respectively, and CO2 permeability values of ~50, 300, and 3000 barrers, respectively.
    Date: 27 June 2011
    Date Type: Completion
    Defense Date: 04 April 2011
    Approval Date: 27 June 2011
    Submission Date: 21 March 2011
    Access Restriction: No restriction; The work is available for access worldwide immediately.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Doctoral Dissertation
    Refereed: Yes
    Degree: PhD - Doctor of Philosophy
    URN: etd-03212011-212637
    Uncontrolled Keywords: Carbon dioxide capture; Gas separation membranes; hydrogen; polyethers; liquid membrane; polymer membrane
    Schools and Programs: Swanson School of Engineering > Chemical Engineering
    Date Deposited: 10 Nov 2011 14:32
    Last Modified: 07 Mar 2012 14:42
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-03212011-212637/, etd-03212011-212637

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