398540 Effects of Branched and Cycloalkyl Functionality on CO2 Separation Performance of Poly(IL) Membranes

Monday, November 17, 2014
Galleria Exhibit Hall (Hilton Atlanta)
Spenser Hayward1, W. Jeffrey Horne1, Mary Andrews2, Matthew S. Shannon3, Kelsey Terrill4, Joshua Moon3 and Jason E. Bara3, (1)Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL, (2)Chemical Engineering, University of Alabama, Tuscaloosa, AL, (3)Chemical & Biological Engineering, University of Alabama, Tuscaloosa, AL, (4)Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL

The separation abilities of polymerizable ionic liquids (poly(ILs)) have been studied for the past several years, with a specific focus on their capabilities regarding CO2 removal. The structure of ILs allows for a wide degree of flexibility regarding the addition of functional groups, important because the molecular composition of IL monomers directly correlates to the monomer’s gas transport properties. Here, a variety of IL monomers were synthesized, with varying branched- and cycloakyl groups appended to the imidazolium ring. These monomers were used to form poly(IL) membranes. The permeabilities of each of these membranes to CO2, N2, and CH4 were then analyzed, and their selectivites for CO2 relative to other gases determined. Poly(ILs) with branched and cyclic functionalities exhibited ~20% larger CO2/N2 and CO2/CH4 selectivities than n-alkyl poly(ILs), while exhibiting a reduction in gas permeability of almost an order of magnitude. It is proposed that the greater selectivity of branched and cyclic functional groups is due to smaller fractional free volumes (FFV) than analogous n-alkyl chains. Computational analysis using COSMOTherm supports this.

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