Highly Selective Separation of Carbon Dioxide from Nitrogen and Methane by Nitrile/Glycol-Difunctionalized Ionic Liquids in Supported Ionic Liquid Membranes (SILMs)

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• 作者：Sandra D. Hojniak ; Ian P. Silverwood ; Asim Laeeq Khan ; Ivo F. J. Vankelecom ; Wim Dehaen ; Sergei G. Kazarian ; Koen Binnemans
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：July 3, 2014
• 年：2014
• 卷：118
• 期：26
• 页码：7440-7449
• 全文大小：367K
• ISSN：1520-5207

文摘

Novel difunctionalized ionic liquids (ILs) containing a triethylene glycol monomethyl ether chain and a nitrile group on a pyrrolidinium or imidazolium cation have been synthesized and incorporated into supported ionic liquid membranes (SILMs). These ILs exhibit ca. 2.3 times higher CO<sub>2sub>/N<sub>2sub> and CO<sub>2sub>/CH<sub>4sub> gas separation selectivities than analogous ILs functionalized only with a glycol chain. Although the glycol moiety ensures room temperature liquidity of the pyrrolidinium and imidazolium ILs, the two classes of ILs benefit from the presence of a nitrile group in different ways. The difunctionalized pyrrolidinium ILs exhibit an increase in CO<sub>2sub> permeance, whereas the permeances of the contaminant gases rise negligibly, resulting in high gas separation selectivities. In the imidazolium ILs, the presence of a nitrile group does not always increase the CO<sub>2sub> permeance nor does it increase the CO<sub>2sub> solubility, as showed in situ by the ATR-FTIR spectroscopic method. High selectivity of these ILs is caused by the considerably reduced permeances of N<sub>2sub> and CH<sub>4sub>, most likely due to the ability of the 鈭扖N group to reject the nonpolar contaminant gases. Apart from the CO<sub>2sub> solubility, IL鈥揅O<sub>2sub> interactions and IL swelling were studied with the in situ ATR-FTIR spectroscopy. Different strengths of the IL鈥揅O<sub>2sub> interactions were found to be the major difference between the two classes of ILs. The difunctionalized ILs interacted stronger with CO<sub>2sub> than the glycol-functionalized ILs, as manifested in the smaller bandwidths of the bending mode band of CO<sub>2sub> for the latter.