Sulfonated Polyimide/Ionic Liquid Composite Membranes for CO2 Separation: Transport Properties in Relation to Their Nanostructures

• DOI: 10.1021/acs.macromol.8b01135
• Publication Date: 2018-09-07T17:53:44Z
• Authors: Akika Ito; Tomohiro Yasuda; Tetsuro Yoshioka; Akihiro Yoshida; Xiang Li; Kei Hashimoto; Kazukiyo Nagai; Mitsuhiro Shibayama; Masayoshi Watanabe
• Keywords: C4mim; Amide; Hexafluorophosphate

The transport properties of ionic liquid (IL)/sulfonated polyimide (SPI) composite membranes for CO2 separation were explored in relation to their nanostructures. 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C4mim][NTf2]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim]PF6), and 1-butyl-1-methylpyrrolidinium ([P14][NTf2]) selected as the ILs. These enable favorable superior mechanical properties. SPI is plasticized by IL, which induces a decrease elastic modulus; however, due formation bicontinuous nanostructures IL-rich SPI-rich phases, modulus >10 MPa retained even with incorporation 75 wt % IL. [C4mim][NTf2] [C4mim]PF6 exhibit stronger plasticization effects on than [P14][NTf2]. diffusion coefficients N2, measured time-lag method, abruptly increase increasing IL content [C4mim][NTf2]/SPI membranes, coincided change from an isolated continuous phase structure. On other hand, selective solubility exhibits no content. Consequently, permeation coefficient (PCO2) increases without decreasing factor (αCO2/N2), showing PCO2 = 431 barrer αCO2/N2 30 at °C.