Exploring the Gas-Permeation Properties of Proton-Conducting Membranes Based on Protic Imidazolium Ionic Liquids: Application in Natural Gas Processing

Abstract

This experimental study explores the potential of supported ionic liquid membranes (SILMs) based on protic imidazolium ionic liquids (ILs) and randomly nanoporous polybenzimidazole (PBI) supports for CH4/N2 separation. In particular, three classes of SILMs have been prepared by the infiltration of porous PBI membranes with different protic moieties: 1-H-3-methylimidazolium bis (trifluoromethane sulfonyl)imide; 1-H-3-vinylimidazolium bis(trifluoromethane sulfonyl)imide followed by in situ ultraviolet (UV) polymerization to poly[1-(3H-imidazolium)ethylene] bis(trifluoromethanesulfonyl)imide. The polymerization process has been monitored by Fourier transform infrared (FTIR) spectroscopy and the concentration of the protic entities in the SILMs has been evaluated by thermogravimetric analysis (TGA). Single gas permeability values of N2 and CH4 at 313 K, 333 K and 363 K were obtained from a series of experiments conducted in a batch gas permeance system. The results obtained were assessed in terms of the preferential cavity formation and favorable solvation of methane in the apolar domains of the protic ionic network. The most attractive behavior exhibited poly[1-(3H-imidazolium)ethylene]bis(trifluoromethanesulfonyl)imide polymeric ionic liquid (PIL) cross-linked with 1% divinylbenzene supported membranes, showing stable performance when increasing the upstream pressure. The CH4/N2 permselectivity value of 2.1 with CH4 permeability of 156 Barrer at 363 K suggests that the transport mechanism of the as-prepared SILMs is solubility-dominated.

New PBI Membranes Doped with Methyl-Imidazolium Triflate Protic Ionic Liquid

“…The thermal stability of PBI-based membranes doped with [MeIm/TFSI], reported by Kalleme at al. [41], was found to be higher (tdec(10%)≈300°С) compared to the values obtained in this study. However, it should be noted that those membranes were prepared by infiltrating the microporous PBI support with ionic liquid.…”

Mixed Matrix Membranes

“…The combination of ionic liquids into a polymer matrix is an approach to enhance the mechanical stability of the separation process by avoiding working with a fluid phase [23,24]. This Special Issue presents an experimental study exploring the potential of supported ionic liquid membranes (SILMs) prepared by infiltration of protic imidazolium ionic liquids (ILs) into randomly nanoporous polybenzimidazole (PBI) membranes for CH 4 /N 2 separation [25]. The polymerization, monitored by Fourier transform infrared (FTIR) spectroscopy, and the concentration of the protic entities in the membranes evaluated by thermogravimetric analysis (TGA) were correlated to the gas permeability values of N 2 and CH 4 at 313 K, 333 K, and 363 K in terms of the preferential cavity formation and favorable solvation of methane in the apolar domains of the protic ionic network.…”

Study of Innovative GO/PBI Composites as Possible Proton Conducting Membranes for Electrochemical Devices

“…The electron-acceptor -NH-moieties of the benzimidazoles, i.e., bicyclic groups consisting of fused benzene and imidazole rings, are able to readily tether PA to form single-phase doped proton exchange membranes (PEMs) with improved proton conductivity [4,6]. Examples of applications are nanofiltration [12,13], gas separation [14,15], flow batteries [16,17], fuel cells [11,[18][19][20], and electrolyzers [21][22][23]. Flow batteries are promising devices for stationary energy storage characterized by environmental friendliness, design flexibility, extended lifecycle, and fast response times [24].…”