Effect of Inclusion of 1-Butyl-3-Methylimidazolium Trifluoromethanesulfonate on CO2 and N2Permeabilities for PVDF and PVDF-HFP Membranes

Abstract

The CO₂ and N₂ permeabilities for polymer inclusion membranes, consisting of 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim][TfO]) in poly (vinylidenedifluoride) (PVDF) and poly (vinilidenedifluoride-co-hexafluoropropylene) (PVDF-HFP), at the temperatures from 298.2 K to 348.2 K, have been evaluated. The PVDF and PVDF-HFP membranes, containing 75 wt% of [bmim][TfO], had the CO₂ permeabilities of 585 and 976 barrers, respectively, and the CO₂ selectivities of 15 at 348.2 K. These values were higher than those of the supported ionic liquid membrane of [bmim][TfO] (428 barrers and 12). Furthermore, the Differential scanning calorimetry and Raman spectroscopy were performed to analyze the micro-structures of membranes. These analyses indicate that the polymer matrix was plasticized and the polymorphs changed from the non-polar a-phase to the polar b-phase by the addition of [bmim][TfO]. According to the solution-diffusion transport mechanism, it is concluded that the inclusion membranes with the sufficiently plasticized, i.e. phase-changed, PVDF and PVDF-HFP membranes absorbed the larger amount of gas species than the neat [bmim][TfO], and PVDF-HFP is more effective than PVDF for the enhancement in gas absorption.