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.