Supported ionic liquid membranes for the separation of methanol/dimethyl carbonate mixtures by pervaporation

Two supported ionic liquid membranes (SILM) based on 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C8MIM][NTf2]) and N-octyl-N-methylpyrrolidinium bis(triuoromethanesulfonyl) imide ([C(8)C(1)Pyrr][NTf2]) were prepared and studied for the pervaporation separation of binary mixtures of dimethyl carbonate (DMC)/methanol. Scanning electron microscope (SEM) analyses were carried out to evaluate the cross section morphology of the porous membranes before and after incorporating the ionic liquids. The pervaporation performance of SILMs was found to be highly concentration dependent. At low methanol concentration (0.2 M fraction), both SILMs tend to preferentially permeate DMC. In general, the SILM based on [C8MIM][NTf2] exhibited a better performance than the one with [C(8)C(1)Pyrr][NTf2]. Under optimal conditions, the SILM composed of [C8MIM][NTf2] enabled a transmembrane flux of 0.739 kg/m(2)h, a DMC/methanol selectivity of 67 and separation factor of 21 at 30 degrees C at 0.8 M fraction of DMC. However, at high concentration of methanol, the permeance of methanol increased due to coupling effects therefore decreasing the membrane selectivity to around 2.