Gas–liquid separation processes based on physical solvents: opportunities for membranes

Abstract

Membrane contactors have received increased attention since the 1980s and are already used for different industrial applications. A very large number of studies have been reported, more specifically to achieve intensified gas–liquid mass transfer, almost exclusively in water or aqueous solutions. In contrast, the potentialities of membrane contactors for gas–liquid processes based on non-aqueous physical solvents are essentially unexplored. This study intends to discuss the difficulties associated with the specific physical solvent context and explore the potentialities of membrane contactors for both absorption and regeneration steps. Theoretical arguments show that dense membranes based on superpermeable and mechanically resistant polymers could offer promising performances, owing to their capacity to simultaneously prevent wetting effects, sustain a high transmembrane pressure and offer process intensification possibilities. Moreover, a significant improvement in terms of energy efficiency is theoretically achievable for the regeneration step. A preliminary proof of concept study, which supports these potentialities, is presented and the research needs for this new approach in order to possibly achieve applications at industrial scale are discussed.