Potential of pervaporation and gas separation membrane processes in solving challenging industrial separation problems

Pervaporation is the partial vaporization of a liquid mixture through a nonporous membrane and useful in breaking azeotropic and close boiling binary systems. Gas permeation is facilitated by the partial pressure gradient across a similar dense membrane and applied for air separation, purification of natural gas and biogas and even olefin-paraffin mixtures. These two processes are dealt with in terms of principle, mechanisms of separation, synthesis and characterization of appropriate membranes followed by case studies conducted in the laboratory which have lead to successful results. Some of the experimental data include dehydration of liquid propellants and separation of acid gases CO2 and H2S by gas separation. State-of-the art of both processes reveal that they have been commercialized in western countries for alcohol dehydration and natural gas sweetening, but could not make much headway in developing countries due to huge capital investment, operating cost and lack of awareness. The technical hurdles that need to be overcome for establishment of these separation techniques on an industrial scale are discussed. Future potential of both pervaporation and gas separation with respect to development of new membrane materials and process integration with fermentation, esterification, chemical absorption and solid phase adsorption is elucidated.