Application of supported ionic liquid membranes (SILMs) for biobutanol pervaporation

• Pervaporation membranes were prepared within the system of double layers.
• The membranes were tested in the pervaporation plant for two different arrangements.
• Stable immobilization of ionic liquids in membranes was achieved.
• Double layers membranes with ILs were preferentially selective for butanol.

n-Butanol is a promising future biofuel. It can be produced in the so-called Acetone–Butanol–Ethanol (ABE) fermentation. The main drawback of this kind of fermentation is the toxicity of n-butanol towards the production strains. The concentration of butanol in the fermentation broth does not usually reach 2 wt.%. Biobutanol can be recovered continuously from the fermentation broth using pervaporation (PV), thus overcoming toxicity of n-butanol against microorganisms. To improve the separation efficiency of the membranes, supported ionic liquid membranes (SILMs) are used, in which ionic liquid (IL) is immobilized in the active layer of PV membranes. Two ionic liquids, namely trihexyl(tetradecyl)phosphonium tetracyanoborate (P6,6,6,14 tcb) and 1-hexyl-3-methylimidazolium tetracyanoborate (Im6,1 tcb) are immobilized by inclusion in a polyether block amide (PEBA) polymer matrix, which was covered by an additional silicone layer. Pervaporation experiments for these membranes were carried out at 37 °C using quaternary ABE mixtures with n-butanol concentrations up to 3 wt.% in the feed solution. It was found that permeate fluxes as well as selectivity of the SILMs can be influenced by immobilization of different ILs in the membranes.