Phase separation of an acetone–butanol–ethanol (ABE)–water mixture in the permeate during pervaporation of a dilute ABE solution

•Phase separation in the permeate during the pervaporation of an ABE–water solution was studied.•Approximately 68 wt% ABE in the organic phase was obtained when phase separation occurred.•Ethanol and acetone hindered the phase separation in the permeate.•Phase separation more easily occurred at higher temperatures in the ABE–water solution.

When butanol and water are mixed at a proper ratio, phase separation can occur because of the immiscibility of butanol with water. A highly concentrated aqueous butanol solution in the organic phase can be obtained. Thus, in this study, the phase separation of the permeate was examined during pervaporation (PV) of an acetone–butanol–ethanol–water solution (ABE–water solution) to obtain a high permeate organic concentration. The effects of feed composition and operating temperatures on the phase separation of the permeate obtained during pervaporation of acetone–butanol–water and ethanol–butanol–water solutions were first evaluated with different membranes. Acetone and ethanol both hindered the phase separation of the permeate because of their miscibility with water and butanol. In the separation of the acetone–butanol–water solution, higher temperatures and lower acetone concentrations in the feed solution favored phase separation in the permeate, whereas for the ethanol–butanol–water solution, lower temperatures and lower ethanol concentrations in the feed solution led to relatively facile phase separation in the permeate. Pervaporation of a 1.5 wt% ABE–water solution with different membranes at different temperatures was also performed. When phase separation in the permeate occurred under proper conditions, the ABE concentration in the organic phase reached approximately 68 wt%.