Understanding butanol recovery and coupling effects in pervaporation of Acetone-Butanol-Ethanol (ABE) solutions: A modelling and experimental study

The sustainable downstream recovery of bio-butanol from multicomponent fermentation broths through organophilic pervaporation is still challenged, in part, by a limited knowledge on the effect of by-products ethanol and acetone on final butanol recovery. This study therefore involves an experimental and theoretical inquisition on extraction of butanol and coupling effects involved between the various components. A commercial polydimethylsiloxane membrane was used for pervaporation of binary and ternary model solutions. Modified solution-diffusion based models were then customized to emulate temperature and concentration dependence of permeation. Membrane performance and coupling were found to be functions of the concentration of both organic components involved as well as temperature of the feed. The membrane was observed to be most intrinsically selective towards butanol in all systems. In ternary mixtures, the presence of second organic component positively enhanced coupling effects in favor of butanol recovery but lead to a decreased membrane plasticization by butanol itself. Ultimately permeance based coupling factors revealed that membrane permselectivity towards butanol was best benefited by coupling at lower butanol to ethanol/acetone concentration ratios in feed. In contrast, minimal coupling was experienced at equimolar conditions and multicomponent pervaporation in such cases could be satisfactorily modelled as binary mixture separation.