Pervaporation, as a downstream process for recovery of bio-fuels, derived from the fermentation of agricultural and waste biomass, is gaining wider relevance due to the advantages of lower costs and wider sustainability. Organophilic pervaporation of bio-butanol, an attractive fuel replacement/additive is especially favorable due to high selectivities and fluxes of butanol observed in literature .The various byproducts produced in the fermentation process, however, can convolute butanol selectivity and fluxes as complex functions of concentration and temperature. The present study aims at predicting membrane performance for refining bio-butanol by understanding the coupling of multiple components and interaction parameters between the various compositional and operational conditions the membrane is subjected to. Pervaporation was used to preferentially remove butanol from multicomponent Acetone-Butanol-Ethanol model fermentation mixtures (1.5-12wt % solvent). Single to multicomponent permeation studies were conducted on commercial organophilic membrane (PERVAP 4060, DeltaMem, Switzerland). Conventional one variable at a time approach was also used to study the effect of feed temperature and solvent concentrations for binary and ternary mixtures. Besides this, for higher-order mixture studies, orthogonal central composite design matrix was also used to identify and quantify the interaction between parameters. Solution Diffusion model and regression-based statistical models were used to fit the experimental data. Butanol separation was found to be concentration-dependent process with fluxes and selectivities not only being a function of operating conditions and butanol concentration in feed but also of acetone and ethanol concentrations. While the membrane itself was more selective to butanol (with permeance selectivity&gt;1) than ethanol and acetone (permeance selectivity&lt;1), low saturation pressure of acetone means that the driving forces and consequently separation performance towards acetone were preferentially enhanced than butanol. The interaction parameters involving acetone were also more significant than those involving ethanol.

Pervaporation for bio-refining of butanol from multicomponent fermentation broths: Effect of fermentation by-products on butanol recovery

ACS Spring 2022

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