Exploring the potential of recovering 1-butanol from aqueous solutions by liquid demixing upon addition of carbohydrates or salts

Abstract

BACKGROUND: Fermentative production of 1-butanol yields dilute aqueous solutions. Recovery of the butanol from these solutions is most commonly performed by energy-intensive distillation. This work investigated the liquid-liquid (L-L) phase behavior of mixtures of butanol and water to explore the potential of using L-L phase separation as a recovery possibility for 1-butanol. The phase behavior is preferably influenced by compounds already present in the fermentation, such as carbohydrates and salts. RESULTS: The L-L phase equilibria of butanol and water were determined in the presence of glucose, fructose, sucrose, NaCl, LiCl and CaCl2. The aqueous and organic phase split is more pronounced in the presence of salts than in the presence of carbohydrates. Demixing is achieved with about 0.3 kg salt kg−1 aqueous phase containing 40 g of butanol. CONCLUSION: Operation of L-L based recovery using salts or carbohydrates requires extreme concentrations of those compounds. For feed material containing 40 g kg−1 butanol, the tested carbohydrates do not influence the phase equilibria sufficiently to allow butanol separation. Fermentative butanol concentrations up to 70 g kg−1 are required to create an effective L-L phase split. The remaining residual aqueous carbohydrate solution might be used as feed for a following fermentation. Copyright © 2011 Society of Chemical Industry