Experimental and theoretical investigation of multistage extraction of 1,3-propanediol using the extraction system phosphate/1-butyl-3-methylimidazolium trifluoromethanesulfonate/water

The separation of 1,3-propanediol from fermentation broth is a challenging and energy-demanding step using conventional unit operations. One alternative process is the use of an aqueous two-phase system incorporating ionic liquids to use synergy effects of both technologies. Within this manuscript, the technical feasibility of the extraction of 1,3-propanediol using the aqueous two-phase system phosphate (salt)/1-butyl-3-methylimidazolium trifluoromethanesulfonate (ionic liquid)/water in a continuously operated process in pilot-scale is presented. The extraction was performed in a multistage mixer-settler unit and successfully modeled with an equilibrium-stage model and correlations to describe the liquid-liquid equilibrium of the salt/ionic liquid/water two-phase system. The developed and validated model was used for a further investigation of the influence of different process parameters in the determined operating window. Theses parameters include the number of stages, the phase ratio, the pH, and the mass fraction of the involved components. The results prove that the phosphate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate mass fraction, the phase ratio, and the number of stages have a considerable influence on the recovery of 1,3-propanediol, whereas the pH value has only a smaller impact. Those results can be used for optimization of the system as well as for targeting future research within this area. (c) 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:933-942, 2013