Evaluation of COSMO-SAC method for the prediction of the alcohol-water partition coefficients of the compounds encountered in aqueous phase fructose dehydration

Liquid-liquid extraction of fructose, 5-hydroxymethylfurfural (HMF), and HMF rehydration products, levulinic acid (LA) and formic acid (FA), from aqueous solutions to C4 to C7 linear and branched alcohols was studied. The alcohol-water partition coefficients for these compounds were measured at 30 °C and 1 atm. The COSMO-SAC method was used to predict these partition coefficients and the water/alcohol and HMF/water/alcohol liquid-liquid equilibria. The predictions are in good agreement with experiments, and both show that the partition coefficients decrease with increasing the number of carbon atoms in the alcohols. Furthermore, with the same alcohol, the partition coefficient of HMF is higher than that of fructose and the HMF rehydration products. The agreement between the results of experiments and calculations indicates that the COSMO-SAC method is reasonable for the prediction of such thermodynamic data, and can be used to provide insights into the separations of these systems that is generally lacking in biomass processing. This is an important step towards screening organic solvents for liquid-liquid extraction that may preferentially extract HMF from an aqueous phase into an organic phase, thereby preventing HMF rehydration.