The Effect of Sulfate Electrolytes on the Liquid–Liquid Equilibrium of 2-MTHF/Water/5-HMF: Experimental Study and Thermodynamic Modeling

Abstract

We investigate the influence of sulfate salts and sulfuric acid on the equilibrium behavior of 2-methyltetrahydrofuran (2-MTHF)/H2O/5-hydroxymethylfurfural (5-HMF). Liquid–liquid equilibrium measurements are performed at atmospheric pressure and in a temperature range of T = (293–333) K. The compositions of the aqueous and organic phases, together with the dissociation state of the sulfate species, are determined with infrared spectroscopy and Indirect Hard Modeling. We show that the addition of the salts Na2SO4 and Li2SO4 results in salting out of 2-MTHF and 5-HMF from the aqueous phase. With increasing temperature, this effect gets less pronounced. In contrast, the addition of H2SO4 does not result in any salting-out behavior. The investigation of the dissociation states shows that H2SO4 dissociates to HSO4– while Na2SO4 and Li2SO4 dissociate completely to SO42–. Parameter regression is performed to model the liquid–liquid equilibrium with the electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) equation of state. For the analyzed salts, Na2SO4 and Li2SO4, the performed parameter regression accurately predicts the measurement results. Still, we observe slight deviations between measured values and modeling when predicting the liquid–liquid equilibrium and the liquid density in the presence of sulfuric acid.