Aliphatic-aromatic separation using deep eutectic solvents as extracting agents

The separation of aliphatic and aromatic compounds is a great challenge for chemical engineers. There is no efficient separation process for mixtures with compositions lower than 20 wt % in aromatics. In this work, the feasibility of two different deep eutectic solvents (DESs) as novel extracting agents for the separation of the mixture {hexane + benzene} were tested. In order to select the proper solvent for this separation, a solubility test of a set of DESs was done at room temperature and atmospheric pressure. The selected deep eutectic solvents for this work were (i) tetrahexylammonium bromide:ethylene glycol with molar ratio = 1:2 (DES 1) and (ii) tetrahexylammonium bromide:glycerol with molar ratio = 1:2 (DES 2). The selected DESs were characterized by measurement of density and viscosity at atmospheric pressure and temperatures T = 293.2–343.2 K. Next, the liquid–liquid equilibria (LLE) of the ternary systems {hexane + benzene + DES 1} and {hexane + benzene + DES 2} were determined at T/K = 298.2 and T/K = 308.2 and atmospheric pressure. Besides, the solute distribution coefficient and selectivity values were calculated and compared to LLE data available in the literature for the studied ternary system with other solvents. Finally, the experimental data were successfully correlated using the nonrandom two-liquid (NRTL) model. The obtained results show that DESs are promising extracting agents for the industrial separation of low aromatic concentration naphtha streams