Separation of Aromatics from a Cyclic-Aliphatic Hydrocarbon Using Ethylene Glycol and a Choline Chloride-Based Deep Eutectic Solvent
Mitra Khodabakhshitabar, Hamid Bakhshi, Mostafa Rahimnejad
Abstract
The separation of aromatic and aliphatic hydrocarbons is a challenging process in the petrochemical industry. In this case, liquid–liquid extraction (LLE) by organic solvents has been widely applied in the industry. However, most of the used traditional solvents are toxic and volatile. In the present work, two non-volatile and environmentally friendly solvents were utilized to separate toluene (as an aromatic) from cyclohexane (cyclic aliphatic) in an LLE process. Ternary phase diagrams of cyclohexane–toluene–solvent [ethylene glycol/deep eutectic solvent (DES)] were determined at 298.15 and 308.15 K and atmospheric pressure. The distribution coefficient and selectivity of applied solvents for toluene were determined and compared with those of previously used ionic liquids (ILs). The results show that the prepared choline chloride–glycerol DES in the current work is an efficient solvent for the extraction of toluene. The selectivity of applied DES was greater than unity and even higher than 9 at low concentrations of the solute. These values are higher than those of all previously used ILs. Two thermodynamic models of NRTL and UNIQUAC were used for the correlation of equilibrium data with a root-mean-square deviation value less than 0.028. Therefore, the mentioned models can be applied successfully for the design of the extraction process using the investigated solvents.