Dicyanamide-based ionic liquids in the liquid–liquid extraction of aromatics from alkanes: Experimental evaluation and computational predictions

Abstract

In this work, we have studied the potential use of the 1-allyl-3-methylimidazolium dicyanamide ([amim][DCA]) and the 1-benzyl-3-methylimidazolium dicyanamide ([bzmim][DCA]) ionic liquids (ILs) in the liquid–liquid extraction of aromatic hydrocarbons. To design an industrial process of extraction of aromatic hydrocarbons from alkanes, it is essential to measure the liquid–liquid and vapor–liquid equilibria between solutes and solvent, and to perform also a thermophysical characterization of the solvent. Because of this, we have studied the liquid–liquid extraction of toluene from n-heptane at 313.2K and the vapor–liquid separation of n-heptane from toluene in the presence of [amim][DCA] and [bzmim][DCA] at 323.2K, 343.2K, and 363.2K. Densities and viscosities as a function of temperature and the thermal stability of both ILs were also determined. The [amim][DCA] showed suitable extractive and physical properties to replace sulfolane and an adequate maximum operation temperature (MOT) to be employed at industrial scale. The ([bzmim][DCA]) showed good extractive properties but high viscosities. To complete the study, the Conductor-like Screening Model for Real Solvents (COSMO-RS) methodology was employed to predict the liquid–liquid and vapor–liquid equilibria between the hydrocarbons and ILs and the physical properties of ILs. A comparative evaluation between experimental results and COSMO-RS calculated values was performed.