Extraction of aromatic hydrocarbons from pyrolysis gasoline using tetrathiocyanatocobaltate-based ionic liquids: Experimental study and simulation

The pyrolysis gasoline is one of the main sources of aromatic hydrocarbons as a result of their high content in these compounds. Organic solvents such as sulfolane are currently employed in the extraction of aromatic but the ionic liquids (ILs) have been recently proposed as potential replacement. In this work, we have studied the use of the bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate ([emim]2[Co(SCN)4]) and bis(1-butyl-3-methylimidazolium) tetrathiocyanatocobaltate ([bmim]2[Co(SCN)4]) ILs in the extraction of aromatic hydrocarbons from pyrolysis gasoline. The extractive properties of both tetrathiocyanatocobaltate-based ILs were compared to those of other promising ILs and sulfolane, showing the highest values. To perform the simulation of the whole process, we have experimentally studied the liquid-liquid extraction of aromatics from pyrolysis gasoline and the recovery of the extracted hydrocarbons from the ILs. In addition, a thermophysical characterization of the ionic solvents was performed measuring their densities, viscosities, thermal stabilities, maximum operation temperatures, and specific heats. Employing the experimental data, the extractor was simulated using the Kremser equation whereas the recovery section formed by flash distillation units was simulated using a new algorithm specifically design to the case of a high concentration of non-volatile compounds.