Shifting Desulfurization Equilibria in Ionic Liquid-Oil Mixtures

Ionic liquids (ILs) and deep eutectic solvents have been used for the extraction of molecules, particularly natural products. An often studied system is that for thiophene removal from oil. In the current study, ILs have been used for the removal of thiophene (Th), benzothiophene (BT), and dibenzothiophene by liquid-liquid extraction. The equilibrium can be shifted by polymerizing the thiophenic compounds both electrochemically and chemically. A 1:1 mixture of 1-butyl-3-methylimidazolium chloride (Bmim)Cl and FeCl3 was used to extract Th and BT from alkane layers using electropolymerization to shift the position of the equilibrium. While the process could be carried out, the kinetics of polymer formation were too slow to make this a viable process. The final part of the study used a 1:2 (Bmim)Cl/FeCl3 mixture to chemically remove sulfur-containing compounds from alkane layer. It was shown that the chemical polymerization reaction of Th is around 1500 times faster than electrochemical polymerization. Issues associated with the regeneration of the liquid are discussed.