Desulfurization of fuels by liquid–liquid extraction with 1-ethyl-3-methylimidazolium ionic liquids

• The ionic liquids [C2mim][OAc] and [C2mim][DEP] can be used as solvents in liquid–liquid extraction to desulfurize fuel oils.
• What happens not only with sulfur compounds but also with the other compounds of the fuel is decisive to suitably select the best solvent.
• These ionic liquids lead to higher selectivities and lower solubilities than the [C62,4mmpy][NTf2].
• The LLE data obtained were adequately correlated by means of the NRTL and UNIQUAC equations.

Although polysubstituted pyridinium-based ionic liquids are usually proposed for desulfurization of fuel-oils by liquid–liquid extraction, we have recently found that the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide shows better selectivities and it is a good alternative for this application. With the aim of avoiding the sulfur content in the anion, the desulfurization ability of two other 1-ethyl-3-methylimidazolium ionic liquids, acetate and diethylphosphate, has been studied in this work. For this purpose, liquid–liquid equilibrium data have been obtained for the ternary systems {ionic liquid + thiophene + toluene}, {ionic liquid + thiophene + n-hexane} and {ionic liquid + pyridine + n-hexane} at 298.15 K and atmospheric pressure. The obtained data have been satisfactorily correlated using the NRTL and UNIQUAC models. The solute distribution ratios and selectivities have been used to establish the influence of the anion of the ionic liquid in the extraction. Also, according to these parameters and in a, for us, closing work, a comparison among promising ionic liquids for this task has been established.

Ionic liquid + thiophene + n-hexane.Figure optionsDownload as PowerPoint slide