Alkylsulfate-based ionic liquids in the liquid–liquid extraction of aromatic hydrocarbons

The (liquid + liquid) equilibrium data (LLE) for the extraction of toluene from heptane with different ionic liquids (ILs) based on the alkylsulfate anion (R-SO4) was determined at T = 313.2 K and atmospheric pressure. The effect of more complex R-SO4 anions on capacity of extraction and selectivity in the liquid–liquid extraction of toluene from heptane was studied. The ternary systems were formed by {heptane + toluene + 1,3-dimethylimidazolium methylsulfate ([mmim][CH3SO4]), 1-ethyl-3-methylimidazolium hydrogensulfate ([emim][HSO4]), 1-ethyl-3-methylimidazolium methylsulfate ([emim][CH3SO4]), or 1-ethyl-3-methylimidazolium ethylsulfate ([emim][C2H5SO4])}. The degree of quality of the experimental LLE data was ascertained by applying the Othmer–Tobias correlation. The phase diagrams for the ternary systems were plotted, and the tie lines correlated with the NRTL model compare satisfactorily with the experimental data.

► Values of α2,1 for the four R-SO4 ionic liquids are higher than those of sulfolane.
► Values of D2 for all the ionic liquids are lower than those of sulfolane.
► Values of D2 for [emim][C2H5SO4] are the highest among the R-SO4 ionic liquids.