Abstract: The potentialities of methylimidazolium-based ionic liquids (ILs) as solvents were evaluated
for some relevant separation problems—terpene fractionation and fuel processing—studying
selectivities, capacities, and solvent performance indices. The activity coefficients at infinite dilution
of the solute (1) in the IL (3), g¥ 13, of 52 organic solutes were measured by inverse gas chromatography
over a temperature range of 333.2–453.2 K. The selected ILs are 1-butyl-3-methylimidazolium
hexafluorophosphate, [C4mim][PF6], and the equimolar mixture of [C4mim][PF6] and
1-butyl-3-methylimidazolium chloride, [C4mim]Cl. Generally, low polar solutes follow
g¥ 1,[C4mim]Cl > g¥ 1,[C4mim][PF6]+[C4mim]Cl > g¥ 1,[C4mim][PF6] while the opposite behavior is observed for alcohols and water. For citrus essential oil deterpenation, the results suggest that cations with long
alkyl chains, such as [C12mim]+, promote capacity, while selectivity depends on the solute polarity.
Promising results were obtained for the separation of several model mixtures relevant to fuel
industries using the equimolar mixture of [C4mim][PF6] and [C4mim]Cl. This work demonstrates
the importance of tailoring the polarity of the solvents, suggesting the use of ILs with mixed anions
as alternative solvents for the removal of aliphatic hydrocarbons and contaminants from fuels.
This research was funded by the European Regional Development Fund (ERDF) through
the Regional Operational Program North 2020, within the scope of Project GreenHealth—Digital
strategies in biological assets to improve well-being and promote green health, Norte-01-0145-FEDER-
000042, to which A. Zambom is thankful for her grant. S. M. Vilas-Boas thanks FCT and the European
Social Fund (ESF) for his Ph.D. grant (SFRH/BD/138149/2018 and COVID/BD/152936/2022).
L.P.Silva acknowledges FCT for her Ph.D. grant (SFRH/BD/135976/2018).
