Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

The paper presents new data on the activity coefficient at infinite dilution (gamma13(infinity)) for 29 various organic solutes: alkanes, alkenes, al-kynes, cycloalkanes, alcohols, ethers, ketones and aromatic hydrocarbons in two quaternary-ammonium based ionic liquids (quat-based ILs): didecyldimethylammonium perchlorate [DDA][ClO4] and didecyldimethylammonium tetrafluoroborate [DDA][BF4]. The activity coefficient at infinite dilution and physicochemical properties of two mentioned ionic liquids, were determined by inverse gas chromatography at four different temperatures: 308K, 323K, 338K and 353K. Additionally, on the basis of the specific retention volume (Vg0) the Flory - Huggins interaction parameters (chi(infinity)) were determined. In order to identify the fundamental interaction between solute and solvent inside the column, the partial molar excess enthalpies at infinite dilution (deltaH1E,(infinity)) were calculated on the basis of experimental gamma13(infinity) values. The selectivity (Sij(infinity)) and capacity (kj(infinity)) at infinite dilution for a few different separation problems: hexane/benzene, cyclohexane/benzene and hexane/tetrahydrofuran were calculated from the experimental gamma13(infinity) values to evaluate the possible use of the ionic liquids studied as a new class of solvents in liquid-liquid extraction and in other extraction or microextraction methods. The values of the above-mentioned parameters were compared and discussed taking into regard the chemical structures of both quaternary ammonium-based ionic liquids, including the same cation and their interactions with the organic solute.