Experimental and theoretical study on infinite dilution activity coefficients of various solutes in piperidinium ionic liquids

The aim of this work is to summarize our systematic studies on activity coefficients at infinite dilution (γ12∞) of various organic compounds and water in 1-n-alkyl-1-methylpiperidinium cation-based ionic liquids with bis[(trifluoromethyl)sulfonyl]imide anion, [CnC1Pip][NTf2] (n = 3–6). New sets of experimental data measured by gas-liquid chromatography are reported for 43 different solutes in [C5C1Pip][NTf2] and [C6C1Pip][NTf2] in temperature range T=(308.15T=(308.15 to358.15)358.15) K. Moreover, ambient pressure liquid densities of those ionic liquids are presented at different temperatures. The results are discussed in terms of an influence of structure of both solute and ionic liquid on γ12∞. Capabilities of the studied ionic liquids in liquid-liquid extraction of aromatics or sulphur compounds from aliphatic hydrocarbons are demonstrated in terms of infinite dilution selectivity and capacity. Finally, linear solvation energy relationship (LSER) theory and regular solution theory (RST) were used to analyze the obtained experimental data. In particular, correlative and predictive power of the most current version of the LSER is demonstrated and the Hildebrand’s solubility parameters are calculated as a function of temperature by using the RST.

► Limiting activity coefficients of 43 solutes in two piperidinium ionic liquids are presented. ► Potential applications of the studied ionic liquids in liquid–liquid extraction are discussed. ► Linear solvation energy relationship model is applied to represent the measured data. ► The regular solution theory is applied for estimating solubility parameters of ionic liquids.