Interactions between molecular solutes and task-specific ionic liquid: Measurements of infinite dilution activity coefficients and modeling

Abstract

Infinite dilution activity coefficients of 35 molecular compounds in novel ionic liquid (IL) 1-(2-hydroxyethyl)-1-methylpyrrolidinium dimethylphosphate are presented in a wide range of temperature. Basic thermal characteristics and liquid density of the IL at ambient pressure are also reported. The measured activity coefficients are discussed in terms of molecular interactions between the solutes and the IL's cation and anion. An impact of strongly basic anion and the cation functionalization is elucidated. Application of the studied IL in aromatic-aliphatic separations and extractive desulfurization is evaluated on the basis infinite dilution selectivity and capacity. The experimental data are treated in terms of three distinct approaches: linear solvation-energy relationship (LSER), regular solution theory and conductor-like screening model for real solvents (COSMO-RS). In particular: temperature-dependent LSER correlation able to accurately reproduce gas-liquid partition coefficients derived from activity coefficients is presented, the solubility parameters of pure IL are derived on the basis of treatment of measured data with the Scatchard-Hildebrand equation and the predictive capacity of the COSMO-RS approach in calculating limiting activity coefficients for the considered systems is tested.