High-Pressure Density of Bis(1-alkyl-3-methylimidazolium) Tetraisothiocyanatocobaltate Ionic Liquids: Experimental and PC-SAFT with Volume-Shift Modeling

Abstract

Tetraisothiocyanatocobaltate-based ionic liquids (ILs) have shown interesting thermophysical properties, mainly surprisingly low melting points and moderate viscosity. In addition, they have been tested to separate aromatics from aliphatics because of the high molar relation between cyano groups per molecule, with highlighted results. In this work, high-pressure density data (ρpT) were measured for bis(1-alkyl-3-methylimidazolium) tetraisothiocyanatocobaltate ILs ([CnC1im]2[Co(NCS)4]) (n = 1, 2) over wide ranges of temperature (283–363 K) and pressure (0.1–95 MPa). The new ρpT data and derivative properties, namely, the isothermal compressibility and isobaric expansivity, were successfully modeled with perturbed-chain statistical association fluid theory (PC-SAFT) and using the so-called volume shift, allowing us to propose a new molecular model and parameters for these solvents. The proposed model for tetraisothiocyanatocobaltate-based ILs is shown to be robust enough to model the phase equilibria of thi...