(352ae) Properties of Multi-Phase Mixtures of Thermally Robust Peraryl Ionic Liquids and Aromatic Compounds

Authors: 
McGehee, J., University of South Alabama
West, K. N., University of South Alabama
Davis, J. H. Jr., University of South Alabama
Rabideau, B., Department of Chemical and Biomolecular Engineering
Bandlamudi, S. R. P., South Dakota School of Mines & Technology
Stoute, A., UNIV OF SOUTH ALABAMA, DEPT OF CHEMICAL & BIO
Ionic liquid (ILs) is a term that generally describes a salt formed of discrete cations and anions with a melting point near or below 100 °C. Recent years have seen a sharp increase in the study of ionic liquids due to their unique properties as tunable high activity solvents with negligible vapor pressures. Newly developed ILs based on tetraarylphosphonium cations paired with a bistriflimide anions have demonstrated extreme thermostability; withstanding temperatures in excess of 400 °C for extended periods of time (months) without significant degradation.

This thermostability allows for the use of ILs in high temperature applications such as chemical separations, high temperature reaction solvents, lubrication and thermal storage. The use of ILs in these applications would be valuable as the near lack of evaporation results in lower operating costs and less environmental contamination than traditional solvents. This work focuses on the determination of thermodynamic and physical properties of these thermostable ILs to enable the design of systems that utilize them.

To determine selectivity and molecular interactions, samples of

(4-phenoxyphenyl)triphenylphosphon-9-ium bis[(trifluoromethyl)sulfonyl]imide (POP) were allowed to reach equilibrium with substituted aromatic compounds in jacketed thermocells. Most solvents resulted in a binary phase equilibrium between an IL rich phase and a nearly pure aromatic phase. Gravimetric analysis was used to determine the selective solubility of POP as well as demonstrate the near temperature independent nature of the equilibrium system. The density of POP and the equilibrium mixtures were measured to investigate excess volume and strength of molecular interactions between the solvent and IL. Despite the relatively high melting point of POP (103.4 °C) the demonstrated meta-stable nature of liquid POP at temperatures far below its melting point (-80 °C) for long period of time allow for the direct measurement of its liquid phase behavior and heat capacity using DSC analysis.

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