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Article

Thermodynamic Modeling of the Phase Behavior of Binary Systems of Ionic Liquids and Carbon Dioxide with the Group Contribution Equation of State

Bianca Breure,^† Susana B. Bottini,^‡ Geert-Jan Witkamp,^§ and Cor J. Peters*^†

Physical Chemistry and Molecular Thermodynamics, DelftChemTech, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands, PLAPIQUI, Universidad Nacional del Sur-CONICET, Camino La Carrindanga Km 7, Casilla 717, 8000 Baha Blanca, Argentina, and Laboratory for Process Equipment, Department of Process & Energy, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Leeghwaterstraat 44, 2628 CA Delft, The Netherlands

J. Phys. Chem. B, 2007, 111 (51), pp 14265–14270

DOI: 10.1021/jp0776098

Publication Date (Web): November 30, 2007

†

Faculty of Applied Sciences.

‡

Universidad Nacional Del Sur-CONICET.

Faculty of Mechanical, Maritime, and Materials Engineering.

Corresponding author.

Abstract

The group contribution equation of state (GC-EOS) was applied to predict the phase behavior of binary systems of ionic liquids of the homologous families 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrafluoroborate with CO₂. Pure group parameters for the new ionic liquid functional groups [-mim][PF₆] and [-mim][BF₄] and interaction parameters between these groups and the paraffin (CH₃, CH₂) and CO₂ groups were estimated. The GC-EOS extended with the new parameters was applied to predict high-pressure phase equilibria in binary mixtures of the ionic liquids [emim][PF₆], [bmim][PF₆], [hmim][PF₆], [bmim][BF₄], [hmim][BF₄], and [omim][BF₄] with CO₂. The agreement between experimental and predicted bubble point data for the ionic liquids was excellent for pressures up to 20 MPa, and even for pressures up to about 100 MPa, the agreement was good. The results show the capability of the GC-EOS to describe phase equilibria of systems consisting of ionic liquids.