Experimental Measurements and Modeling Using tPC-PSAFT of the Phase Behavior of the Ternary Ionic Liquid System [bmim + ][NO 3 - ] + CO 2 + H 2 O Maaike C. Kroon 1,2 , Eirini K. Karakatsani 3 , Ioannis G. Economou 3,* , Maria D. Bermejo Roda 1,4 , Marta Montero 1,4 , Maria José Cocero Alonso 4 , Geert-Jan Witkamp 2 , and Cor J. Peters 1,* 1 Physical Chemistry and Molecular Thermodynamics Department of Chemical Technology, Faculty of Applied Sciences Delft University of Technology Julianalaan 136, 2628 BL Delft, The Netherlands 2 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 3 Molecular Thermodynamics and Modeling of Materials Laboratory Institute of Physical Chemistry National Center for Scientific Research “Demokritos” GR-15310 Aghia Paraskevi Attikis, Greece 4 Grupo de Procesos a Presión Departamento de Ingeniería Química y Tecnología del Medio Ambiente Universidad de Valladolid, Facultad de Ciencias, Prado de la Magdalena s/n, 47011 Valladolid, Spain *Corresponding authors: Economou@chem.demokritos.gr; C.J.Peters@tudelft.nl Abstract The phase behavior of the ternary ionic liquid system 1-butyl-3-methylimidazolium nitrate ([bmim + ][NO 3 - ]) + carbon dioxide (CO 2 ) + water (H 2 O) was studied experimentally using a synthetic method. Bubble-point pressures are measured for carbon dioxide concentrations ranging from 5 to 30 mole%, water concentrations ranging from 2 to 20 mole% and within a temperature range of 293 to 368 K. Thereafter, the phase behavior of this ternary system was modeled with the truncated Perturbed Chain Polar Statistical Association Fluid Theory (tPC-PSAFT) equation of state, which was recently developed for prediction of the phase behavior of binary ionic liquid systems. Here, this equation of state has been extended to ternary ionic liquid systems, so that the model is able to predict the phase behavior of the ternary system [bmim + ][NO 3 - ] + CO 2 + H 2 O. In general, good agreement with experimental data is obtained.