Properties Predictions of Ionic Liquid Mixtures Using Cubic Equations of State

Abstract

Interest in the properties of room-temperature ionic liquids (RTILs) is rapidly expanding due to their unique applications in thermodynamic applications, electrochemical applications, organic or inorganic synthesis and catalysis, and as a functional fluids. Their very unique properties like low vapor pressure, too poor conductors of electricity, non-ionizing, low combustibility, excellent thermal stability, and favorable solvating properties for a range of polar and non-polar compounds made them focused in industrial and academic community research. Hence, the knowledge of physical, chemical, and transport properties along with phase equilibrium behavior and solubility parameters calculation is very essential. Experimental data for various physical and chemical properties are available in literature. However, it is impossible to get experimental data for all possible ionic liquids. Moreover, systematic studies on models for prediction in absence of literature. So, various models on properties prediction obtained from literature and compared for accurate predictions. Special emphasize was be given to the use of Cubic equations of state (CEOS) as very few researchers have studied them for properties prediction of IL’s. Properties like boiling point, liquid density of ionic liquids, vapor pressure were found using thermodynamic models available in literature and comparative study was done to find consistent and accurate model(s) and alpha function(s) in association with CEOS. The correlation developed by Nasrifar and Moshfeghian in conjunction with the Predictive-Soave–Redlich–Kwong (PSRK) equation of state for prediction of saturated liquid density of ionic liquids has been generalized and results were compared with Linear Generalized Model recently proposed by Valderrama et. al., 2009 to check consistency and accuracy of generalized expression proposed in the present work for Nasrifar and Moshfeghian in conjunction with the PSRK equation of state. It was observed that CEOS can perform well for boiling point estimation and generalized model in conjunction with PSRK EOS was found to be accurate and appropriate for density prediction. The use of ILs as the potential solvents in the process of separation and extraction has got a wide range of active research. In recent years, room temperature ionic liquids are showing more and more promising perspectives in industrial waste gases separation, such as CO2, SO2, CO, H2 and so on. The accurate estimation of phase equilibria requires the knowledge of solubility parameters. In present work binary interaction parameters (BIPs) were optimized using different mixing rule and CEOS. The solubility of CO2 in two different ionic liquids were estimated using PE 2000, a powerful tool to correlate phase equilibria and variation of optimum BIPs with two different optimization methods were studied too. The results of PE 2000 were compared to a correlation, Recently developed by Reza Haghbakhsh et. al., 2013 for estimation of solubility of CO2 in ILs.