An RETM approach to model CO2 and H2S solubility in four protic ionic liquids using mSRK and CPA EoSs

Abstract

Reaction Equilibrium Thermodynamic Model (RETM) and the CPA EoS, were employed simultaneously to correlate CO2 and H2S solubility in four protic ionic liquids including, Methyldiethanolammonium Formate, Methyldiethanolammonium Acetate, Dimethylethanolammonium Formate, and Dimethylethanolammonium Acetate. RETM and CPA are responsible for complexation and phase equilibria calculations, respectively. The RETM defines a complex formation reaction of the AB2 type mechanism between two IL and a H2S/CO2 molecule into the liquid phase. Both of H2S and the ionic liquids were considered as association components following 4C and 2B schemes, respectively. Moreover, CO2 was assumed as a non-self-associating component with an electron acceptor site so that it can establish cross-association with the ILs.In the modeling procedure, after achieving the pure IL parameters, the binary systems were investigated. The essential physical properties of the ILs were estimated through the modified Lydersen-Joback-Reid method.To model binary systems, two scenarios were followed. In the first one, experimental liquid concentrations were used while the second approach calculated the liquid concentrations applying RETM so that, very good AAD% values for both CO2 and H2S solubilities. In addition to CPA, a modified version of SRK EoS was also implemented and its results were compared to those of CPA EoS. As anybody can observe from the results, RETM plays a vital role in reducing the deviations between model results and experimental values.