Thermodynamic modeling of liquid–liquid phase change solvents for CO₂ capture

A thermodynamic model based on Extended UNIQUAC framework has been developed in this work for the de-mixing liquid–liquid phase change solvents, DEEA (2-(diethylamino)ethanol) and MAPA (3-(methylamino)propylamine). Parameter estimation was performed for two ternary systems, H₂O-DEEA-CO₂ and H₂O-MAPA-CO₂, and a quaternary system, H₂O-DEEA-MAPA-CO₂ (phase change system), by using different types of experimental data (equilibrium and thermal) consisting of pure amine vapor pressure, vapor-liquid equilibrium, solid-liquid equilibrium, liquid–liquid equilibrium, excess enthalpy, and heat of absorption of CO₂ in aqueous amine solutions. 94 model parameters and 6 thermodynamic properties were fitted to approximately 1500 experimental data. The developed model accurately represents the equilibrium and thermal data for the studied systems with a single unique set of parameters. The model parameters are valid in the temperature range from −25 to 200 °C, CO₂ partial pressure from 0 to 945 kPa, and concentration of DEEA, MAPA, and CO₂ up to 131, 23, and 33 mol(kg H₂O)⁻¹, respectively. The model calculated speciation are also presented for the studied systems. The model developed in this work can be used for process simulation of CO₂ capture with aqueous blends of DEEA/MAPA.