Vapor–liquid equilibrium in amino acid salt system: Experiments and modeling

Vapor–liquid equilibrium (VLE) measurements were carried out for both unloaded and CO2 loaded aqueous amino acid salt (AAS) solutions of the potassium salt of sarcosine (KSAR). Vapor–liquid equilibrium for unloaded solutions; 1.0–5.0 M KSAR was measured using a Swietoslawski ebulliometer for temperatures 40, 60, 80 and 100 °C and for total pressures 4.08–97.8 kPa while vapor–liquid equilibrium for CO2 loaded solutions of 3.5 M KSAR was measured using both low and high temperature VLE apparatuses for 40, 60, 80, 100 and 120 °C and for CO2 partial pressures ranging from 0.03 to 971 kPa. A thermodynamic model representing the AAS solvent system was developed using the extended UNIQUAC framework. The developed model accurately predicts the equilibrium speciation in loaded solutions from 13C NMR data and gives a very good representation of the solubility of CO2 in the amino acid salt solution as well as the total pressure of the unloaded system at all measured temperatures, loadings and pressures.