CO₂ absorption with aqueous tertiary amine solutions: Equilibrium solubility and thermodynamic modeling

In this work, the equilibrium CO₂ solubilities of five tertiary amines, namely Triethanolamine (TEA), N-methylethanolamine (MDEA), 2-(Dimethylamino)ethanol (DMEA), 3-dimethyl-amino-1-propanol (3DMA1P), and Diethylethanolamine (DEEA) were measured over the temperature range of 298.15–313.15 K, and at CO₂ partial pressures up to 60.8 kPa. The activity-structure relationship was studied on the molecular level to account for the differences in equilibrium CO₂ solubility. The M-KE model was applied to correlate the vapor-liquid-equilibrium data of the five tertiary amine-H₂O-CO₂ systems. Results show that the model is able to correlate experimental data very well and gives reasonable prediction results with average absolute deviation (AAD) of 2.5% for TEA, 3.3% for MDEA, 1.3% for DMEA, 1.0% for 3DMA1P and 0.8% for DEEA. In addition, the CO₂ absorption heat was calculated using the Clausius-Clapeyron equation. The potential for the five amines to be considered as alternative solvents for CO₂ capture was evaluated in terms of equilibrium CO₂ solubility, second order reaction rate constant and CO₂ absorption heat.