Evaluation of CO2 solubility in potential aqueous amine-based solvents at low CO2 partial pressure

The cyclic capacity of various potential aqueous amine-based solvents was determined by performing CO2 absorption experiments at 30 °C and 10 kPa CO2 partial pressure and regeneration at 90 °C and atmospheric pressure. By comparing selected solvents the effect of molecule structure on the cyclic capacity and reactivity at low CO2 partial pressure was investigated in this work. 1,7-Diaminoheptane and 1,6-hexanediamine, N,N′-dimethyl showed a high cyclic loading of 0.81 and 0.85 moles CO2/moles amine respectively. Aqueous solutions of 1,6-hexanediamine, N,N′-dimethyl of 0.5 and 2.55 mole/L concentration were selected to study solubility of CO2 at different CO2 partial pressures ranging from 1 up to 40 kPa, 30 °C and at 1 atm. The solubilities of CO2 in aqueous 1,6-hexanediamine, N,N′-dimethyl at 30 °C were compared with CO2 solubility in aqueous solution of MEA of similar solvent molar concentrations. The solubility of CO2 in 2.55 mole/L 1,6-hexanediamine, N,N′-dimethyl was found to be almost twice that of 2.5 mole/L MEA at lower CO2 partial pressure.