CO2 desorption using ultrasound at low temperature from CO2-loaded amine solution under pressure conditions

Ultrasound can effectively desorb CO2 from dissolved CO2 gas [CO2 (aq)] in solution at low temperatures. In this study, three various classes (primary, secondary, and tertiary) of amine solutions were used as a CO2 absorbent for loading CO2 under 0.1 and 0.5 MPa. The effectiveness of ultrasound irradiation and stirring to desorb CO2 from CO2-loaded amine solution was evaluated at around 25 °C. The ultrasound had better desorption results than stirring for all three amines. Among the three classes of amine, tertiary amine triethanolamine with low pKa achieved the highest CO2 desorption ratio of 43.2% and 61.8% after CO2 loaded under 0.1 and 0.5 MPa by ultrasound. It was considered that amine with low pKa and strong sterically hindered structure can promote the balance of the rate-determining reaction of H+ transferred from amine cation to HCO3− and form CO2 (aq) after initial CO2 (aq) was desorbed by ultrasound.