Study on Carbon Dioxide Capture Using Ternary Betaine-Based Deep Eutectic Solvents

The application of existing ternary betaine (Be)-based deep eutectic solvents (DESs) faces inevitable limitations due to the low regenerability and water absorption capability of the DESs. In this study, three ternary Be-based DESs with different molar ratios were prepared by adding the promoter diethanolamine (DEA) to the binary system of Be and ethylene glycol (EG). The effects of DEA, temperature, and flow rate on CO₂ absorption by the Be-based DESs were then investigated. At a molar ratio of 1:5:8 (Be:EG:DEA), the CO₂ absorption capacity reached 0.207 g CO₂/g DES at an absorption temperature of 30 °C and a gas flow rate of 50 mL/min. The addition of water with different contents triggered DES dissolution, forming a ternary Be-based DES + water system. The added water inhibited the absorption of CO₂ by the ternary Be-based DESs. Evaluation of the regenerability of the ternary Be-based DESs showed that their CO₂ absorption capacities remained above 0.176 g CO₂/g DES after five cycles of absorption-desorption.