Experimental investigation of novel ternary amine-based deep eutectic solvents for CO₂ capture

This study investigates the effect of using water as a low-viscosity component in ternary amine-based deep eutectic solvents (DESs) on the physicochemical properties, thermal stability, and CO₂ absorption capacity of the resulting DESs. It should be emphasized that water is a component of the ternary DES. The effect of water content in the DES, type of hydrogen bond acceptors (HBAs), hydrogen bond donors (HBDs), and HBA:HBD ratio on the above parameters was investigated. Moreover, the effect of temperature and pressure on the CO₂ absorption capacity of DESs was predicted using the predictive model COSMO-RS. This model was also used to predict the CO₂ solubility in the DESs and the results were compared with the experimental values. The results showed that the addition of small amounts of water, e.g., 5 and 10 wt% during preparation, can significantly decrease the viscosity of the resulting DESs, up to 25% at room temperature, while maintaining the high CO₂ absorption capacity and high thermal stability. The ternary DESs based on MEA exhibited a high CO₂ absorption capacity of 0.155–0.170 g CO₂ / g DES. The ternary DESs were found to be thermally stable with a decomposition temperature of 125C, which promotes the use of such solvents in post-combustion capture processes. Finally, COSMO-RS proved to be a suitable tool for qualitative prediction of CO₂ solubility in DESs and demonstration of trends related to the effects of temperature, pressure, molar ratio, water content, HBD and HBA on CO₂ solubility.