Assessing the feasibility of deep eutectic solvents for CO₂ capture from molecular and process modeling

The soft-SAFT equation of state is employed for the screening of deep eutectic solvents (DES) for CO₂ capture based on key performance indicators, namely, CO₂ absorption capacity, and enthalpy of absorption. This work belongs to a long-term project on assessing the adequacy of advanced EoSs (soft-SAFT) as a tool for the evaluation and design of alternative solvents for CO₂ capture. The models for the pure DESs and their mixtures with CO₂ are validated with experimental data, and subsequently used in a fully predictive manner to calculate the thermophysical properties needed for evaluating solvent performance. Results demonstrate that under the same operating conditions, [TBA] [Cl]:LA (1:2) is the most promising DES in terms of amount of CO₂ absorbed and enthalpy of absorption. However, the comparison of these solvents to 30 wt.% aqueous MDEA solution shows that the promise of DESs is far from adequate in terms of CO₂ solubility, being 13 times lower than that obtained with aqueous MDEA. Nevertheless, DESs show a clear advantage in terms of lower enthalpy of absorption, being 3 times less than aqueous MDEA, along with the absence of water as a co-solvent. The collection of the acquired results confirms the reliability of the soft-SAFT EoS as an attractive and valuable screening tool for CO₂ capture and process modelling.