A comprehensive experimental and modeling study on CO2 solubilities in the deep eutectic solvent based on choline chloride and butane-1,2-diol

In this study, the performance of a novel DES, consisting of butane-1,2-diol as the hydrogen bond donor (HBD) and choline chloride as the hydrogen bond acceptor (HBA), was investigated thermodynamically for carbon dioxide absorption. The molar ratio of choline chloride to butane-1,2-diol was 1:4. Carbon dioxide solubilities in this DES were measured experimentally in a high-pressure equilibrium cell. The solubility measurements were carried out in a temperature range of 303.2 to 333.2 K, and pressures up to almost 3.4 MPa. The P-x isotherms showed an almost linear increase of solubility with increasing pressure. Based on the measured experimental data, the values of Henry's constants at very dilute concentrations were calculated, as well as the standard enthalpies, entropies, and Gibbs free energies of dissolution. By analyzing the calculated parameters, it was concluded that the dissolution process is exothermic, and that stronger interactions prevail in the mixture of carbon dioxide and the investigated DES, as compared to the interactions within the neat components. Finally, the Cubic Plus Association (CPA) and Soave-Redlich-Kwong (SRK) equations of state (EoSs) were used to model the experimental solubility data. Absolute average relative deviation percent (AARD%) values of 3.78% and 5.48% for the CPA and SRK EoSs, respectively, indicated good agreement with experimental values for both models. However, the CPA EoS achieved higher accuracy, and with much smaller values of binary interactions parameters, thus indicating the importance of considering association interactions for the accurate modeling of carbon dioxide solubilities in DESs.

Automated summary

In this study, the thermodynamic performance of a novel DES with butane-1,2-diol as the hydrogen bond donor and choline chloride as the hydrogen bond acceptor for carbon dioxide absorption was investigated. The experimental measurements of carbon dioxide solubility in the DES at various temperatures and pressures were conducted. The dissolution process was found to be exothermic, and the CPA EoS model achieved higher accuracy with smaller interaction parameters, indicating the importance of considering association interactions for accurate modeling of carbon dioxide solubilities in DESs.