Thermophysical Characterization of Tetraethylammonium Chloride-Based Eutectic Solvents for Carbon Capture

New experimental data for the density, viscosity, and carbon dioxide (CO2) solubility in deep eutectic solvents (DESs) based on tetraethylammonium chloride ([TEA]Cl) combined with ethylene glycol (EG) and diethylene glycol (DEG) at molar ratios of 1:2, 1:3, and 1:4 are reported in this work. Density and viscosity were measured over a temperature range of 303.15 to 333.15 K, while CO2 absorption equilibrium isotherms were determined at 303.15 K for pressures up to 2.5 MPa. The density and viscosity of the investigated DESs decrease monotonically with increasing temperature and increase with hydrogen-bond donor content. DEG-based DESs exhibit systematically higher densities and viscosities than the corresponding EG-based systems. CO2 solubility increases with pressure across all DESs, indicating predominantly physical absorption. Higher CO2 solubilities are observed for DEG-based DESs and for DESs with higher hydrogen-bond donor fractions. The experimental data are modeled using the soft-Statistical Associating Fluid Theory (soft-SAFT) equation of state, and viscosity is rendered using Free-Volume Theory considering CO2 as a quadrupolar molecule. The model provides a consistent description of density, viscosity, and CO2 solubility, with low average deviations, and is also used to calculate Henry’s law constants and the enthalpy and entropy of CO2 dissolution.