Physical Properties of Ternary Deep Eutectic Solvents for Efficient Removal of Phenol from Fuels

The efficient separation of phenol from fuels using environmentally friendly methods is of significant importance for the protection of the environment and the advancement of the petrochemical industry. This work designed and prepared seven novel ternary deep eutectic solvents (DESs) to efficiently remove phenol from toluene-simulated oil. Within the temperature range of 298.15–333.15 K, the physical properties of these DESs, including density, viscosity, surface tension, and refractive index, were systematically measured. Physical properties such as molecular volume, standard entropy, lattice energy, viscous flow activation energy, viscous flow activation Gibbs free energy, and surface entropy were also calculated. The effects of temperature and structure on the physical properties of DESs were comprehensively investigated, and the relationship between internal interactions and property changes was further explored. These DESs were then applied to the liquid–liquid extraction process of phenol. All DESs demonstrated excellent extraction performance, with extraction efficiencies exceeding 93%. Among them, the [TBAC–EG–LA] system exhibited the highest efficiency (95.82%). The study revealed that extraction efficiency negatively correlates with the viscosity, surface tension, and activation energy of viscous flow in DESs. This research provides crucial theoretical foundations and data support for designing efficient, low-cost green phenolic extractants.