(63b) Hydrophobic Natural Based Deep Eutectic Solvents for High Performance Carbon Dioxide Solubility

Natural deep eutectic solvents (NADES) were studied in this work on their carbon dioxide (CO2) capture performances. Monoterpenoids (cineole, carvone) were used as hydrogen bond acceptors (HBA), and they were mixed with other terpenes (menthol, thymol). The production of NADES systems was carried under specific conditions of mixing time, mixing speed, temperature, and molar ratio between the HBD and the HBA. These conditions were specified to reach the best point of eutectic between the HBD and the HBA. The optimized molar mixing ratios of the hydrogen bond acceptor and hydrogen bond donor have been identified by COSMO-RS calculations along with the sigma profiles for each eutectic system. Water content on these materials measured via Karl-Fisher coulometric titrator to confirm their hydrophobic behavior. Density, viscosity, conductivity, pH, surface tension and contact angle (on glass, stainless steel, copper) characterization at different isotherms have been carried out prior to experimental gas solubility tests. The carbon dioxide solubility experiments were performed in a high-pressure isochoric equilibrium autoclave. The carbon dioxide solubility experiments were conducted up to 40 bars at two isotherms (25°C and 35°C). The solubility data was benchmarked against the other state of the art solvents and emerging ionic liquid based solvents. The COSMO-RS solubility predictions were also used to compare the experimental findings against software predictions. The data has shown high solubility at low temperature isotherm around 40 bars. Carvone and Thymol based NADES has shown the highest solubility performance amongst the other studied NADES systems.

ADMETSTAR 2.0 toxicity calculations showed non-toxic behaviour on these NADES making them suitable agents for greener applications. Considering their low viscosity and high carbon dioxide solubility, these solvents and their other combinations with monoterpenoids can be considered for future applications in industry in large scales.