High-pressure carbon dioxide solubility in terpene based deep eutectic solvents

This work investigates carbon dioxide solubility in four type V natural deep eutectic solvents (NADES). The studied solvents have hydrophobic nature, and they were prepared by using carvone (CAR), cineole (CIN), thymol (THY), and menthol (MEN). Solubilities of carbon dioxide (CO2) have been determined via new apparatus that uses the isochoric saturation method. The apparatus has been validated against a widely used calibration fluid, which was selected as choline chloride (ChCl) and urea system, a.k.a. reline. The NADES have been tested at 25 °C and 35 °C isotherms and pressures up to 40 bars. Material characterization, including Fourier transform infrared (FTIR) and thermal gravimetric analysis (TGA), have been obtained and presented. The experimental heat of absorption of CO2 presented as a function of pressure, and the CO2 sorption kinetics presented based on the fractional amount of absorbed CO2 versus time. The results demonstrated that the solubility of CO2 in monoterpenoid-based hydrophobic NADES increased with increasing pressure and decreasing temperature. In addition to their hydrophobic nature, high CO2 sorption performance with rapid CO2 solubility rate make NADES good candidates for future carbon management applications.