CO2 solubility in terpenoid-based hydrophobic deep eutectic solvents: An experimental and theoretical study

This research deals with the experimental measurement and molecular dynamics simulations of the CO2 capture in hydrophobic-based natural deep eutectic solvents (NADESs). First, Thymol and Menthol based NADESs were prepared in the appropriate mole ratios. The CO2 capture in the NADESs was evaluated using Henry's law constant at 298 K under the pressure up to 600 kPa. The best CO2 capture result was obtained for the eutectic mixture of Thymol:Camphor with the mole ratio of 4:6. The effects of the temperature, pressure, and the mole ratio of Thymol:Camphor on the capacity of the CO2 absorption were evaluated using the Response Surface Methodology/Central Composite Design (RSM/CCD) method. The obtained results using the RSM/CCD method presented the appropriate temperature and gas pressure for the optimized conditions of the CO2 capture. The molecular interactions in the DESs were analyzed using the investigation of the H NMR and FTIR spectroscopy and Thermogravimetric analysis. The molecular dynamic simulations, using the COMPASS force field and grand canonical Monte Carlo methods, were performed to examine the microscopic behavior of Thymol and Camphor with the CO2 molecule in three different molar ratios of the DES components. Radial distribution functions, mean square displacement analysis, and self-diffusion coefficients were also applied to interpret the solvent-solvent and solute-solvent interactions during the dissolving of the CO2 in the solvents.