Thermophysical characterization of terpenoid based hydrophobic deep eutectic solvent and its Vapour-Liquid equilibrium studies with furfural

Abstract

The sustainable transition to cleaner production techniques over the last decade has projected deep eutectic solvents as alternative solvents to replace toxic volatile organic solvents especially in green extraction technologies. However, processes based on such newly developed solvents pose hindrances in industrial applicability due to lack of sufficient data for process design and scale up. Prospectively, a new hydrophobic deep eutectic solvent (HDES) that has been utilized for the selective extraction of biomass derived furfural from its aqueous solutions composed of thymol and 1-tetradecanol in 2:1 M ratio has been subjected to exhaustive thermo-physical characterization and phase equilibrium measurements in the present study. The various physico-chemical properties of the HDES such as density, viscosity, ionic conductivity as well as refractive index and acidity were measured as a function of temperature from 293.15 K to 333.15 K and suitably correlated. The thermal limit of operation for the HDES was analyzed through thermo-gravimetric analysis while its structural characterization was conducted by Fourier transform infrared spectroscopy. A modified Othmer type ebulliometer was used for the vapour pressure measurements of the HDES from 2.4 to 10.4 kPa and the experimental data was fit to the Antoine and Clark-Glew equations. Further, the isobaric vapour liquid equilibrium data at different sub-atmospheric pressures for the HDES and furfural system was generated and data regression using the non-random two liquid (NRTL) model was used to derive the optimized binary interaction parameters.