Thermodynamics Research Center / ThermoML | Thermochimica Acta

ABSTRACT

In this study, the molar heat capacities, CP, of three choline chloride-based deep eutectic solvents (DESs), Reline, Ethaline and Glyceline, and their binary mixtures with water were determined. Using a heat flow differential scanning calorimeter, the heat capacities were measured at standard pressure from (303.2 to 353.2) K and over the complete range of composition. The measured CP were reported as functions of temperature and composition. Results showed that the molar heat capacity increased with increasing temperature and, for the binary systems, with increasing DES concentration. For the pure DESs, the temperature-dependence of the experimental data were successfully represented by a second-order empirical correlation using three fitting parameters with an overall average absolute deviation (AAD) of 0.05%. The excess molar heat capacities, CPE, of the binary mixtures were also calculated from the obtained CP data and were found generally negative over the whole composition range while exhibiting negative temperature dependence. The CPE values were fitted to a Redlich-Kister type equation to correlate them to the temperature and DES mole fraction. Consequently, the molar heat capacities of the binary mixtures were calculated. Upon comparison of the experimental and predicted results, the overall AAD was found to be 0.08%. It can be said that the applied models provided satisfactory representations of the experimental CP data as functions of both temperature and composition.