Thermodynamic study of triacetin or ethyl levulinate and alcohol binary mixtures

Abstract

The subject of presented research is the study of liquid binary mixtures consisting of ester and alcohol combination; triacetin or ethyl levulinate, as one component, and ethanol or isobutanol, as second component. Thermodynamic and transport data were measured in the broad temperature range, T=(288.15/298.15–323.15/333.15) K, and at atmospheric pressure, p = 0.1 MPa. All corresponding excess and deviation properties were calculated including the excess molar volume, viscosity deviation, refractive index deviation, isentropic compressibility deviation and excess molar Gibbs energy of activation of viscous flow, and correlated with the basic Redlich-Kister equation. The analysis of possible chemical interactions and structural effects taking place in the mixtures was led in the terms of ester structure, complexity of ester molecule and chain length and branching of the alcohol molecule. The thermodynamic analyses showed change of the sign of the excess molar volume depending on the alcohol present in the mixture. FT-IR spectra were recorded for all four systems for the compositions where maximum excess molar volumes are obtained to support the conclusions derived from the mixtures’ nonideal behaviour. In addition, modelling of viscosity is performed with the two- and three-parameter correlative models, as well as excess molar volume correlation with the Peng-Robinson equation of state and three-parameter van der Waals mixing rule.