Geraniol and hydrophobic geraniol:thymol eutectic mixtures: Structure and thermophysical characterization

Abstract

The properties of essential oils as food preservatives are well-established. These components have also been used as neoteric solvents to prepare eutectic mixtures. Their high capacity to dissolve poorly water-soluble substances makes them particularly interesting in the biotechnology industry. To implement them, it is essential to determine the structural and chemical-physical properties, as well as develop models to predict the behaviour under any operational condition. Herein, pure geraniol and geraniol/thymol mixtures are studied. Nuclear magnetic resonance experiments and molecular dynamics are used to evaluate the fluid structure. In addition, seven thermophysical properties are measured and correlated. The experimental densities, surface tensions, and viscosities were lower than 952 kg m–3, 33 mN m–1, and 36 mPa s, respectively. These values were adequate for the industrial application of these mixtures. PC-SAFT equation of state well predicted the density with an average deviation of 0.13 %, and the isobaric molar heat capacity with a deviation of 6.9 %. Greater compaction was observed at higher thymol molar ratios and dispersive interactions were predominant. Depending on the composition, geraniol was both an acceptor and donor of hydrogen bonds; conversely, thymol acted as a donor. The article provides the necessary knowledge to be able to use these mixtures and design new ones, as ecological solvents in different applications including those in the agri-food sector.