Solid-liquid equilibrium of binary and ternary systems formed by ethyl laurate, ethyl palmitate and dodecylcylohexane: Experimental data and thermodynamic modeling

Abstract

The solid–liquid equilibrium diagrams of binary and ternary mixtures formed by dodecylcyclohexane and the fatty acid esters ethyl laurate and ethyl palmitate was determined herein. The liquidus and solidus lines were obtained through differential scanning calorimetry. The thermograms of pure compounds were resolved into the corresponding overlapping peak components by a fitting analysis, allowing a better estimation of phase-change properties of polymorphs. All binary systems show immiscibility in the solid phase, although those containing dodecylcyclohexane present small regions of partial miscibility. The system formed by ethyl palmitate and dodecylcyclohexane presents a peritectic transition, which was also observed in the ternary system. The thermodynamic modeling was conducted using different models for liquid-phase non-ideality and considering different polymorphs in solid phase. The modeling shows that a probable inversion of polymorphs relative stability occurs for the binary system formed by ethyl laurate and dodecylcyclohexane. The results from this work may contribute to enhancing the understanding and description of the complex behavior of biodiesel/diesel mixtures at low temperatures.