Solid–liquid equilibrium in ternary mixtures of ethyl oleate, ethyl laurate and ethyl palmitate

Biodiesel is a liquid mixture of fatty acid esters obtained through the reaction between fats or oils and alcohols. At low temperatures, the esters that constitute biodiesel tend to crystallize, which may be particularly critical for the biodiesel produced from ethanol, process little used or studied, although promising, since ethanol can also be obtained from biomass sources. In this work, an experimental study of solid–liquid equilibrium of ternary mixtures of ethyl oleate, ethyl laurate and ethyl palmitate was carried out using differential scanning calorimetry. Experimental results show that no eutectic composition is observed for ternary systems, although binary systems formed by ethyl oleate and ethyl laurate as well as ethyl laurate and ethyl palmitate present eutectic points at approximately 80% M ethyl oleate and 90% M ethyl laurate, respectively, indicating immiscibility in solid phase. The difference between the melting points in the case of the system ethyl oleate and ethyl palmitate causes ethyl oleate to act primarily as a solvent, being thus difficult to observe the eutectic point for this binary. Such results show that the solid–liquid phase equilibrium of these ternary mixtures cannot be seen as a simple extension of the solid–liquid equilibrium of the binary mixtures. The experimental results were also modeled considering that the liquid phase can be described by the Flory–Huggins activity model, with excellent agreement.