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

Biodiesel is a substitute fuel for petroleum-based diesel obtained from vegetables, formed by fatty acid methyl or ethyl esters produced by transesterification reaction between fats or oils and alcohols. An experimental study of solid–liquid equilibrium of ternary mixtures of ethyl esters commonly present in biodiesel (ethyl laurate, ethyl palmitate and ethyl stearate) 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 laurate and ethyl palmitate as well as ethyl laurate and ethyl stearate present eutectic points at ≥90% (m/m) of ethyl laurate, indicating solid phase immiscibility. The system ethyl palmitate and ethyl stearate forms solid solutions for all compositions (miscible system). The experimental results were modeled using the Flory–Huggins equation for liquid phase and, when applicable, solid phase non-ideality, with good agreement.