Experimental determination and thermodynamic modeling of solid-liquid equilibrium of binary systems containing representative compounds of biodiesel and fossil fuels: Ethyl esters and n-dodecane

Despite recent advances on biodiesel production, its behavior at low temperatures does not favor its use in aviation engines. A better understanding of the solid-liquid phase behavior of systems comprising fatty esters and components of conventional jet fuel is therefore necessary to investigate the possibility of this use of biodiesel. To extend the knowledge on these systems, this work evaluated the solid-liquid equilibrium of binary mixtures containing ethyl esters and a jet fuel constituent (n-dodecane) through differential scanning calorimetry. Experimental results confirmed the occurrence of polymorphism for all pure components in solid phase. A simple eutectic behavior was observed for the binary systems containing n-dodecane and either ethyl myristate or ethyl oleate. However, the pairs composed by the n-dodecane and ethyl stearate, ethyl palmitate or ethyl laurate presented different phase transitions and regions of partial miscibility. The thermodynamic modeling of this equilibrium was carried out using different liquid-phase activity coefficient models, viz. Flory-Huggins, UNIFAC-Dortmund and the ideal solution model. (AU)