Solid-liquid equilibrium of binary and ternary systems formed by ethyl laurate, ethyl palmitate and decylbenzene

Abstract

An experimental study of solid-liquid equilibrium of binary and ternary mixtures of ethyl laurate and ethyl palmitate, two ethyl esters frequently found in biodiesel, and decylbenzene, a representative aromatic compound present in conventional diesel, was carried out using differential scanning calorimetry (DSC). Such a study is of interest due to concerns about the economic and environmental sustainability of petroleum-based fuels, raising attention to alternative fuels, such as biodiesel. The binary mixture ethyl laurate + decylbenzene presents a eutectic point close to 255 K, whereas that of ethyl palmitate + decylbenzene is close to 258.8 K. The eutectic compositions, in decylbenzene mole fractions, are close to 0.80 and 0.97, respectively. Equilibrium data were modeled either considering that the liquid phase is an ideal mixture or using the UNIFAC-Dortmund and Flory-Huggins models for liquid-phase non-ideality. A simple eutectic behavior was observed for the binary system containing ethyl palmitate and decylbenzene, with an average deviation between calculated and experimental melting temperatures lower than 1.0 K. The binary mixture ethyl laurate + decylbenzene presents a more complex phase diagram, and the root mean-squared deviation is smaller than 2.3 K. Transitions of the binary system containing ethyl laurate and decylbenzene hardly influence the liquidus line of the ternary system. A good agreement was obtained between experimental and predicted data by using Flory-Huggins equation for liquid phase non-ideality and eutectic solid phase.