(529c) Development of a Robust Thermodynamic Model to Predict the Onset Crystallization Temperature of Fatty Acid Methyl Esters(FAMEs)

Current biodiesel mainly consists of fatty acid methyl esters and is viewed as an alternative to petroleum diesel for renewability and sustainability. Because the fatty acid profiles significantly varied for the sources, the compositions significantly affected the biodiesel properties, such as low-temperature performance. The cloud point of biodiesel indicates the phenomenon of solid-liquid phase change and can characterize the low-temperature performance. The statistical and phase-equilibrium models have been developed to predict the cloud point. However, these models for cloud point predictions were limited to known components in the mixtures. The binary and ternary mixtures of FAMEs were prepared from pure components, while multi-component mixtures were obtained from biodiesel with various feedstocks and fractionated with urea inclusion. Cloud points of all these mixtures were measured according to ASTM D 2500. With the application of phase equilibrium principles, a thermodynamic model was proposed, and the non-ideal behaviors were characterized by activity coefficients which were predicted by the UNIFAC model and Modified UNIFAC models. The developed thermodynamic model accurately predicts the cloud point according to compositions. The model extends the application scope to the low-temperature range. There had eutectic points in the phase diagrams when the mixtures consisted of either saturated FAMEs or unsaturated FAMEs. This study proved that saturated FAMEs regulate the cloud points, but unsaturated FAMEs affect them through group interactions. Moreover, the proposed model can predict unknown FAMEs mixture as it is built on the group contributions.