(546b) Assessment of Cloud Point Depression and Solid Phase Behavior of Fatty Acid Ethyl Esters in the Presence of 3-Methylbutyl Dodecanoate

Biodiesel is a fuel obtained from renewable sources such as vegetable oils and animal fats through transesterification. Biodiesel performance is similar to that of conventional diesel and can be used directly in existing diesel engines and/or mixed in suitable proportions with conventional diesel. The solid-liquid phase behavior of biodiesel depends on the source of oils or fats and on the alcohol used in its production. Cloud and pour point of biodiesel can be reduced by blending it with conventional diesel, by using ethylic biodiesel or by adding crystallization inhibitors. However, common additives used for diesel have been shown to be ineffective in reducing biodiesel cloud point. Fatty esters obtained from branched-chain alcohols such as 3-methylbutyl dodecanoate (isoamyl laurate) have yielded satisfactory results both in decreasing the cloud point and increasing the induction time, which means that it can act both as thermodynamic and kinetic inhibitor. Despite this, the mechanism of action of this compound in the formation of the solid phase is not known, and detailed information on solid-liquid phase diagrams of systems containing isoamyl laurate and other fatty esters is scarce.

In this work, binary mixtures of ethyl palmitate (EP), ethyl myristate (EM) and ethyl oleate (EO) with 3-methylbutyl dodecanoate (3MBD) were analyzed by differential scanning calorimetry. Melting peak temperatures of the involved compounds are 297.6 K, 287.3 K, 254.2 and 258.03 K for EP, EM, EO and 3MBD, respectively. Results show the immiscibility of solid phase in all cases and reveal the existence of eutectic solid phases around 256 K, 255 K and 246 K, with eutectic compositions of ethyl ester close to 2.5%, 10 and 50% for EP, EM and EO, respectively. Equilibrium data were thermodynamically modeled using the UNIFAC-Dortmund model for liquid-phase non-ideality and considering experimentally obtained transition properties (melting temperatures and enthalpies). Best predictions were observed for the system containing ethyl palmitate. The systems containing ethyl oleate and ethyl laurate showed higher deviations that can be attributed to the polymorphism of these compounds in solid phase.