Crystallization fractionation of palm oil biodiesel as an alternative for improving its cold flow properties

Palm oil biodiesel (POB) has excellent properties as a fuel for engines. However, due to its highly saturated chemical composition, this biofuel presents a faulty performance at temperatures close to the environmental temperature of several Colombian cities. At 16 ºC, POB begins to form small crystals which grow and form agglomerates as the temperature continues decreasing, in such a way they can completely plug the fuel flow at temperatures between 12 ºC and 9 ºC. In this work, the fractionation technique of POB by crystallization induced by cooling was evaluated for improving its cold flow properties. The cooling or winterization temperature (Tw) and the stabilization time (ts) were the variables taken into account in the fractionation process. According to the values of the cloud point (CP) and pour point (PP) of the POB, the range for Tw tested was very limited (12 ºC-16 ºC). The process allowed the production of a liquid fraction, at Tw, with better cold flow properties than those of the original POB. For the extreme tested conditions (ts=24 hours and Tw=14 ºC), a liquid fraction having a CP of 6 ºC lower than the original POB was obtained. Such a change in the CP corresponded to an increase in the unsaturated methyl esters content of 4,7% and a reduction of the palmitic acid methyl esters content of 5,29%. The induced changes in the chemical composition of liquid fractions did not have significant effects on their fuel basic properties.