Comparison of glycerol ketals, glycerol acetates and branched alcohol-derived fatty esters as cold-flow improvers for palm biodiesel

Comparative results on the evaluation of cold-flow improvers for palm biodiesel, of the type glycerol ketals, glycerol acetates and branched alcohol-derived fatty esters, are presented. Glycerol ketals were obtained through the reaction of glycerol with acetone catalyzed by p-toluene sulfonic acid. Glycerol acetates were obtained through the reaction of glycerol with acetic acid catalyzed by p-toluene sulfonic acid. Branched alcohol-derived fatty esters were obtained through the esterification of palm-derived fatty acids with branched alcohols, catalyzed by sulfuric acid. These additives were mixed with palm biodiesel at levels of 1%, 3%, 5% and 10% and the effects on pour and cloud points were measured. Crystallization points of pure and additivated palm biodiesel were determined by differential scanning calorimetry (DSC). Effects of additives on the crystallization process were analyzed by measuring the size of crystals formed upon cooling. The best cold-flow improvers were 2-butyl esters of palm oil; upon addition of 5% of this additive the pour and cloud points were reduced about 6 °C. DSC analyses accurately showed that the additives decrease decrystallization points of biodiesel. Particle size analyses by dynamic light scattering showed that the additives act by decreasing crystal sizes; besides, this technique proved to be an easy and accurate way to determine the cold-flow behavior of biodiesel. Addition of 2-butyl esters of palm oil did not have any detrimental impact on the fuel properties of palm biodiesel.