Synthesis of polyglycerol ester from glycerol for development in lubrication application

Abstract

The increase of bio-diesel utilization is playing an important role in an oversupply of glycerol. Therefore, there have been many attempts to create a demand for glycerol. One possible way is the conversion of glycerol to polyglycerol and then to react with fatty acid to obtain polyglycerol ester. Polyglycerol ester is considered to be a non-ionic surfactant, and it can be used in many applications (cosmetics, food and other industries). In this work, polyglycerol ester was prepared by a two-step reaction, the alkaline polymerization (etherification) of glycerol and the esterification of polyglycerol with fatty acid. For the etherification step, the reaction was performed under nitrogen atmosphere, and 2 % wt. of CaO was used as a catalyst with a reaction temperature of 240 °C. For 5 hours reaction time, di- and tri-glycerol yields of 36.2 % and 13.6 %, respectively were obtained. The unreacted glycerol was efficiently removed by using vacuum distillation at around 138 °C to 200 °C for 4 hours. Polyglycerol was then esterified with oleic acid in the range of 140 °C to 240 °C. The effects of various parameters were studied, such as reaction time and reaction temperatures in the esterification step. The changing of the polyglycerol ester from the viscous phase to the solid phase was initially observed with the lowest oleic acid-polyglycerol molar ratio of 1/10 at room temperature.