Separation of the glycerol-biodiesel phases in an ethyl transesterification synthetic route using water

Abstract

Biodiesel is obtained by the transesterification of vegetable oil (or fat) and alcohol, with methanol being the most used alcohol. Methanol can be replaced by ethanol; however, this alcohol acts as a surfactant in the reaction mixture, promoting a stable dispersion of the glycerol in biodiesel, which hinders the separation of the glycerol-biodiesel phases. In this study, it was found that the addition of 1% v/v water relative to the total volume of the reaction mixture expedites the separation of the phases by interrupting the emulsifying action of ethanol with an immediate separation of glycerol from biodiesel. The characterization of the produced biodiesels was performed using hydrogen nuclear magnetic resonance (1H NMR) and gas chromatography (GC). 1H NMR indicated a 96.9% conversion of triglycerides to biodiesel. The fatty acid compositions of the synthesized ethyl and methyl biodiesels determined using GC are essentially the same.