Equilibrium\nStudies of Biodiesel Ethyl Esters Prepared\nwith a Potassium Glyceroxide Catalyst

Biodiesel fuel is produced by the transesterification\nof triacylglycerides\nto alkyl esters using short chain alcohols, whereby ethanol represents\na safe, sustainable substitute for methanol. Due to the inherent solubility\nof the resulting fatty acid ethyl esters (FAEE) in residual ethanol\nsolvent, efficient phase separation of the postreaction mixture requires\nnear anhydrous initial conditions. A recyclable catalytic system of\n1:1 potassium glyceroxide:glycerol allowed for direct comparison of\nliquid–liquid phase equilibria between ethanol and methanol\ntransesterification reaction experiments with increasing water content.\nA maximum water tolerance of 1.06 mol water:1 mol catalyst was observed\nfor the ethanolysis reactions, representing a minimum of 4.6-fold\ngreater anhydrous stringency as compared to methanolysis reactions.\nThese results are supported by equilibrium calculations comparing\nmethoxide, ethoxide, and glyceroxide concentrations at 0%, 80%, and\n99% reaction completion. The catalyst system was applied to virgin\nsoybean and recycled canola oils, and mass balances, including distilled\nproduct yields, are presented. Additionally, life cycle assessment\nrevealed that biodiesel made from biobased ethanol and potassium glyceroxide\nresulted in approximately 20% reduction of greenhouse gases as compared\nto soybean methyl esters produced from sodium methoxide.