Sodium Glyceroxide: An Efficient Homogeneous Alkaline Catalyst for Biodiesel Synthesis

Biodiesel is obtained from the alcoholysis of triglycerides and has been used as a renewable alternative to diesel. Though the methanolysis of triglycerides in the presence of MeONa catalyst has been widely used, searching for alternatives that may improve the competitiveness of the production chain is still a challenge. The aim of this work was to evaluate sodium glyceroxide as a catalyst in the methanolysis of soy oil. Sodium glyceroxide was obtained from glycerol and NaOH in ethanol, and characterized by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and, Fourier transform infrared (FTIR) spectroscopy. The transesterification reaction was optimized after two sets of experiments based on the Doehlert matrix experimental design. In the first one, the influence of the molar ratio of methanol/triglyceride, and the amount of catalyst (m/m with respect to the triglyceride) were studied. In the second set, the temperature, and the reaction time were studied. The best conditions were found as 12:1 molar ratio, 2% of catalyst, 50 ºC, and 60 min. The conditions were applied in the transesterification of canola and sunflower oils, and tallow. All the biodiesels were obtained with an ester content superior to 98%, free from methanol and triglycerides. Specific mass, viscosity, and pour point were determined and met the international specifications.

Keywords:
biofuel; biodiesel; sodium glyceroxide; transesterification; Doehlert matrix