Production of biodiesel through optimized alkaline-catalyzed transesterification of rapeseed oil

Abstract

Present work reports an optimized protocol for the production of biodiesel through alkaline-catalyzed transesterification of rapeseed oil. The reaction variables used were methanol/oil molar ratio (3:1–21:1), catalyst concentration (0.25–1.50%), temperature (35–65 °C), mixing intensity (180–600 rpm) and catalyst type. The evaluation of the transesterification process was followed by gas chromatographic analysis of the rapeseed oil fatty acid methyl esters (biodiesel) at different reaction times. The biodiesel with best yield and quality was produced at methanol/oil molar ratio, 6:1; potassium hydroxide catalyst concentration, 1.0%; mixing intensity, 600 rpm and reaction temperature 65 °C. The yield of the biodiesel produced under optimal condition was 95–96%. It was noted that greater or lower the concentration of KOH or methanol than the optimal values, the reaction either did not fully occur or lead to soap formation. The quality of the biodiesel produced was evaluated by the determinations of important properties such as density, specific gravity, kinematic viscosity, higher heating value, acid value, flash point, pour point, cloud point, combustion point, cold filter plugging point, cetane index, ash content, sulphur content, water content, copper strip corrosion value, distillation temperature and fatty acid composition. The produced biodiesel was found to exhibit fuel properties within the limits prescribed by the latest American Standards for Testing Material (ASTM) and European EN standards.