Synthesis and characterization of biodiesel obtained from castor oil transesterification

Abstract

The objectives of this work were to optimize the variables affecting transesterification process for biodiesel production from castor oil, non edible oil, by acid catalysis (sulphuric and phosphoric acid) and basic catalysis (potassium methoxide and potassium hydroxide); and to characterize the biodiesel for its use as fuel in compression ignition motors. The studied operation variables were methanol/oil molar ratio (3:1, 6:1, 9:1, 12:1), temperature (25, 35, 45, 55, 65 ºC), and catalyst amount (2, 3, 4 wt.% in acid catalysis, and 0.5, 1.0, 1.5 wt.% in basic catalysis). Evolution of each process was followed by gas chromatography, determining the content of methyl esters at different reaction times. Biodiesel was characterized by a set of parameter according to European Standard, EN 14214. The best conditions for transesterification process were 9:1 methanol/oil molar ratio, 65 ºC, and the use of potassium methoxide as catalyst with concentration 1.0 wt.%. In these conditions, obtained biodiesel presents satisfactory values of water content, iodine and saponification values, flash and combustion points, and temperature of 50% of distillate. However, values of density, kinematic viscosity, cetane index and cold filter plugging point, that are heavily dependent on oil, move away from those required by the European Standard.