Effect of Soap, Methanol, and Water on Glycerol Particle Size in Biodiesel Purification

Abstract

For use as a transportation fuel, biodiesel must meet certain quality standards (e.g., ASTM D6751 and EN 14214). Free dispersed particles of glycerol are among the important impurities in biodiesel that should be removed. The use of membrane separation technology to remove glycerol particles from fatty acid methyl ester (FAME) has been demonstrated to be an effective biodiesel purification method. The presence of large glycerol particles promotes its separation from FAME. The effect of water, methanol, soap, and glycerol on the size of suspended particles in FAME was studied using a three-level Box−Behnken experimental design technique. The statistical analysis revealed the significant effect of water and glycerol on increasing particle size while methanol and soap served to reduce the particle size. Experimental verification using a polyacrylonitrile (PAN) membrane at a temperature of 25 °C was completed. The addition of small amounts of water was found to improve the removal of glycerol from FAME, and a glycerol content as low as 0.013 mass %, well below the standard of 0.020 mass %, was achieved.