Measurement and Separation of Sterol Glycosides in Biodiesel and FAME

Abstract

The major issue that hinder the widespread use of biodiesel is its poor cold weather stability and operability. This is attributed minor components identified as monoglycerides (MG), diglycerides (DG) and sterol glycosides (SG). There is currently no standard method to determine SG levels in biodiesel. A method to isolate and measure SG concentration in biodiesel and FAME was first developed. This was accomplished by decompatibilizing SG from the biodiesel matrix using n-dodecane and purifying the solids using a Folch liquid-liquid extraction. The extracted SG was analyzed by GC-FID; the tricaprin internal standard was detected at 21.5 min and SG from 26-26 min. Recovery using this method was 100% ± 2.5% when 3 commercial canola biodiesel samples were spiked with 38 ppm SG and extracted. This method was used to measure SG concentration of filtered FAME produced using 0.3wt%, 0.5wt% and 0.7wt% at a MeOH:Oil (mol/mol) ratio of 4:1, 5:1, 6:1, 7:1 and 9:1. The biodiesel produced was characterized according to ASTM D6584; MG, DG and TG decreased with increasing catalyst concentration and MeOH:Oil ratios. The SG solubility in reactive FAME was found to be lowest at high glycerol catalyst concentration. High levels of TG were found to solubilize SG in the reactive FAME. Finally, the solubility of SG in reactive FAME increased when high ratios of methanol were used.