Ethyl esters from the single-phase base-catalyzed ethanolysis of vegetable oils

The effects of alcohol/oil molar ratio, base concentration, and temperature on the single-phase base-catalyzed ethanolyses of sunflower and canola oils were determined. The use of tetrahydrofuran as co-solvent, as well as higher than usual alcohol/substrate molar ratios, prevented glycerol separation. This allowed each reaction to reach equilibrium rather than just steady-state conditions. High conversions of oil lowered the concentrations of MG and DG surfactants in the products, and thereby mitigated the formation of emulsions usually associated with ethanolysis reactions. An alcohol/oil molar ratio of 25:1, together with the necessary amount of cosolvent, gave optimal results. At this molar ratio, despite equilibrium being achieved, ethanolysis, unlike methanolysis, did not quite produce biodiesel-standard material, the MG content being approximately 1.5 mass%. For methanolysis and 1-butanolysis, the corresponding values were 0.6 and 2.0 mass%, respectively. The use of 1.4 mass% KOH (equivalent to 1.0 mass% NaOH) led to ethanolysis equilibrium within 6-7 min at 23degreesC rather than 15 min when only 1.0 mass% was used. At 60degreesC, equilibrium was reached within only 2 min. Soybean and canola oils behaved the same.