Conversion of oils to monoglycerides by glycerolysis in supercritical carbon dioxide media

Glycerolysis of soybean oil was conducted in a supercritical carbon dioxide (SC-CO2) atmosphere to produce monoglycerides (MG) in a stirred autoclave at 150-250 degrees C, over a pressure range of 20.7-62.1 MPa, at glycerol/oil molar ratios between 15-25, and water concentrations of 0-8% (wt% of glycerol). MG, di-, triglyceride, and free fatty acid (FFA) composition of the reaction mixture as a function of time was analyzed by supercritical fluid chromatography. Glycerolysis did not occur at 150 degrees C but proceeded to a limited extent at 200 degrees C within 4 h reaction time; however, it did proceed rapidly at 250 degrees C. At 250 degrees C, MG formation decreased significantly (P < 0.05) with pressure and increased with glycerol/oil ratio and water concentration. A maximum MC content of 49.2% was achieved at 250 degrees C, 20.7 MPa, a glycerol/oil ratio of 25 and 4% water after 4 h. These conditions also resulted in the formation of 14% FFA. Conversions of other oils (peanut, corn, canola, and cottonseed) were also attempted. Soybean and cottonseed oil yielded the highest and lowest conversion to MG, respectively. Conducting this industrially important reaction in SC-CO2 atmosphere offered numerous advantages, compared to conventional alkali-catalyzed glycerolysis, including elimination of the alkali catalyst, production of a lighter color and less odor, and ease of separation of the CO2 from the reaction products.