Hydrolysis of soybean oil in a subcritical water flow reactor

Subcritical water has been recently demonstrated to be a viable medium for conducting hydrolysis reactions on a variety of organic compounds. In this study, the hydrolysis of triglycerides in soybean oil to their respective f ree fatty acids has been affected using a flow reactor. The flow reactor pe rmits hydrolysis to be accomplished without the need of a catalyst but requ ires higher temperatures than previously used in a static system to attain > 97% product conversion. Using a high pressure view cell as a diagnostic a id, it was found that the oil miscibility with water is crucial to attainin g a high conversion to the free fatty acids. Water to oil ratios of 2.5:1-5 :1 were found to optimal for high conversions as well as residence time bet ween 10-15 minutes in the open tubular reactor. Such rapid hydrolysis times contrast with multi-hour conversions utilized industrially to achieve a 96 -98% fatty acid yield. Although conversion of the all natural cis forms of the fatty acids to some trans form occurred, the isolated products were cle ar and free of degradation products, unlike previous results reported for t he reaction run in a closed vessel under static conditions at these elevate d temperatures (> 300 degrees C). Determination of the trans fatty acid con tent of aqueous hydrolyzed oils has not been previously reported, however t hey are of minor importance since the produced fatty acid mixtures are prim arily intended for industrial utilization and not for food consumption.