Effect of Free Fatty Acids on the Efficiency of the Supercritical Ethanolysis of Vegetable Oils from Different Origins

Abstract

This work studied the effect of the addition of free fatty acids (FFAs) at various proportions to different vegetable oils (soybean oil, rice bran oil, and high oleic sunflower oil) on the efficiency of their conversion to ethyl esters by a continuous supercritical ethanolysis. When the continuous reactor was operated at 300 °C and 20 MPa with soybean oil using an alcohol/oil molar ratio of 40:1, an ester content of 53% was obtained. Under identical conditions but processing soybean oil with 10% of FFAs, the ester content rose to 91%. A similar favorable effect of the addition of FFAs on the efficiency of the process was observed when processing rice bran oil and high oleic sunflower oil. Processing oils from different origins lead to different ester contents in the final product because of the occurrence of decomposition phenomena at different extents depending upon oil composition and stability. Results showed that the addition of FFAs is a useful tool for favoring alcoholysis against decomposition, with the consequence of a substantial increase in process efficiency.