Appliance of a high pressure semi-batch reactor: supercritical transesterification of soybean oil using methanol

Abstract This work presents the results of a supercritical transesterification process of soybean oil using methanol, performed in a laboratory high pressure semi-batch reactor. A full description of the equipment and a standard operating procedure are also provided. Since fossil fuels are not renewable, biofuels such biodiesel, have gained attention over the past decades. Biodiesel is the result of the transesterification of triacylglycerols in vegetable oils or animal fats and it works as an alternative fuel for compression-ignition engines. Methanol was chosen to perform the reaction, at molar ratios of 1:24 (oil: alcohol) and 0.1 (CO 2:methanol), temperature of 280 °C and pressure of 130 bar. In order to decrease the reaction time, CO2 in the supercritical state was used as cosolvent. The yield of biodiesel produced was equal to 95.19% in only ten minutes of reaction. A high yield of methyl esters (84.41%) was detected by gas chromatography-mass spectrometry. In general, 10 compounds were identified. The component in higher concentration was linoleate, followed by methyl hexadecanoate, oleic acid methyl ester and methyl stearate. The ester conversion rate means that the process with supercritical methanol can be successfully applied to produce biodiesel.