Continuous production of biodiesel via transesterification from vegetable oils in supercritical methanol

The continuous production of biodiesel (fatty acid methyl esters) by the transesterification reaction of coconut oil and palm kernel oil was studied in supercritical methanol without using any catalyst. Experiments were carried out in a tubular flow reactor, and reactions were studied at 270, 300, and 350 degrees C at a pressure of 10 and 19 MPa with various molar ratios of methanol-to-oils from 6 to 42. It was found that the best condition to produce methyl esters from coconut oil and palm kernel oil was at a reaction temperature of 350 degrees C, molar ratio of methanol-to-vegetable oil of 42, and space time 400 s. The % methyl ester conversions were 95 and 96 wt % for coconut oil and palm kernel oil, respectively. The regression models by the least-squares method were adequate to predict % methyl ester conversion with temperature, molar ratio of methanol-to-oil, and space time as the main effects. The produced methyl ester fuel properties met the specification of the ASTM biodiesel standards.