Continuous production of biodiesel using supercritical fluids: A comparative study between methanol and ethanol

Biodiesel was produced from vegetable oil (triglycerides) by transesterification with supercritical ethanol and carbon dioxide as cosolvent in the presence of solid acid catalyst. The objective of this work was to evaluate transesterification kinetics for biodiesel production from vegetable oil under supercritical conditions. Experimental investigation was carried out with vegetable oil and ethanol at molar ratio of 1:25, temperature between 150 and 200 °C, reaction time from 2 to 10 min and pressure around 200 bar in a continuous reactor. The biodiesel products were analyzed by gas chromatography. The effects of methanol to ethanol to temperature and reaction time towards biodiesel yield are discussed in detail. From this study, it was found than an optimum biodiesel yield of 80% can be attained at a relatively short reaction time around 6 min using supercritical condition with ethanol and carbon dioxide as cosolvent.