Production of biodiesel from palm oil in supercritical methanol

Abstract

This study examines non-catalytic transesterification of palm oil in supercritical methanol. First, the reaction was carried out in a batch reactor at various temperatures between 250-300 ํC, the molar ratio of methanol to palm oil in range 6:1-45:1, and the reaction time between 10-230 min. The results demonstrated that the percent of methyl ester increased with increasing reaction temperature, molar ratio of methanol to palm oil, and reaction time. It was found that the best condition to produce methyl ester was at 300 ํC and molar ratio of methanol to palm oil of 45:1. At this condition the percentage of methyl ester produced was 85%, after 80 min reaction time. The first order kinetic was found to give suitable description of the reaction rate, and the activation energy of palm oil was estimated to be 86 kJ/mol. In addition, in this study, the effect of co-solvents (toluene, benzene and hexane) was examined and the results indicated that toluene and benzene could potentially be used as co-solvents in the reaction system, as they enhanced the production of biodiesel compared with the reaction without co-solvents. On the other hand, hexane was found to decrease the production yield for most of the conditions tested. Lastly, the continuous biodiesel production in a tubular flow reactor was evaluated at 300 ํC, with toluene and benzene used as co-solvents. In this experiment, the percent by volume of solvent to oil was 50% and the molar ratio of methanol to oil was 25:1. It was found that the increase in space time increased the yield of methyl ester. Based on the results of this study, it can be concluded that both batch and continuous systems have high potential for non-catalytic biodiesel transesterification in supercritical methanol