Production Methyl Esters from Palm Fatty Acids in Supercritical Methanol

Abstract

This study investigated the biodiesel production via a noncatalytic esterification reaction in supercritical methanol. The palm oil fatty acids were chosen as the raw material because of its availability as a low cost byproduct of palm oil industry. The variables affecting the methyl ester (biodiesel) conversion were investigated, which included molar ratio of fatty acids and methanol (1:1 to 1:12), reaction temperature (250 to 300oC) and reaction time (from 10 to 80 min). The results from this study showed that esterification of palm oil fatty acids in supercritical methanol gave the high conversion of 94 % and was obtained at the fatty acids/methanol molar ratio of 1:6 and at 300oC after 30 min. Furthermore, water whose content in fatty acid between 0-30 %v/v was found to lower the yield of methyl ester by hydrolyzing methyl ester back to fatty acids, and the degree of hydrolysis increased as water content and reaction time increased. When compared the result of methyl ester yield obtained from methyl esterification of fatty acids with methyl transesterification of purified oil, it was found that the esterification of palm fatty acids requires lower operating conditions (molar ratio 1:6 versus 1:45 and time 30 min versus 50 min, respectively). When compared with conventional acid catalyzed process, supercritical methyl esterification of fatty acids required shorter reaction time (30 min versus 9 hr) and no neutralization process was needed. This suggests that palm fatty acids offer high potentials as more economical raw material for production of biodiesel.