Biodiesel from purified palm oil and palm fatty acid in supercritical methanol with sulfated zirconia catalyst

Abstract

This study investigated transesterification and esterification of purified palm oil and palm fatty acids in supercritical methanol with SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalyst. Firstly, the SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalysts were synthesized at different conditions, characterized, and the results were compared with the commercial SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalysts. Then, these catalysts were tested for the production of biodiesel by transesterification and esterification of purified palm oil and palm fatty acids. The most suitable catalyst was then selected for the study to determine the suitable operating conditions such as mass ratio of SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalysts to reactants (0-1 wt%), reaction temperature (200-300 °C), reaction time (0-15 minutes), and molar ratio of methanol to reactatant, (6:1-42:1) for purified palm oil and (3:1-12:1) for palm fatty acid, on fatty acid methyl ester (FAMEs) yield. Then the effect of catalyst recycling on the FAMEs yield were determined and presented. In this work, the suitable preparation condition of SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalyst was to immere 40 g of ZrO[subscript 2] in 18 ml of 0.1 mol/liter of H[subscript 2]SO[subscript 4] for 30 minutes at 70 °C, after which the catalysts were dried at 110 °C for 24 hours, and was calcined at 500 °C for 2 hours. The most suitable conditions for transesterification reaction of purified palm oil in supercritical methanol with SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalyst were the molar ratio of methanol to reactants of 24:1 and the catalyst to reactants mass ratio of 0.5% at 250 °C, and the reaction was 10 min. For palm fatty acid, the ratio of methanol to reactants of 6:1, the catalyst to reactants mass ratio of 0.5% at 250 °C, and the reaction time of 1 min were the most optimal conditions. About 80% FAMEs yield was achieved for both purified palm oil and palm fatty acid. However, the limitation of SO[subscript 4][superscript 2-]/ZrO[subscript 2] catalyst was its rapid deactivation, which nevertheless could be solved by re-impregnation and re-calcinations.