Transformation of Jatropha Seed to Biodiesel by In Situ Transesterification

Abstract

Abstract. The objective of this study was to investigate the in situ transesterification allowing to produce directly biodiesel from jatropha seed. Experiments were conducted using milled jatropha seed with moisture content of < 2% and mesh size of 20-35. The influences of amount of KOH catalyst, methanol to seed ratio, amount of n-hexane to methanol and seed ratio, stirring speed, temperature and reaction time were examined to define the best performance of biodiesel production yield and biodiesel quality. Generally, the methanol to seed ratio and amount of KOH affected biodiesel production yield and its quality. An increase of biodiesel yield and quality was observed as methanol to seed ratio and amount of KOH were increased. Highest biodiesel yield (76% with a FAME purity of 99.95%) and best biodiesel quality were obtained under methanol to seed ratio of 6:1 and amount of KOH of 0.075 mol/L in methanol. The acid value was < 0.3 mg of KOH/g, viscosity was < 3.5 cSt, and saponification value was > 210 mg of KOH/g. In addition, the amount of n-hexane to methanol and seed ratio affected biodiesel production yield. An increase of biodiesel yield was observed as amount of n-hexane to methanol and seed ratio was increased. The stirring speed, temperature and reaction time did not affected biodiesel yield. Highest biodiesel yield (89%) was obtained under amount of n-hexane to methanol and seed ratio of 3:3:1, stirring speed of 600 rpm, temperature of 40°C, and reaction time of 6 h. The effects of amount of n-hexane to methanol and seed ratio, stirring speed, temperature and reaction time on biodiesel quality were less important. In all experiments tested, the biodiesel quality was very good. The acid value was < 0.3 mg of KOH/g, viscosity was < 5.5 cSt, and saponification value was > 183 mg of KOH/g. The quality of biodiesel produced under optimal reaction condition was in accordance with the Indonesian Biodiesel Standard.