In situ trans-esterification of oil-containing Jatropha curcas seeds to produce biodiesel fuel

The objective of this study was to investigate in situ trans-esterification allowing direct production biodiesel from jatropha seed. 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 yield and quality. Generally, methanol to seed ratio, amount of KOH and n-hexane to methanol and seed ratio affected biodiesel yield. An increase of biodiesel yield was observed as methanol to seed ratio, amount of KOH and n-hexane to methanol and seed ratio were increased. Stirring speed, temperature and reaction time did not affected biodiesel yield. Highest biodiesel yield (89%) was obtained under 6:1 methanol to seed ratio, 0.075 mole/L KOH in methanol, 3:3:1 n-hexane to methanol and seed ratio, 600 rpm stirring speed, 40 °C temperature and 6 h reaction time. The effect of process parameters on biodiesel quality was less important. In all experiments tested, the biodiesel quality was very good (acid value < 0.3 mg of KOH/g, viscosity < 5.5 cSt, saponification value > 183 mg of KOH/g). The quality of biodiesel produced under optimum reaction condition was in accordance with the Indonesian Biodiesel Standard. Keywords: biodiesel, in situ, jatropha seed, transesterificationAbstrakPenelitian ini bertujuan untuk memproduksi biodiesel secara langsung dari biji jarak pagar melalui proses transesterifikasi in situ. Parameter proses yang dipelajari adalah pengaruh konsentrasi katalis KOH, rasio metanol terhadap bahan, rasio n-heksan terhadap metanol dan bahan, kecepatan pengadukan, suhu dan waktu reaksi terhadap rendemen biodiesel dan kualitasnya. Rasio metanol terhadap bahan, konsentrasi KOH dan rasio n-heksan terhadap metanol dan bahan berpengaruh nyata terhadap rendemen biodiesel. Semakin tinggi rasio metanol terhadap bahan, konsentrasi KOH dan rasio n-heksan terhadap metanol dan bahan, rendemen biodiesel semakin meningkat. Kecepatan pengadukan, suhu dan waktu reaksi tidak berpengaruh nyata terhadap rendemen biodiesel. Rendemen biodiesel tertinggi (89%) diperoleh dari perlakuan rasio metanol terhadap bahan 6:1, 0.075 mol/L KOH dalam metanol, rasio n-heksan terhadap metanol dan bahan 3:3:1, kecepatan pengadukan 600 rpm, suhu 40 °C dan waktu reaksi 6 jam. Kualitas biodiesel yang dihasilkan dari proses transesterifikasi in situ biji jarak pagar pada seluruh perlakuan yang diuji sangat baik (bilangan asam < 0.3 mg KOH/g, viskositas < 5.5 cSt, bilangan penyabunan > 183 mg KOH/g), dan tidak dipengaruhi oleh parameter-parameter proses. Kualitas biodiesel yang dihasilkan dari kondisi proses optimum memenuhi Standar Biodiesel Indonesia.Kata kunci: biodiesel, in situ, biji jarak, transesterifikasi