Comparison of biodiesel production from crude Jatropha oil and Krating oil by supercritical methanol transesterification

• Producing biodiesel from crude Krating and Jatropha oil via supercritical methanol.
• The highest FAME yield of 84.6% for Jatropha oil and 90.4% for Krating oil were obtained.
• The highest FAME yield of Jatropha and Krating oil were achieved at different condition.
• The presence of FFA has negligible effect in biodiesel via supercritical methanol.

This work compared the production of biodiesel from two different non-edible oils with relatively high acid values (Jatropha oil and Krating oil). Using non-catalytic supercritical methanol transesterification, high methyl ester yield (85–90%) can be obtained in a very short time (5–10 min). However, the dependence of fatty acid methyl ester yield on reaction conditions (i.e., temperature and pressure) and the optimum conditions were different by the source of oils and were correlated to the amount of free fatty acids (FFAs) and unsaturated fatty acid content in oils. Krating oil, which has higher FFAs and unsaturated fatty acid content, gave higher fatty acid methyl ester yield of 90.4% at 260 °C, 16 MPa, and 10 min whereas biodiesel from Jatropha oil gave fatty acid methyl ester yield of 84.6% at 320 °C, 15 MPa and 5 min using the same molar ratio of methanol to oil 40:1. The product quality from crude Krating oil met the biodiesel standard. Pre-processing steps such as degumming or oil purification are not necessary.