Optimization of alcoholic soybean oil extraction as a step towards developing in-situ transesterification for fatty acid isopropyl esters

Abstract As a step towards developing in-situ transesterification ( in-situ TE) for seed-to-biodiesel production, four solvents (methanol, ethanol, isopropanol and acetone; neat and in blends) were investigated for their potential in soybean oil extraction. Neat isopropanol compared favorably with the other solvents tested in terms of oil yield and properties of biodiesel product; thus, isopropanol was selected for process optimization of liquid-solid ratio (L-S ratio), shaking speed, extraction time and temperature. L-S ratio had the most significant effect on oil yield, and an increase in extraction temperature was able to reduce the solvent loading and improve the oil yield. Finally, in-situ TE was accomplished by applying the optimal conditions of isopropanol soybean oil extraction together with use of sodium catalyst. Applying optimal catalyst concentration and other process conditions, the yield of fatty acid isopropyl ester was 86.7% of the maximum theoretical yield. Moreover, the biodiesel had a low cloud point with −10 °C. This promising biodiesel yield, simple process and superior cold flow property suggests in-situ TE may be feasible as a small decentralized process for rural areas.