Assessment of alcoholic extraction of Jatropha curcas L. oil for potential reactive extraction towards fatty esters

Abstract

This work dealt with the extraction of Jatropha oil using methanol and ethanol as solvents to evaluate a potential integration of extraction-transesterification to produce fatty esters. For comparison purposes, additional extractions were carried out with n-hexane as industrial benchmark solvent. The effects of type of solvent, particle size (0.44–3.57 mm), and seed-to-solvent ratio (1:4, 1:6, and 1:8 w/v) were evaluated with respect to oil yield, efficiency, saponification index (SI, mgKOH/g) and acid value (AV, mgKOH/g). As expected, highest oil yield (50.4% wt.) was obtained using n-hexane, but with a low selectivity to saponifiable materials (SI ∼ 166). When using alcohols, oil yield (8–31% wt.) and efficiency (17–70%) were lower and the quality of the oil was poor (SI 32–176; AV 4–5). Results indicated that, differently from previously claimed, integrated alcoholic extraction with alkaline transesterification would not be suitable for fatty esters production. By using experimental data and the Hildebrandt solubility parameters, it was possible to fit a continuous model suitable for further optimization and solvent selection in Jatropha oil extraction. The model was validated by predicting expected SI and oil yield using an untested solvent (i.e. petroleum ether), and difference between model predictions and experimental observations were less than 3%.