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This study was conducted to optimize the supercritical carbon dioxide (scCO2) extraction of oil from Gliricidia sepium seeds using response surface methodology. Initial experiments were carried out using scCO2 and scCO2 with co-solvent n-hexane to determine the effect of co-solvent addition in oil yield. In order to obtain the maximum yield, experiments were conducted using Response Surface Methodology - Face Centered Central Composite Design (RSM – FCCD) under the following conditions: pressure of 20, 30, and 40 MPa, temperature of 50, 60, and 70°C, and CO2 flow rate of 2, 2.5, and 3 mL/min. A second-order polynomial with extended cubic interaction model was significantly fitted (p < 0.05), and a high coefficient determination value (R2 = 0.98) was recorded. At a constant extraction time of 60 minutes, the best extraction yield (12.12%) was obtained at 60°C, 40 MPa, and 2.5 mL/min. The pressure, temperature, and CO2 flow rate were all found to have a significant effect on the oil yield. The oil was used in biodiesel production and its methyl ester composition was analyzed using Gas Chromatography-Flame Ionization Detector (GC-FID).
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