Supercritical carbon dioxide extraction of acorn oil

Acorn fruit oil of Quercus rotundifolia L. (holm-oak) was extracted with compressed carbon dioxide in the temperature range of 35–60 °C and in the pressure range of 12–21 MPa. The influences of particle size, CO2 density, solvent flow rate, and extractor geometry were studied. Two different tubular extractors were used: extractor 1 of 0.2 L of capacity, internal diameter D = 45.7 mm, height/diameter ratio H/D = 1.5, and extractor 2 of 0.09 L of capacity, internal diameter D′ = 21.3 mm, and H′/D′ = 12.It was found that the yield and the initial extraction rate depend on the carbon dioxide density and superficial velocity, and on the ratio of bed height to D, at the same conditions of temperature, pressure, and particle size. In the beginning of extraction, CO2 density is the preponderant factor, but after some time of extraction, the fraction of oil directly exposed to the solvent, which is dependent on particle size, becomes the most important factor.The Sovová model was successfully applied to the description of the supercritical extraction curves of acorn oil.