Desorption kinetic model for supercritical fluid extraction of spearmint leaf oil

To characterize the dynamic behavior in supercritical CO₂ extraction of essential oil components (carvone and limonene) from spearmint leaves under pressures of 69.0 bar (near-critical), 84.5 bar (supercritical), and 103.4 bar (supercritical) and temperatures of 39 and 49°C, a simplified desorption kinetic model was developed. In the desorption model, a linear irreversible desorption kinetics was assumed, and the releasing rate of oil components from the leaf particle matrix was defined by a desorption rate constant as a model fitting parameter. Despite the simplicity of the desorption kinetic model, the experimental data and the predicted values by the desorption kinetic model were in good agreement. In the present study, the desorption rate constant mostly increased as the CO₂ flow rate and pressure were increased and as the temperature and leaf particle size were decreased.