Temperature gradients within the packed bed affect cumulative supercritical CO2 extraction plots for oilseeds

We studied the effect of temperature gradients within a packed bed on the SuperCritical (SC) CO2 extraction of oil from pelletized cranberry seeds. Temperature gradients were imposed on the extractor by using different temperatures for the SC-CO2 flow and the extractor vessel wall in heating and cooling experiments (60 and 40 °C, and viceversa) for oilseed pellets and glass beads at 48 MPa. A two-phase heat transfer model and a linear-driving-force mass transfer model described temperature profiles and oil extraction curves. Overall, temperatures in the packed bed were more affected by the vessel wall than the SC-CO2 inlet condition. Extraction curves for heating and cooling experiments were between the isothermal extraction curves for 40 and 60 °C, being affected by the vessel wall temperature in the solubility-controlled period of the extraction and approaching each other after 1-h of dynamic extraction. Both heat and mass transfer models allowed a satisfactory prediction of such a behavior and represent a step forward in the prediction of SC-CO2 oil extraction course.