Supercritical Fluid Extraction of Evening Primrose Oil - Kinetic and Mass Transfer Effects.

For processing utilization, supercritical fluid extraction requires a thorough understanding of the relevant phase equilibria, mass balance, and kinetic factors that impact on the successful recovery of extracts. In this study, we have determined the factors contributing to the kinetics and mass transfer of evening primrose oil (EPO) from its ground seed matrix, to supplement previously determined solubility data and chemical characteriza­tion of this oil moiety. The effect of extraction pressure, temperature, fluid density, and flow rate (over a threefold range) have been ascertained; the flow rate effect being correlated in terms of the extracted seed mass and similar data from the literature performed on a pilot and production plant scale. Using a dual mass transfer model, we have correlated the theory with extraction experiments conducted over a pressure range from 20-70 MPa, temperatures from 40°-60°C, and carbon dioxide flow rates in the interval from 9-27 g/ min. The agreement between the model calculations and experimental data is excellent allowing potential use of the data in process design