Mathematical model for supercritical fluid extraction of natural products and extraction curve evaluation

New model for supercritical fluid extraction (SFE) of natural products is presented. Like other models based on the concept of broken and intact cells, it is particularly suited to fit experimental data as it almost independently simulates two extraction periods, the first one governed by phase equilibrium and the second one governed by internal diffusion in particles. Its new feature is a detailed description of the first extraction period where different types of phase equilibrium and solvent flow patterns are taken into account. A simplified approximate form of the model is used to analyse its properties and to estimate its parameters. The number of model parameters is, in dependence on the complexity of the extraction process, 1-3 for phase equilibrium, 2-3 for mass transfer and 1 for flow pattern. The model is versatile, but, as a consequence, more data are necessary than a single extraction curve to determine its parameters in the first period. The evaluation of model parameters from extraction curves is shown on data sets from literature.