Free solute content and solute-matrix interactions affect apparent solubility and apparent solute content in supercritical CO2 extractions. A hypothesis paper. http://dx.doi.org/10.1016/j.supflu.2011.10.006

Abstract

This manuscript stresses the need of experimental measurements and mathematical models of sorption isotherms/isobars to properly account for mass transfer in the SuperCritical (SC) Fluid Extraction (SCFE) processes. A reliable sorption isotherm/isobar model is a requirement, on one hand, for the determination of relevant inner mass transfer coefficients in SC CO2 extractions of vegetable substrates and other biological materials at the laboratory scale, and on the other hand, for a simulation tool successfully applicable to describe industrial SCFE process, which should be based both on a reliable mathematical descriptions of SC CO2 extraction processes. Having a reliable simulation model and model parameters would allow limiting expensive experimental pilot-scale work to validation purposes. Based on simulations of oil extraction from pre-pressed oilseeds using SC CO2 at 353 K and 90 MPa, this manuscript shows that the initial oil content in the pre-treated seed affects the apparent solubility of the oil, that the partition of the oil between the seed and CO2 affects oil yield, that it is difficult to discriminate oil partition from inner mass transfer effects, that the best-fit parameters from a mathematical model are adequate only when the model accounts for the true physical picture of the extraction process, and that failure of the mathematical model to account the true physical picture of the extraction process impedes reliable simulations, scale-up, and economical evaluation of industrial SCFE process. Being sorption phenomena of such paramount importance to build a reliable mathematical model for simulation of SCFE processes, this manuscript proposes a mathematical model that fits experimental sorption isotherm/isobars for oil from seeds.