Supercritical fluid extraction modeling, applications

Kwak, T.Y., Mansoori G.A., Van der Waals mixing rules for cubic equations of state Applications for supercritical fluid extraction modelling. Chem. Eng. Set, 1986,47f5 , 1303-1309... 

The coupling of supercritical fluid extraction (SEE) with gas chromatography (SEE-GC) provides an excellent example of the application of multidimensional chromatography principles to a sample preparation method. In SEE, the analytical matrix is packed into an extraction vessel and a supercritical fluid, usually carbon dioxide, is passed through it. The analyte matrix may be viewed as the stationary phase, while the supercritical fluid can be viewed as the mobile phase. In order to obtain an effective extraction, the solubility of the analyte in the supercritical fluid mobile phase must be considered, along with its affinity to the matrix stationary phase. The effluent from the extraction is then collected and transferred to a gas chromatograph. In his comprehensive text, Taylor provides an excellent description of the principles and applications of SEE (44), while Pawliszyn presents a description of the supercritical fluid as the mobile phase in his development of a kinetic model for the extraction process (45). 

In this table, we provide solubility parameters for some liquid solvents that can be used as modifiers in supercritical fluid extraction and chromatography. The solubility parameters (in MPa1/2) were obtained from reference 3, and those in cal1/2cm 3/2 were obtained by application of Equation 4.1 for consistency. It should be noted that other tabulations exist in which these values are slightly different, since they were calculated from different measured data or models. Therefore, the reader is cautioned that these numbers are for trend analysis and separation design only. For other applications of cohesive parameter calculations, it may be more advisable to consult a specific compilation. This table should be used along with the table on modifier decomposition, since many of these liquids show chemical instability, especially in contact with active surfaces. 

The forerunner of all the recent applications of SCF technology reported in the United States is the SCF regeneration of activated carbon first described at an American Chemical Society meeting in 1978 (Modell, de Filippi, and Krukonis, 1978). The phenomena in operation during adsorption of organics from wastewater and the desorption of organics from the activated carbon using supercritical carbon dioxide are similar to those active in other supercritical fluid extraction processes. Therefore, we examine the technical details here. 

The Model 50 Supercritical Fluid Microextractor from the Suprex Co. (Pittsburgh, PA) was adapted for this design. A schematic of our multi-vessel extractor design can be found in Figures 1 and 2, for six and twelve multi-vessel systems, respectively. The following is a detailed description of the main components. The design, explained here for the extraction from six and twelve vessels is in principle applicable to any number of vessels, provided that other components of the system are scaled up. 

Serpil, T., Aeskenazi, O.N., Akman, U. and Horta9SU, 0. (1997) Application of serially-interconnected perfectly mixed tanks model to dense-gas extraction of plants, Proc. 4th Int. Symp. Supercritical Fluids, 299-302. 

Ethyl-lactate is a novel ecofriendly solvent with potential applications in supercritical fluid technology, as a co-solvent of earbon dioxide, in high pressiue chemical reactions, supercritical extraction processes and/or anti-solvent precipitation processes. In view of this, knowledge of the phase behavior of (ethyl lactate + CO2) binary is essential for the modeling and design of sueh proeesses. 

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