Supercritical fluid extraction operational procedures

Regression correlation coefficient Regression coefficient of determination Rolling circle amplification Water solubility Sodium dodecyl sulfate Supercritical fluid extraction Standard operating procedure Solid-phase extraction Surface plasmon resonance Thymine... 

This chapter covers techniques for the extraction of semivolatile organics from solid matrices. The focus is on commonly used and commercially available techniques, which include Soxhlet extraction, automated Soxhlet extraction, ultrasonic extraction, supercritical fluid extraction (SFE), accelerated solvent extraction (ASE), and microwave-assisted extraction (MAE). The underlying principles, instrumentation, operational procedures, and selected applications of these techniques are described. In a given application, probably all the methods mentioned above will work, so it often boils down to identifying the most suitable one. Consequently, an effort is made to compare these methodologies. 

Supercritical fluid extraction has now found a lot of applications in different fields (polymers, aromas and essential oils, fats, natural products, soil decontamination...) and several production units are operated in agroalimentary (coffee, hop...) and pharmaceutical industries. In order to estimate the economical interest of these applications, technical and economical extrapolation methods have been developed. These methods are dependent of the nature of the extraction and are based on experimental results obtained on pilot plant units. We describe here a general extrapolation procedure, and a case study is presented to illustrate an economical estimation of a supercritical fluid extraction. 

For the case of a constant distribution coefficient, Treybal (1968) shows that the theoretical minimum solvent-to-feed ratio necessary to extract all of a component from a feed stream is equal to the inverse of the distribution coefficient. Recall, however, that the theoretical minimum value of the solvent-to-feed ratio requires an infinitely tall column. In actual practice a greater solvent-to-feed ratio, typically 1.3 to 1.5 times minimum, is employed. We present some elementary but informative graphical design procedures to illustrate the relationship between the distribution coefficient and the operation of the supercritical fluid extraction process for separating ethanol-water. 

The examples in this chapter highlight many facets of the development of SCF processes and applications that need to be addressed, understood, and solved before scaleup is considered. The same procedure is necessary for any kind of separation process. Supercritical fluid extraction has the potential to reduce energy costs but that does not necessarily mean it will be less expensive overall. Frequently, capital and other operating costs can more than offset decreased energy costs. Subsequent chapters discuss developments in the application of supercritical fluid solvents to the solution of technically and economically difficult separation problems in which the improved performance of the processed materials can support the processing cost. 

Extraction using a fluid in the supercritical state is a well-known procedure employed in the food industry. Analytical extractors operate on the same principle. They incorporate a very resistant tubular container in which is placed the sample (in solid or semi-solid form) with the fluid (CO2, N2O or CHCIF2 - Freon22) in the supercritical state. There are two modes of operation ... 

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