Supercritical fluids, technology

When a substance is brought above a particular critical temperature, Tc. and pressure, pc, and is unable to be condensed to a liquid by pressure alone, it exists in a condition called the supercritical fluid (SCF) state 

Baron Cagniard de la Tour [244] made the first reported observation of the occurrence of a supercritical phase in 1822. Tables 3.12 and 3.13 summarise some of the main useful features of SCFs. Several properties of SCFs make them ideal candidates as solvents for industrial extraction processes [245,246], 

The physical properties of a SCF are intermediate between those of a typical gas or liquid. For example, the diffusivity of a SCF is intermediate between a liquid and a gas and the viscosity is similar to a gas. The density of a SCF can be changed by varying the applied pressure on the fluid and can range between that exhibited by a gas to liquid-like values when the fluid is compressed 

After Lynch [89]. Reprinted from Journal of Chromatography Library, 56, T.P. Lynch, 269-303, Copyright (1995), with permission from Elsevier. 

After Harvala et al. [247]. Reprinted from Extraction 87, I. Chem. E Symposium Series, No. 103, T. Harvala et al, 233-243, Copyright (1987), with permission from Elsevier. 

In gas-assisted mechanical expression, liquid CO is introduced into the screw press under high pressure. This process takes advantage of the high solubility of dense CO in oil to enhance the extraction yield. Oilseed cell structure swells and eventually ruptures 

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General References Bruno and Ely, Supercritical Fluid Technologic ... 

The two fluids most often studied in supercritical fluid technology, carbon dioxide and water, are the two least expensive of all solvents. Carbon dioxide is nontoxic, nonflammable, and has a near-ambient critical temperature of 31.1°C. CO9 is an environmentally friendly substitute for organic solvents including chlorocarbons and chloroflu-orocarbons. Supercritical water (T = 374°C) is of interest as a substitute for organic solvents to minimize waste in extraction and reaction processes. Additionally, it is used for hydrothermal oxidation of hazardous organic wastes (also called supercritical water oxidation) and hydrothermal synthesis. 

Recent reviews of research in this area are Bruno and Ely, eds.. Supercritical Fluid Technology, CRC Press, 1991 Kiran and Bren-necke, eds., Supercritical Engineering Science, ACS, 1992. 

Carulite (Mn02/Cu0 on alumina) has shown exceptional performance for the complete rapid oxidation of phenol and other difficult substrates at temperatures just above T. The first full-scale SCWO plant has been commercialized by Huntsman, and it is expected that the technology will now become more mainstream as the value of different kinds of supercritical fluid technology becomes generally more widely appreciated and cost effective. 

Eggers, R., Supercritical fluid extraction (SFE) of oilseeds/lipids in natural products, in Supercritical Fluid Technology in Oil and Lipid Chemistry, King, J.W. and List, G.R., Eds., AOCS Press, Champaign, IL. 1996, 35. 

Supercritical fluid technology. . . 81 3.5.2 Solid-phase microextraction. 129... 

T.J. Bruno and J.F. Ely (eds), Supercritical Fluid Technology Reviews in Modern Theory and Applications, CRC Press, Boca Raton, FL (1991). 

Bruno TJ, Ely JF (1991) Supercritical fluid technology Reviews in Modem Theory and Applications. CRC Press, Boston... 

The authors would like to acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) and Alberta Agricultural Research Institute (AARI) for financial support of our research program on sub-/supercritical fluid technology applied to the extraction of phytochemicals from biomass. 

A number of techniques are based on supercritical fluid technology. Three are of particular pharmaceutical interest, namely the supercritical antisolvent (SAS) system, the rapid expansion of supercritical solution (RESS) method, and the gas antisolvent (GAS) technique [126]. 

Supercritical Fluid Technology for Drug Product Development, edited by Peter York, Uday B. Kompeiia, and Boris Y. Shekunov... 

York, P. and Hanna, M. (1996). Particle engineering by supercritical fluid technologies for powder inhalation drug delivery. Proc. Conf. Respiratory Drug Delivery V, Phoenix, AZ, 231-239. 

Kompella, U.B. and Koushik, K. (2001). Preparation of drug dehvery systems using supercritical fluid technology. Crit. Rev. Then Drug Carrier Syst., 18, 173-199. 

The most widespread application of supercritical fluid technology is for extraction purposes. 

J.W. King and G.R. List, Supercritical fluid technology in oil and lipid chemistry, AOCS Press, Champaign, Illinois, (1996). 

Supercritical fluid technology theoretical and applied approaches to analytical chemistiy / Frank V. Bright, editor, Mary Ellen P. McNally, editor. 

This volume spans these diverse areas and bridges the fields of modeling, spectroscopy, chromatography, and extraction. The contributors range from the academic, industrial, and governmental sectors. With this diversity, we have compiled an extensive volume that presents the current status of supercritical fluid technology. 

This volume serves as a link between researchers studying the more fundamental aspects of supercritical fluids and researchers involved in the application of supercritical fluid technology to solve difficult chemical problems. 

Over the past decade, much progress in supercritical fluid technology has occurred. For example, supercritical fluids have found widespread use in extractions (2-5), chromatography (6-9), chemical reaction processes (10,11), and oil recovery (12). Most recently, they have even been used as a solvent for carrying out enzyme-based reactions (14). Unfortunately, although supercritical fluids are used effectively in a myriad of areas, there is still a lack of a detailed understanding of fundamental processes that govern these peculiar solvents. 

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