Solvent supercritical fluids

Biocatalytic reduction has been performed in nonaqueous solvents to improve the efficiency of the reaction. This section explains the use of organic solvent, supercritical fluids, and ionic liquid. 

G. Vasopollo, L. Longo. L. Rescio and L.Ciurlia, Innovative supercritical C02 extraction of lycopene from tomato in the presence of vegetable oil as co-solvent../. Supercrit. Fluids 29 (2004) 87-96. 

The scope and limitations of biocatalysis in non-conventional media are described. First, different kinds of non-conventional reaction media, such as organic solvents, supercritical fluids, gaseous media and solvent-free systems, are treated. Second, enzyme preparations suitable for use in these media are described. In several cases the enzyme is present as a solid phase but there are methods to solubilise enzymes in non-conventional media, as well. Third, important reaction parameters for biocatalysis in non-conventional media are discussed. The water content is of large importance in all non-conventional systems. The effects of the reaction medinm on enzyme activity, stabihty and on reaction yield are described. Finally, a few applications are briefly presented. 

Organic solvents Supercritical fluids Solvent-free systems... 

A novel fluidized-bed coating process using the rapid expansion of supercritical solutions (RESS) is described for the encapsulation of fine particles [2,3]. This process exploits the capability of supercritical fluids to act as a selective solvent. Supercritical fluids are noteworthy in that their... 

The following table provides the solubility parameters, 8, for the most common fluids and modifiers used in supercritical fluid extraction and chromatography. The data presented in the first table are for carrier or solvent supercritical fluids at a reduced temperature, T of 1.02 and a reduced pressure, P of 2. These values were calculated with the equation of Lee and Kesler.1 2 The data presented in the second table are for liquid solvents that are potential modifiers.3... 

Energetic materials like TNT or other nitroaromatic compounds are readily soluble in liquid and supercritical carbon dioxide (SC-CO2). Extraction processes using SC-CO2 as an extracting solvent (supercritical fluid extraction SFE) permit the discharging of TNT and its breakdown products out of contaminated soils or other matrices [1],... 

In addition to common organic solvents, supercritical fluids (scf s) can be used for a great variety of extraction processes [158 165], Supercritical fluid extraction (SFE), mostly carried out with SC-CO2 as eluant, has many advantages compared to extractions with conventional solvents. The solvent strength of a supercritical fluid can easily be controlled by the pressure and temperature used for the extraction at a constant temperature, extraction at lower pressures will favour less polar analytes, while extraction at higher pressures will favour more polar and higher molar mass analytes. As supercritical fluids such as CO2 and N2O have low critical temperatures (tc = 31 °C and 36 °C, respectively), SFE can be performed at moderate temperatures to extract thermolabile compounds. Typical industrial applications using SC-CO2 include caffeine extraction from coffee beans [158] as well as fat and oil extraction from plant and animal tissues [165]. For some physical properties of supercritical solvents, see Section 3.2. 

The mixed-crystal system formed by indomethacin and saccharin (l,2-benzisothiazol-3(2H)-one-l,1-dioxide) has been used to evaluate the feasibility of using supercritical fluids as media for the design and preparation of new cocrystals [44]. In this work, the relative merits of supercritical fluid processes (i.e., cocrystallization with a supercritical solvent, supercritical fluid as anti-solvent, and the atomization and anti-solvent technique) were evaluated, as well as the influence of processing parameters on product formation and particle properties of the yields. It was reported that while the anti-solvent and atomization procedures yielded pure cocrystal products, only partial to no cocrystal formation took place when using the crystallization process. 

The use of supercritical fluids in separation processes has received considerable attention in the past several years and the fundamentals of supercritical fluid (SCF) extraction and potential applications have been described in a recent review article (p. It is generally known that supercritical conditions enhance the dissolution of solid particles. In comparison with liquid solvents, supercritical fluids have a high diffusivity, a low density and a low viscosity, thus allowing rapid extraction and phase separation. Little information is available in the literature however, on mass transfer coefficients between supercritical fluids and solids. 

Precipitation (salt or solvent supercritical Fluid) Few pLs to Liters Quick and scalable Solution composition not pharmaceutically relevant May lead to irreversible degradation No ... 

There are various possible approaches for multiphase operation of homogeneous catalysis, to improve their usability and recycle processes with organic/organic, organic/aqueous, or fluorous solvent pairs (solvent combinations), non-aqueous ionic solvents, supercritical fluids, and systems with soluble polymers. Figure 2.2 reports a general scheme of the possibilities for homogeneous catalysis. 

Keywoids. Environmentally benign synthesis, Catalysis, Green solvents. Supercritical fluids. Carbon dioxide. 

Supercritical fluid extraction (SFE) is a separation technique that uses sc-fluids as separating solvents. Supercritical fluids can replace other solvents in many purification procedures, even in countercurrent extraction. In synthetic chemistry, SFE can be an alternative to conventional methods for purification/isolation of complex products, for example pharmaceuticals, nutraceuticals and vitamins [12, 18j. Since SFE is still quite a young discipline, physical properties and basic parameters for many interesting compounds and mixtures are not yet known (in contrast to classical methods like distillations). Therefore, it must be pointed out that for all applications of sc-fluids the phase equilibria have to be determined properly. Unfortunately, for many technical or industrial applications of procedures based on supercritical fluids, the basic parameters are often not yet known. For industrial implementation, scale-up, miniplant, or pilot plant activities, it is absolutely necessary to have information about phase behaviour, solubility, energy balances and... 

Tlie usefnlness of enzymes is being enhanced by deploying them in organic solvents ratlier tlian aqneons media. In such solvent or solvent-water mixtiu es enzymes can catalyze reactions impossible in water, display greater stability and show behavior such as molecular memory. Enzymatic selectivity, and substrate-, stereo-, regio- and chemo-selectivity are affected and occasionally modified by the solvent. Enzyme reactions of industrial applicability have been demonstrated in organic solvents, supercritical fluids and the gaseous phase.[4 l... 

One of fee key areas within fee realm of green chemistry is fee identification of environmentally benign, alternative solvents ftiat can replace fee conventional, toxic, volatile organic solvents. Supercritical fluids (SCF) offer great... 

Environmentally benign solvents (supercritical fluids, ionic liquids, low melting polymers (especially PEG), perfluorinated solvents and water) in organic synthesis, particularly, that of heterocycles 05COC195. 

A product may be removed from its producing cell by five main possible techniques. Evaporation occurs via stripping, (vacuum) distillation or by membrane-supported techniques such as pervaporation and transmembrane distillation. Extraction into another phase includes the use of water-immiscible organic solvents, supercritical fluids, or an aqueous two-phase system. In addition, the... 

Overview. Polychlorinated Biphenyls. Polycyclic Aromatic Hydrocarbons Determination. Polymers Natural Rubber Synthetic Polyurethanes. Quality Assurance Quality Control Instrument Calibration Interlaboratory Studies Reference Materials Production of Reference Materials Method Validation Accreditation Clinical Applications Water Applications. Sample Handling Comminution of Samples Sample Preservation Automated Sample Preparation Robotics. Sampling Theory Practice. Solvents. Supercritical Fluid Chromatography Overview Applications. Vitamins Overview Fat-Soluble. 

Kiamos, A.A., High-Pressure Phase-Equilibrium Studies of Polymer-Solvent-Supercritical Fluid Mixtures, Masters Essay, The Johns Hopkins University, 1992. 

Solubility of drug and polymer in solvents Supercritical fluid extraction... 

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