Supercritical fluids SCF

Supercritical Fluid Extraction. Supercritical fluid (SCF) extraction is a process in which elevated pressure and temperature conditions are used to make a substance exceed a critical point. Once above this critical point, the gas (CO2 is commonly used) exhibits unique solvating properties. The advantages of SCF extraction in foods are that there is no solvent residue in the extracted products, the process can be performed at low temperature, oxygen is excluded, and there is minimal protein degradation (49). One area in which SCF extraction of Hpids from meats maybe appHed is in the production of low fat dried meat ingredients for further processed items. Its apphcation in fresh meat is less successful because the fresh meat contains relatively high levels of moisture (50). 

Supercritical Atomization. Atomization can be obtained by mixing a supercritical fluid (SCF) with the material to be atomized. This process reduces volatile organic compound (VOC) emissions as the SCF acts as a solvent and replaces some of the hydrocarbon solvents in the material (see... 

Supercritical fluids (SCFs) have densities similar to those of liquids and a solvent power higher than that of gases, so that compounds which are insoluble in a fluid in ambient conditions become soluble in fluids under supercritical conditions [75]. 

Supercritical fluids (SCFs) are compounds that exist at a temperature and pressure that are above their corresponding critical values [70,71]. They exhibit the properties of both gases and Hquids. With gases, they share the properties of low surface tension, low viscosity, and high diffusivity. Their main Hquid-like feature is the density, which results in enhanced solubility of solutes compared with the solubility of gases. Furthermore, the solubility of solutes can be manipulated by changes in pressure and temperature near the critical point [72]. 

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... 

Table 1. Typical liquid, supercritical fluid (SCF), and gas properties.

Supercritical fluid (SCF) with the beneficial effects of both liquid- and gas-phase chemistry is an emerging reaction medium for many scientific and technical reasons. The reaction rate and selcectivity are readily tunable by a subtle change in pressure and temperature. 

Supercritical fluids (SCFs) are best known through their use for the decaffeination of coffee, which employs supercritical carbon dioxide (scCC ). In this chapter, we will demonstrate that SCFs also have many properties that make them interesting and useful reaction media. Firstly, the physical properties of SCFs will be explained, then the specialist equipment needed for carrying out reactions under high temperatures and pressures will be described. Finally, we will discuss issues relevant to the use of SCFs as solvents for reactions. 

The physical-chemical properties of a supercritical fluid are between those of liquids and gases supercritical fluids (SCFs) indicate the fluid state of a compound in pure substance or as the main component above its critical pressure (pc) and its critical temperature (Tc), but below the pressure for phase transition to the solid state, and in terms of SCF processing, a density close to or higher than its critical density. 

Supercritical fluids (SCFs) offer several advantages as reaction media for catalytic reactions. These advantages include the ability to manipulate the reaction environment through simple changes in pressure to enhance solubility of reactants and products, to eliminate interphase transport limitations, and to integrate reaction and separation unit operations. Benefits derived from the SCF phase Fischer-Tropsch synthesis (SCF-FTS) involve the gas-like diffusivities and liquid-like solubilities, which together combine the desirable features of the gas- and liquid-phase FT synthesis routes. 

A supercritical fluid (SCF) is a substance above its critical temperature and critical pressure. The critical temperature is the highest temperature at which a substance can exist as a gas. The critical pressure is the pressure needed at the critical temperature to liquify a gas. Above the critical temperature and critical pressure, a substance has a density characteristic of a liquid but the flow properties of a gas, and this combination offers advantages as a reaction solvent. The liquidlike density allows the supercritical fluid to dissolve substances, while the gaslike flow properties offer the potential for fast reaction rates. Supercritical carbon dioxide (scC02) has a critical temperature of 31°C and critical pressure of 73 atm. 

Supercritical fluids (SCF) systems, though already established for some applications, may represent more important technologies in the future. The primary motivation for adoption of such processes was concern about and legislation against conventional solvents. 

Isolation Methods. One of the isolation methods evaluated was a liquid-liquid extraction procedure using supercritical fluid (SCF) C02 as the extraction solvent (5). The effectiveness of SCF C02 as an extraction solvent compared to gaseous and liquid C02 is associated with the marked increase in the density of C02 at its critical temperature and pressure, resulting in increased solvating power. The extraction unit that was evaluated was an open system consisting of a SCF C02... 

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