Supercritical fluid (SCF) has been given much attention as a "new-type solvent" in various fields of industry. Micro- and macro-properties of SCF are reviewed and their advantageous points are noted. New application fields of SCF are remarked.
Supercritical fluids vary in density from that over a whole range by manipulating temperature and pressure. One of the characteristic features of supercritical fluids is “clustering/solvation” or “local density augmentation, ” which is due to solute/solvent intermolecular interaction. This paper presents the results reported in recent experimental and theoretical works on clus-tering, intermolecular interactions and aggregate formation. In addition, recent publications about the partial molar volume and dielectric constant are also presented.
Typical solubility behavior in supercritical fluids (SCF) has been described in terms of density effects, functional group, and entrainer effects. Phase diagrams of SCF are reviewed for binary mixtures with and without solid phases, by showing typical three-dimensional phase diagrams. Pressure - composition diagrams in SCF are classified from the view point of good and poor solvents. The thermodynamic stability analysis is shown for illustration of complex phase behavior of SFC including vapor-liquid, liquid-liquid, solid-vapor, or solid-liquid equilibria. The historical view of the mixing rules in equations of state of mixtures is outlined. Computer simulation techniques and their role on SCF are touched on.
The applications of supercritical fluids to separation and purification processes are reviewed. Supercritical fluid processes have been mainly applied in food and pharmaceutical industry. Principles and recent applications of supercritical fluid process including retrograde crystallization and rectification column are described.
The objective of this paper is to present a review of the field of reactions in supercritical fluids (SCF). Significant solvent effects on the reaction rate and the reaction equilibrium constant around the critical point and the supercritical region are discussed. Then a variety of applications of supercritical fluids to reaction processes, including coal extraction, biomass hydrolysis in supercritical water (SCW), rapid oxidation in SCW, solid catalyzed reactions, enzymatic reactions, and hydrothermal crystallization in SCW, were introduced.
This paper provides an overview of the applications of supercritical fluid technologies to the production and the processing of materials. The novel physical and chemical properties of supercritical fluids are related to their use as extraction solvents, crystallization solvents and reaction media. Supercritical debindering or drying technologies aviod cracks and shrinkage of molded porous materials. The RESS (rapid expansion of supercritical solutions) method, the GAS (gas antisolvent) recrystallization method and hydrothermal processes provide techniques for producing fine uniform powders, thin films and fibers of widely varying materials.
Fundamental characteristics of supercritical fluid chromatography (SFC) and analytical supercritical fluid extraction (SFE) are described. SFC is a powerful technique for separating non-volatile and thermally labile compounds which can not be separated by gas chromatography. In addition, SFC has advantages of higher chromatographic efficiencies and detection versatility compared to liquid chromatography. SFE has many advantages over conventional liquid extraction, such as the potential of rapid and selective extraction. One unique feature of SFE is that it can be easily interfaced to chromatographic techniques.
In this review, we outline the application of Raman spectroscopic measurements to high pressure researches. Raman spectroscopic measurements provides a useful means of investigating phase transformations because its spectral structure is closely related to the atomic arrangement in the crystal. Recently, Raman spectral measuring systems with high sensitivity are developed by using liquid nitrogen cooled CCD camera. Combining these Raman measuring systems with diamond anvil cell, Raman spectroscopic measurement under high pressure provides a useful means to investigate the crystal structure of unknown high pressure phase. The Raman spectroscopic studies for high pressure phases of TiO2 and ZrO2 are reviewed.
Crystal growth mass is proportional to an area of a crystal surface. For producing a large diamond single crystal within a short time, we tried to use a large single seed crystal to obtain a single crystal immedately on it by the Temperature Gradient Method. A large single crystal, ten-carat size, was obtained within a short time, but many metal solvent inclusions were not removed in the above-mentioned seed crystal. The distribution of inclusions was relatee to morphologies. When a crystal grows into a hexagonal shape, a density of inclusions is minimized.
Japan has fully opened its market to overseas fruit juice suppliers as from April 1, 1991, after experiencing very strict import restrictions implemented after the world war II. This change is affecting substantially the Japanese fruit juice industry which has been heavily relied on mandarin juice, made from locally grown satsuma mandarin fruit and juice diluted products rather than 100 % juice. Citrus juice occupied about 50 % of the total juice consumed in 1992 and 100 % consumption in the same year reached 34 % of juice market share. As more imported sweet orange and other juices and more 100 % juice consumption is expected, the local satsuma mandarin fruit growers and mandarin juice manufactures meet with difficulties. Mandarin juice is very heat sensitive, bringing unfavorable flavor once it is heattreated. In order to overcome this chemical change, we have developed a special sterilization process by the use of ultra high pressure, which requires practically no heat. After making some tests during 1991/1992 mandarin crop season, we went into the commercial production of satsuma mandarin juice in the 1992/1993 season.