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Synthesizing research from a wide variety of sources, this work offers a convenient guide to a clean, safe, inexpensive, non-toxic, non-polluting solvent that performs better than most conventional solvents. Natural Extracts Using Supercritical Carbon Dioxide reviews recent developments in the technology and its applications to the food, flavor, fragrance, and pharmaceutical industries. It outlines the many advantages that this method has over traditional methods like steam distillation, solvent extraction, and molecular distillation, and it supports the popular trend toward the use of natural products in these industries.
Enhanced concern for the quality and safety of food products, increased preference for natural products, and stricter regulations on the residual level of solvents, all contribute to the growing use of supercritical fluid technology as a primary alternative for the extraction, fractionation, and isolation of active ingredients. As a solvent-free p
Supercritical fluids are neither gas nor liquid, but can be compressed gradually from low to high density and they are therefore interesting and important as tunable solvents and reaction media in the chemical process industry. By adjusting the density the properties of these fluids can be customised and manipulated for a given process - physical or chemical transformation. Separation and processing using supercritical solvents such as CO2 are currently on-line commercially in the food, essential oils and polymer industries. Many agencies and industries are considering the use of supercritical water for waste remediation. Supercritical fluid chromatography represents another, major analytical application. Significant advances have recently been made in materials processing, ranging from particle formation to the creation of porous materials. The chapters in this book provide tutorial accounts of topical areas centred around: (1) phase equilibria, thermodynamics and equations of state; (2) critical behaviour, crossover effects; (3) transport and interfacial properties; (4) molecular modelling, computer simulation; (5) reactions, spectroscopy; (6) phase separation kinetics; (7) extractions; (8) applications to polymers, pharmaceuticals, natural materials and chromatography; (9) process scale-up.
Sample preparation is an essential step in many analyses. This book approaches the topic of sample preparation in chromatography in a methodical way, viewing it as a logical connection between sample collection and analytical chromatography. Providing a guide for choosing the appropriate sample preparation for a given analysis, this book describes various ways to process the sample, explaining the principle, discussing the advantages and disadvantages, describing the applicability to different types of samples, and showing the fitness to specific chromatographic determinations. The first part of the book contains an overview of sample preparation showing its relation to sample collection and to the core chromatographic analysis. The second part covers procedures that do not use chemical modifications of the analyte and includes methods for sample dissolution, concentration and cleanup designed mainly for modifying the initial matrix of the sample. This part starts with conventional separations such as filtration and distillation and finishes with more advanced techniques such as solid phase extraction and electroseparations. The third part gives a description of the chemical modifications that can be performed on a sample either for fractionation purposes or to improve a specific property of the analyte. This part includes derivatizations, polymer chemical degradations, and pyrolysis.
Application of compressed gases as solvents has found widespread interest within the scientific community. Its processes have industrial applications. Gas Extraction deals with the possibilities of supercritical gases as solvents for separation processes. The volume combines physico-chemical aspects with chemical engineering methods. The text generalizes as far as possible, and treats examples in detail. Gas Extraction covers, for the first time, the subject in textbook form. Most of the examples provide new results that will be helpful for practicing scientists, engineers, and students who want to make use of the techniques.
Supercritical fluids which are neither gas nor liquid, but can be compressed gradually from low to high density, are gaining increasing importance as tunable solvents and reaction media in the chemical process industry. By adjusting the pressure, or more strictly the density, the properties of these fluids are customized and manipulated for the particular process at hand, be it a physical transformation, such as separation or solvation, or a chemical transformation, such as a reaction or reactive extraction. Supercritical fluids, however, differ from both gases and liquids in many respects. In order to properly understand and describe their properties, it is necessary to know the implications of their nearness to criticality, to be aware of the complex types of phase separation (including solid phases) that occur when the components of the fluid mixture are very different from each other, and to develop theories that can cope with the large differences in molecular size and shape of the supercritical solvent and the solutes that are present.
The potential of supercritical fluid methods is presented in a comprehensive way. On the basis of a careful discussion of physical and chemical principles, the application of this method in process technology is demonstrated.
Traditionally, the teaching of phase equilibria emphasizes the relationships between the thermodynamic variables of each phase in equilibrium rather than its engineering applications. This book changes the focus from the use of thermodynamics relationships to compute phase equilibria to the design and control of the phase conditions that a process needs. Phase Equilibrium Engineering presents a systematic study and application of phase equilibrium tools to the development of chemical processes. The thermodynamic modeling of mixtures for process development, synthesis, simulation, design and optimization is analyzed. The relation between the mixture molecular properties, the selection of the thermodynamic model and the process technology that could be applied are discussed. A classification of mixtures, separation process, thermodynamic models and technologies is presented to guide the engineer in the world of separation processes. The phase condition required for a given reacting system is studied at subcritical and supercritical conditions. The four cardinal points of phase equilibrium engineering are: the chemical plant or process, the laboratory, the modeling of phase equilibria and the simulator. The harmonization of all these components to obtain a better design or operation is the ultimate goal of phase equilibrium engineering. - Methodologies are discussed using relevant industrial examples - The molecular nature and composition of the process mixture is given a key role in process decisions - Phase equilibrium diagrams are used as a drawing board for process implementation
The use of supercritical fluids in analytical chemistry is still grow ing. More and more analysts are discovering the favorable advan tages for a number of applications. Especially supercritical fluid extraction (SFE) has attracted a lot of interest in recent years due to its simplicity. Supercritical fluid chromatography (SFC) has become better established and the development of this technique has been accelerated by the many applications with capillary col umns which have been published in the literature. At first SFC equipment was based on instruments commonly used for liquid chromatography, and the first commercial in struments were derived from this technology. However, capillary columns can be much more easily interfaced to gas chromatogra phy equipment especially to the detectors commonly used for Oc. Many stationary phases both for packed micro columns and capillary columns have been designed for SFC purposes extending this technology to LC and OC. The most common fluid applied in SFC and SFE is carbon dioxide. The advantages of supercritical CO , such as having dif 2 fusivity like a gas and solvating power depending on temperature and pressure, are also valid for other fluids and modified fluids. Both properties are valuable for sample extraction and extraction selectivity.
The continued search for rapid, efficient and cost-effective means of analytical measurement has introduced supercritical fluids into the field of analytical chemistry. Two areas are common: supercritical fluid chroma tography and supercritical fluid extraction. Both seek to exploit the unique properties of a gas at temperatures and pressures above the critical point. The most common supercritical fluid is carbon dioxide, employed because of its low critical temperature (31 °C), inertness, purity, non-toxicity and cheapness. Alternative supercritical fluids are also used and often in conjunction with modifiers. The combined gas-like mass transfer and liquid-like solvating characteristics have been used for improved chroma tographic separation and faster sample preparation. Supercritical fluid chromatography (SFC) is complementary to gas chro matography ( GC) and high performance liquid chromatography (HPLC), providing higher efficiency than HPLC, together with the ability to analyse thermally labile and high molecular weight analytes. Both packed and open tubular columns can be employed, providing the capability to analyse a wide range of sample types. In addition, flame ionization detection can be used, thus providing 'universal' detection.