Solution-liquid-solid process

Solution-Liquid-Solid Process Buhro and coworkers [276], have developed a low temperature solution-liquid-solid (SLS) method for the synthesis of highly crystalline nanowires of III-V semiconductors [276, 327]. In a typical procedure, a metal (e.g., In, Sn, Bi) with a low melting point was used as a catalyst, and the de-... 

The most important nanomaterial synthesis methods include nanolithography techniques, template-directed syntheses, vapor-phase methods, vapor-liquid-solid (VLS) methods, solution-liquid-solid (SLS) approaches, sol-gel processes, micelle, vapor deposition, solvothermal methods, and pyrolysis methods [1, 2]. For many of these procedures, the control of size and shape, the flexibility in the materials that can be synthesized, and the potential for scaling up, are the main limitations. In general, the understanding of the growth mechanism of any as-... 

In liquid-solid processes reaction takes place between a liquid reactant and an insoluble or sparingly soluble solid which must be finely divided to speed up the process. Another measure to accelerate the process is to use an aqueous solution of a phase-transfer agent (typically a quaternary ammonium salt). The solid can also be a catalyst for reactions between liquid components, e.g. in acylations, carried out both conventionally in the presence of metal chlorides (mostly AICI3) or catalysed by zeolites and Grignard reactions. 

To examine a sample by inductively coupled plasma mass spectrometry (ICP/MS) or inductively coupled plasma atomic-emission spectroscopy (ICP/AES) the sample must be transported into the flame of a plasma torch. Once in the flame, sample molecules are literally ripped apart to form ions of their constituent elements. These fragmentation and ionization processes are described in Chapters 6 and 14. To introduce samples into the center of the (plasma) flame, they must be transported there as gases, as finely dispersed droplets of a solution, or as fine particulate matter. The various methods of sample introduction are described here in three parts — A, B, and C Chapters 15, 16, and 17 — to cover gases, solutions (liquids), and solids. Some types of sample inlets are multipurpose and can be used with gases and liquids or with liquids and solids, but others have been designed specifically for only one kind of analysis. However, the principles governing the operation of inlet systems fall into a small number of categories. This chapter discusses specifically substances that are normally liquids at ambient temperatures. This sort of inlet is the commonest in analytical work. 

Theoretical and applied aspects of microwave heating, as well as the advantages of its application are discussed for the individual analytical processes and also for the sample preparation procedures. Special attention is paid to the various preconcentration techniques, in part, sorption and extraction. Improvement of microwave-assisted solution preconcentration is shown on the example of separation of noble metals from matrix components by complexing sorbents. Advantages of microwave-assisted extraction and principles of choice of appropriate solvent are considered for the extraction of organic contaminants from solutions and solid samples by alcohols and room-temperature ionic liquids (RTILs). 

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

Liquid-solid chromatography (LSC). This process, often termed adsorption chromatography, is based on interactions between the solute and fixed active sites on a finely divided solid adsorbent used as the stationary phase. The adsorbent, which may be packed in a column or spread on a plate, is generally a high surface area, active solid such as alumina, charcoal or silica gel, the last... 

Sorbitol is produced by a gas-liquid-particle process in which a solution of glucose is hydrogenated in the presence of a solid catalyst consisting of nickel on diatomaceous earth carrier (B6). 

Life as we know it depends on this existence of water as a liquid. Biochemical processes require free movement of chemicals, which cannot occur in the solid phase. Biochemical stmctures contain many interlocking parts that would not be stable in the gas phase. Thus, the liquid phase is best suited for life. Moreover, water is an excellent solvent, particularly for molecules that can form hydrogen bonds. As we describe in Chapter JA, the molecular building blocks of living matter are rich in groups that form hydrogen bonds. This allows biological molecules to be synthesized, move about, and assemble into complex structures, all in aqueous solution. 

Adsorption is a physicochemical process whereby ionic and nonionic solutes become concentrated from solution at solid-liquid interfaces.3132 Adsorption and desorption are caused by interactions between and among molecules in solution and those in the structure of solid surfaces. Adsorption is a major mechanism affecting the mobility of heavy metals and toxic organic substances and is thus a major consideration when assessing transport. Because adsorption is usually fully or partly reversible (desorption), only rarely can it be considered a detoxification process for fate-assessment purposes. Although adsorption does not directly affect the toxicity of a substance, the substance may be rendered nontoxic by concurrent transformation processes such as hydrolysis and biodegradation. Many chemical and physical properties of both aqueous and solid phases affect adsorption, and the physical chemistry of the process itself is complex. For example, adsorption of one ion may result in desorption of another ion (known as ion exchange). 

Low temperature. Low-temperature processes (below 0°C) contain large amounts of fluids kept in the liquid state by pressure and/or low temperature. If for any reason it is not possible to keep them under pressure or keep them cold, then the liquids will begin to vaporize. If this happens, impurities in the fluids are liable to precipitate from solution as solids, especially if equipment is allowed to boil dry. Deposited solids may not only be the cause of blockage but also in some cases the cause of explosions. It is necessary, therefore, to ensure that the fluids entering a low-temperature plant are purified. A severe materials-of-construction problem in low-temperature processes is low-temperature embrittlement. Also, in low temperature as in high-temperature operations, the equipment is subject to thermal stresses, especially during start-up and shutdown. 

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