Advanced liquid phase processes

Needle-like crystals can readily grow on the surfaces of slowly cooling melts, but they are of no technological and practical significance. Their yield is low, they are difficult to separate from the solid mass and their variable dimensions afford variable properties. In contrast, three new processes afford new short liquid phase-derived semiconductor fibers and novel silver nanotube wires respectively. 

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Results of these investigations demonstrate that changes of the reactor surface can be an effective method for directing chemical reactions. Thus, developing a theory of how heterogeneous factors influence liquid-phase chain reactions is one of the important lines of advancement in this area. Only a few years ago it was thought, almost a priori, that there are practically no heterogeneous factors in liquid-phase oxidation and that liquid-phase processes differ from vapor-phase processes in this respect. 

Another opportunity for advancement in ethylbenzene synthesis is in the development of liquid phase processes that can handle low cost feedstocks, including dilute ethylene such as ethane/ethylene mixtures. The use of dilute ethylene has become increasingly attractive since it has the potential to debottleneck ethylene crackers. Currently higher temperature, vapor phase technologies can tolerate contaminants that enter with the dilute ethylene feed from FCC units. However, these same contaminants can accelerate catalyst aging in lower temperature, liquid phase operations because they are more strongly adsorbed at the lower temperatures. Acid catalysts that tolerate elevated levels of contaminants would facilitate the development of dilute ethylene-based processes. These same catalysts could be useful in applications where lower cost or lower quality benzene feeds are all that are available. 

This book provides the results of research into the development of scientific fundamentals, the technical design and industrial application of brand new technologies and devices for fast liquid-phase turbulent processes in the chemical, petrochemical, and petroleum industries. The macrokinetic approach, considering processes of diffusion, hydrodynamics, and heat transfer, has been developed and used for the advancement of fundamental knowledge and technologically important equations to enable the calculation of mass and heat transfer processes, which accompany fast chemical reactions and well-developed turbulence. This new family of chemical devices has been proposed for the intensification of fast liquid-phase processes through the creation of optimal hydrodynamic conditions for reacting media flows in a reaction zone. 

In summary however, vapor phase processes offer a more effective route to advanced inorganic fibers than solid or liquid phase processes because they facilitate greater control over diameter, length, aspect ratio, and properties of the resulting whiskers, microfibers, and nanotube structures. 

Apart from liquid phase adsorption on a solid adsorbent such as bauxite, the early processes for sweetening and desulfurization were of a chemical nature. Some are in operation today in substantially their original forms, some have been greatly improved, and new processes performing similar functions have been developed. It is beyond the scope of this paper to cover them all, even in outline, therefore a comparative selection has been made to illustrate the advances achieved. The division, which is on a rather arbitrary basis, is given in Table V. 

The Molex process developed by U.O.P. is unique not only in its liquid-phase operation but also in its adsorption system (1-8). Its adsorption system consists of a single adsorption tower with multiple inlet-outlet points and a special rotary valve. The adsorption tower has many smaller adsorption chambers interconnected in series, and it operates under the so-called simulated moving bed operation. Instead of moving the adsorbent bed, the simulated moving bed operates by simultaneously advancing inlet-outlet points periodically. At any time, the adsorber has four zones—viz., adsorption, primary rectification, desorption, and secondary rectification zones, and these zones advance simultaneously as the rotary valve turns periodically. Desorption of n-paraffins is achieved by displacement. 

The process in which a particle dispersed in one phase is overtaken by an advancing interface and surrounded by a second phase. Example when a freezing front (the interface between a solid and its freezing liquid phase) overtakes a particle, the particle will either be pushed along by the front or else be engulfed by the front, depending on its interfacial tensions with the solid and with the liquid. See also Freezing Front Method. 

Computational studies have advanced the study of the solid phase of water and of the interfacial region where the phase transition occurs [1-5]. As water exhibits very unusual properties in the liquid phase, it also exhibits peculiar properties in the solid phase as well. Much about the structure of ice is known from x-ray diffraction experiments or computational studies. Some experiments have been performed on the interfacial region between the liquid and solid phase of water to understand the freezing process, but additional studies are still needed to characterize the... 

The key to the success of the oxidation examples cited above is the ability of the catalysts used to exert proper kinetic control on the possible side reactions. Without it, thermodynamically favorable but undesired products such as CO2 and H2O are made instead. Controlling oxidation kinetics to stop at the desired oxygenated products is quite difficult, and has yet to be solved for many other systems. For instance, although many attempts have been made to develop a commercial process for the oxidation of propylene to propylene oxide, both the activity and the selectivity of the systems proposed to date, mostly based on silver catalysts, are still too low to be of industrial interest " propylene oxide is presently manufactured by processes based on chlorohydrin or hydrogen peroxide instead. In spite of these difficulties, though, recent advances in selective liquid phase oxidation of fine chemicals on supported metal catalysts have shown some promise, offering high yields (close to 100%) under mild reaction conditions." ... 

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