Electrochemistry commercial processes

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

The starting material for all industrial chlorine chemistry is sodium chloride, obtained primarily by evaporation of seawater. The chloride ion is highly stable and must be oxidized electrolytically to produce chlorine gas. This is carried out on an industrial scale using the chlor-alkali process, which is shown schematically in Figure 21-15. The electrochemistry involved in the chlor-alkali process is discussed in Section 19-. As with all electrolytic processes, the energy costs are very high, but the process is economically feasible because it generates three commercially valuable products H2 gas, aqueous NaOH, and CI2 gas. 

The lag between the time that nitinol, was first produced and the time it was used commercially in medical devices was due in part to the fear that nickel would leach from the metal and not be tolerable as a human implant. As it turns out, with a correct understanding of the surface electrochemistry and subsequent processing, a passivating surface layer can be induced by an anodizing process to form on the nitinol surface. It is comprised of titanium oxide approximately 20 mn thick. This layer actually acts as a barrier to prevent the electrochemical corrosion of the nitinol itself. Without an appreciation for the electrochemistry at its surface, nitinol would not be an FDA-approved biocompatible metal and an entire generation of medical devices would not have evolved. This is really a tribute to the understanding of surface electrochemistry within the context of implanted medical devices. 

This chapter is devoted to the subject matter of electrochemistry in the service of, and how it relates to, medicine. It is indeed timely for this kind of topic to be discussed in a book such as this one. Medicine is the second-oldest profession, and as such, alone deserves our closer attention. Further, in the ongoing process of globalization, we are witnessing not only the tendency of commercial unification of the globe but the rapidly emerging interdependency of different scientific and technical disciplines as well. 

Molten salts or ionic liquids (also referred to as fused salts by some authors) were among the very first media to be employed for electrochemistry. In fact, Sir Humphrey Davy describes electrochemical experiments with molten caustic potash (KOH) and caustic soda (NaOH) [1] as early as 1802 A wide variety of single molten salts and molten salt mixtures have been used as solvents for electroanalytical chemistry. These melts run the gamut from those that are liquid well below room temperature to those melting at more than 2000°C. The former present relatively few experimental challenges, whereas the latter can present enormous difficulties. For example, commercially available Teflon- and Kel-F-shrouded disk electrodes and Pyrex glass cells may be perfectly adequate for electrochemical measurements in ambient temperature melts such as the room-temperature chloroaluminates, but completely inadequate for use with molten sodium fluoroaluminate or cryolite (mp = 1010°C), which is the primary solvent used in the Hall-Heroult process for aluminum electrowinning. 

There is no doubt that catalytic asymmetric synthesis has a significant advantage over the traditional diastereomeric resolution technology. However, it is important to note that for the asymmetric hydrogenation technology to be commercially useful, a low-cost route to the precursor olefins is just as crucial. The electrocarboxylation of methyl aryl ketone and the dehydration of the substituted lactic acids in Figures 5 and 6 are highly efficient. Excellent yields of the desired products can be achieved in each reaction. These processes are currently under active development. However, since the subjects of electrochemistry and catalytic dehydration are beyond the scope of this article, these reactions will be published later in a separate paper. 

To start with, it is advisable to do pilot-plant experiments in a standard (commercial) cell and use standard electrochemical equipment. Don t try to optimize the electrochemistry first, but try to minimize the outlay for the whole process. 

The oldest process of organic electrochemistry is the indirect oxidation of hydrocarbons with chromic acid. It has been employed industrially for more than 90 years by Hoechst— now Clariant—in Gersthofen, Germany [102]. Other sites are or were located in Great Britain. The oxdiations of naphthalene, anthracene, and camphene are examples. Companies like Emery Industries, L. B. Holliday, and Boots have also used chromic acid regeneration commercially [103]. It has been employed for the bleaching of montan waxes for more than 70 years. 

In recent years, a number of electrolytic processes have utilized membranes in producing both anodic and cathodic products. By far, however, the most important application of this technology has been in the chlor-alkali industry. Intense commercial and academic interest has been focused into this field during the past decade so that ion exchange theory as applied to membranes is in a more advanced state than any of the other ion exchange systems. The primary examples of industrial chlor-alkali electrochemistry are found in the production of chlorine, caustic soda and potash, hydrogen and hypochlorite (1) (4). 

In this context, nanoporous carbons are extremely interesting materials which can be used either as electrodes of supercapacitors or hydrogen reservoir. They are commercially available at a low cost and under various forms (powder, fibers, foams, fabrics, composites) [3]. They can be obtained with well-developed and controlled porosity [4,5] and with a rich surface functionality [6,7], As far as electrochemistry applications are concerned, very important advantages of carbons are a high electrical conductivity, a good chemical stability in various electrolytic media and the possibility to control wettability by the nature of the surface functionality. When they are not playing the role of active material for the storage process, carbons may be also useful as additive in a composite to improve its physical properties. Particularly carbon nanotubes are able to improve the electrical conductivity and mechanical properties of electrodes [8],... 

In this chapter a detailed CFD study of the chemical and electrochemical processes in an internally reforming anode supported SOFC button cell was carried out. Detailed models for chemistry, electrochemistry and porous media transport have been implemented into the commercial CFD code FLUENT with the help of used defined functions (UDF). Simulation results were compared with experimentally reported data. The comparisons lead to the conclusion that precise calculation of surface carbon formation is critical for the accurate prediction of OCVs for hydrocarbon fuels with very low H2O content, and that Nemst equation may not be valid for the calculation of OCV for a fuel composition such as the one considered here. Anodic overpotentials showed remarkable difference from expected behavior. 

Boron incorporated during a chemical vapor deposition (CVD) process is now proving to be the most popular means of imparting electrical conductivity on the diamond lattice for use in electrochemistry, both from a research perspective and commercially, for reasons that will be discussed later. There have been many reviews since 1983, both in journals [2-9] and books [10] on the use of diamonds in electrochemistry. This chapter aims to review the field and provide a comprehensive discussion on the current understanding of the fundamental factors controlling the response of boron-doped diamond (BDD) electrodes. Latest developments (as of 2014) are also highlighted. 

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