Chlor-alkali process chlorine evolution

As a general rule, these anodes are made from a titanium base metal covered by a rutile layer TiO doped by RuO (30 mol.%). They were used extensively in the industry (e.g., De Nora, Magnetochemie, Permelec, Eltech Systems Corp., US Filter, and Heraeus) and today they are used in all chlor-alkali processes and in chlorate production. The dimensionally stables anodes for chlorine evolution are described in the technical literature by the brand acronyms DSA (RuOj) and DSA -Cl2, and they enjoyed great success in industry for two reasons first, ruthenium has the lowest price of all the PGMs and, second, its density is half that of its neighbors. Moreover, its electrocatalytic characteristics for the evolution of chlorine are satisfactory. In industrial conditions (2 to 4 kA.m ) the service life of these electrodes is over 5 years. Therefore, today, titanium is the only base metal used for manufacturing dimensionally stable anodes for chlorine evolution. The contribution of Beer s discovery to the development of industrial electrochemistry is very important The reader can also find a complete story of the invention of DSA as told by the inventor himself and written on the occasion of his receiving the Electrochemical Society Medal award. 

The last two chapters cover the topics of the production of chlorine and caustic and the phenomena of electrolytic gas evolution. In Chapter 5, Hine et al. describe the engineering aspects of the three processes used in the chlor-alkali industry, and in Chapter 6, Sides reviews the macroscopic phenomena of nucleation, growth, and detachment of bubbles, and the effect of bubbles on the conductivity of and mass transfer in electrolytes. 

The chlorine evolution reaction and the hydrogen evolution reaction at the anode and the cathode, respectively, in a chlor-alkali cell are controlled by the electrochemical and/or chemical steps rather than by mass transfer. However, the transport phenomena across the separator, either a porous diaphragm or an ion-exchange membrane, are governed by the solution flow near the surface. The disproportionation reaction of hypochlorites in a chlorate cell is diffusion-controlled process. Consequently, knowledge... 

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