Chlorate, production, dimensionally stable anodes

Chlorate, production, dimensionally stable anodes, 40 102-103 Chlorides catalysts, 40 50... 

Platinum Platinum-coated titanium is the most important anode material for impressed-current cathodic protection in seawater. In electrolysis cells, platinum is attacked if the current waveform varies, if oxygen and chlorine are evolved simultaneously, or if some organic substances are present Nevertheless, platinised titanium is employed in tinplate production in Japan s. Although ruthenium dioxide is the most usual coating for dimensionally stable anodes, platinum/iridium, also deposited by thermal decomposition of a metallo-organic paint, is used in sodium chlorate manufacture. Platinum/ruthenium, applied by an immersion process, is recommended for the cathodes of membrane electrolysis cells. ... 

Kalu and Oloman [75] studied the simultaneous synthesis of alkaline hydrogen peroxide and sodium chlorate in a bench-scale flow-by single-cell electrochemical reactor. A schematic of the electrode conditions is shown in Fig. 18. Graphite felt was used as the cathode to synthesize peroxide from 0.5 -2.0 M NaOH chlorate was the product at a dimensionally stable anode (DSA). The anodic and cathodic reactions were as follows ... 

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. 

Dimensional stable anodes (DSAs). The unique electrochemical properties of the titanium DSA make it the most energy efficient unit for the production of chlorine, chlorate, and hypochlorite. 

Ruthenium is not as industrially important as other noble metals, but it is used as Ru02 to coat the dimensionally stable titanium anodes used in the production of chlorine, chlorate, and caustic, as well as oxygen in water electrolysis. Ruthenium has also found some use as a binder for high-temperature cemented carbides. 

---