Einsatz perfluorierter Kationenaustauscher-Membranen in Elektroyseverfahren,insbesondere bei der Chloralkali-Elektrolyse

Use of perfluorinated cation exchanger membranes in electrolysis processes, particularly in alkali chloride electrolysis . Depending upon their structure, texture, and possible after-treatment, the properties of perfluorinated cation exchanger membranes show variations and their use has consequently been limited to electrolyses in aqueous solutions and indirect organic syntheses. With regard to equipment, the membranes open up new techniques, extending beyond conventional two- and multi-compartment cells, which have become known as solid polymer electrolysis (SPE) and oxygen consuming cathode (OCE). Applications of the membranes, which are resistent to oxidizing acids and alkalies, are considered in the cases of alkali chloride electrolysis, soda production, decomposition of water, electrolysis of hydrochloric acid, and electrochemical synthesis of propylene oxide. Concepts of the relationships governing OH^? ion migration through the membrane and the associated problems are essential if membrane cells are to be operated economically. Only in this way can the operating conditions be chosen optimally and the specific concentration-dependent properties of the membranes be fully exploited by chemical reaction engineering modifications, e.g. by a countercurrent cascade arrangement. Granted comparable economics the advantages of membrane equipment over conventional processes lie in a reduced environmental burden and possibly far lower energy consumption (which, however, may have to be bought at the price of additional investment). These advantages may be offset by the detrimental foreign ion content of the electrolyte, possible low current density, undesired by-product formation, back-diffusion processes, limited lifetime, combined with the high price of the membranes and the low maximum area of the individual cell; solution of these latter problems will further enhance performance.