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OwnerOronzio De Nora, Antonio Nidola +1inventors
InventorsOronzio De Nora, Antonio Nidola, Gian N. Martelli
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Halogen is produced by electrolyzing an aqueous halide in a specially designed cell. The cell comprises an anolyte chamber and a catholyte chamber separated by a permeable membrane or diaphragm, notably an ion exchange (generally cation exchange) polymer. At least one electrode comprises at least two sections. One section comprises a gas and electrolyte permeable layer, sheet or mat having a catalytic surface, i.e. one having a low overvoltage, (low hydrogen overvoltage if the cathode and low halogen overvoltage if the anode). This layer is spaced from the membrane by a second section comprising a thin intermediate electroconductive layer, screen or coating which is in contact with the membrane on one side thereof, the other side thereof being in contact with the main cathode. This second or spacer section advantageously has an electrode surface having a higher overvoltage than the first electrode surface. Preferably the cathode has the above construction. Upon electrolysis of alkali metal chloride or other halide in such a cell and with a cathode of the type described above, a low voltage is obtained even at high current densities and the cathode efficiency is high. The spacer may be in the form of a thin porous coating of metal or the like bonded to or in close contact with the membrane or it may be in the form of a gas and electrolyte permeable screen interposed between the membrane and the lower overvoltage section.
A method of generating halogen which comprises electrolyzing an aqueous halide in an electrolytic cell having a pair of opposed electrodes separated by an ion exchange separator at least one of said electrodes having a first electroconductive electrolyte resistant metal screen of relatively low overvoltage and a second electroconductive metal screen of higher overvoltage between the separator and the first metal screen.
A method of generating halogen by electrolysis of aqueous halide which comprises conducting the electrolysis between the anode and cathode separated by an ion exchange membrane wherein the cathode comprises a relatively thick electrolyte permeable cathode section spaced from the membrane by an intervening relatively thin electroconductive metal screen in contact with both the membrane and the relatively thick section, said thin electroconductive metal screen having a higher hydrogen overvoltage than said thick section.
An electrolytic cell comprising a pair of electrodes separated by an ion exchange separator at least one of said electrodes having a first electroconductive electrolyte resistant metal screen of relatively low overvoltage and a second electroconductive surface of higher overvoltage between the separator and the metal screen.
A method of generating halogen, alkali, and hydrogen by electrolysis of aqueous alkali metal halide which comprises conducting said electrolysis in a cell having an anode and a cathode separated by an ion exchange membrane at least one of said electrodes being multilayered and comprising a plurality of open wire mesh screens in electrical contact with each other and having an inner screen adjacent the membrane, said inner screen having a surface of higher overvoltage than an outer screen and in electrical contact therewith, said inner screen being thinner than said outer screen, feeding said solution to the anode, and feeding water to the cathode, and evolving hydrogen and alkali at the cathode.
Dependencies are inferred from the claim text.