Oronzio Denora Impianti Elettrochimici S.p.a.

Raymond S Chisholm

Bjorn Holmstrom

Chlorine and other halogens can be generated by electrolyzing an aqueous alkali metal halide or hydrogen halide between an anode and cathode in an electrolytic cell having a composite semipermeable membrane separating the said electrodes. This membrane is in sheet form and normally comprises a layer, coating or sheet of a fluorocarbon having cation exchange groups disposed on the anode side and a second layer, coating or sheet on the cathode side which is non-fluorinated or is less fluorinated and consequently more hydrophilic (less hydrophobic) than the first layer and which also has cation exchange groups i.e. acid groups or alkali metal salts thereof attached thereto. The less fluorinated cathodic side apparently releases evolved hydrogen more readily than does the more heavily fluorinated anode layer, particularly when the cathode is in contact with or bonded to and/or embedded in the membrane. The cathode is maintained close enough to the cathode side of the membrane to maintain the more hydrophilic second layer alkaline during the electrolysis and the two layers may be bonded together or may be installed together and in contact with each other without bonding.

Electrolytic cell and method

In an electrolytic cell comprising a cell unit with at least one anodic compartment equipped with an anode and at least one cathodic compartment equipped with a cathode, said compartments being separated by a diaphragm comprised of at least two separable layers of electrolyte impermeable, ion permeable material in contact with each other, the said layers being unbonded or weakly bonded together so they are capable of being separated or one of the layers having been at least partially preswelled before bonding and a method of electrolysis with said cells, especially for electrolysis of an aqueous electrolyte containing halide ions to produce halogen.

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Pittsburgh, PA, United States of America

Raymond S Chisholm