Production of halogens by electrolysis of alkali metal halides in an electrolysis cell having catalytic electrodes bonded to the surface of a solid polymer electrolyte membrane

In the process of generating halogen and alkali metal hydroxide by electrolysis of aqueous alkali metal halide containing at least 150 grams of halide per liter of solution by means of a pair of catalytic electrodes separated by an ion permeable membrane, the improvement which comprises conducting the electrolysis with an electrode comprising a plurality of thermally stabilized, reduced oxide particles of platinum group metals bonded to and embedded in the cathodic side of the membrane.

A process for generating chlorine by electrolyzing an aqueous alkali metal chloride with a minimum concentration of 150 grams of chloride per liter of solution between anode and cathode electrodes separated by an ion exchange membrane which restrains flow of aqueous electrolyte therethrough, which comprises conducting said electrolysis with a cathode comprising a thin layer of electrochemically active particles of a material of the group consisting essentially of a platinum group metal and/or conductive oxides thereof, said layer being bonded to one side of said membrane to form a unitary membrane-electrode and in contact with a current distributor exposed to the electrolyte and having a hydrogen overvoltage higher than said cathode layer of particles.

A process of generating chlorine by electrolyzing an aqueous alkali metal chloride having a minimum concentration of 150 grams of chloride per liter of solution between an anode and a cathode separated by an ion exchange membrane which restrains flow of aqueous electrolyte therethrough, which comprises conducting the electrolysis with an anode comprising a thin layer of electrochemically active particles, consisting essentially of platinum group metals and/or conductive oxides thereof, said layer being in contact with and bonded to one side of the membrane to form a unitary membrane electrode and in contact with a current distributor exposed to said aqueous alkali metal chloride and having a surface of higher chlorine overvoltage than said anode layer of particles.

In a process for generating halogens and alkali hydroxides which comprises electrolyzing an aqueous alkali metal halide between an anode and a cathode electrode separated by a polymeric cation exchange membrane, at least one of the electrodes comprising plurality of electroconductive catalytic particles bonded to and embedded in said membrane to provide a gas and electrolyte permeable electrode, wherein the cathode side of said membrane has a lower water content than the remaining portion to provide an anion barrier which rejects the hydroxyl ions and minimizes diffusion of the alkali across the membrane to the anode electrode.

A process of generating chlorine which comprises electrolyzing aqueous alkali metal chloride at least 2.5 molar in concentration between a pair of gas permeable electrodes comprising an anode and cathode separated by a cation exchange membrane, the electrochemically active area of at least one of said electrodes being electrochemically active particles directly bonded to the membrane whereby ionic current may flow directly between the electrodes and the membrane without passage through an intervening body of fluid electrolyte, maintaining the anode in contact with alkali metal chloride at least 2.5 molar in concentration and maintaining the cathode in contact with aqueous alkali.

A process of generating chlorine which comprises electrolyzing an aqueous chloride containing at least 150 grams of chloride per liter of solution between anode and cathode separated by an ion exchange membrane, the cathode being a layer of electrochemically active particles bonded to the membrane to form a unitary electrode membrane structure and supplying potential to the cathode by a current distributor which has an electronically conductive surface in contact with the cathode and is exposed to the catholyte, said cathode having a lower hydrogen overvoltage than the electroconductive current distributor surface.

A process of generating chlorine which comprises electrolyzing an aqueous chloride containing at least 150 grams of said chloride per liter of solution between a cathode separated from the anode by an ion exchange membrane, the anode being electrochemically active particles bonded to the membrane, supplying potential to the anode by a current distributor which has an electroconductive surface which contacts the anode and is exposed to the chloride electrolyte, said anode having a lower chlorine overvoltage than the current distributor.

A process of generating chlorine which comprises feeding aqueous alkali metal chloride containing at least 150 grams of alkali metal chloride per liter of solution into the anode compartment of an electrolytic cell having anode and cathode compartments separated by a cation exchange membrane having gas permeable layers of electrolytically resistant, electrochemically active, electrode particles bonded together and to opposite sides of the membrane, the membrane and its layers being sandwiched between and in contact with a pair of electroconductive current distributors having surfaces resistant to ttack by electrolyte to which they are exposed, applying a potential of opposite polarity to said current distributors, maintaining aqueous alkali metal chloride of at least said chloride concentration in contact with the anode and maintaining an alkaline solution in contact with the cathode.

A process for generating chlorine which comprises electrolyzing an aqueous alkali metal chloride containing at least 2.5 molar chloride concentration between a pair of opposed electrodes comprising anode and cathode separated by an ion exchange membrane at least one of said electrodes bonded directly to the membrane to form a unitary membrane electrode structure, said electrode comprising a particulate mixture of graphite and a platinum group metal and/or oxide thereof.