Method for electrolysis of aqueous alkali metal chloride solution

Claim 1

In a process for the electrolysis of an aqueous alkali metal chloride solution in an electrolytic cell divided by a cation-exchange membrane, through which neither liquid nor gas can substantially pass, into an anode compartment and a cathode compartment, respectively, to produce alkali metal hydroxide and discharging hydrogen gas and chlorine gas from the cathode compartment and the anode compartment, respectively, the improvement which comprises utilizing a cathode which is joined with said cation-exchange membrane throughout one entire side surface thereof wherein said cation-exchange membrane has a powdered cathodic substance uniformly and densely embedded in the cathode side surface of the membrane and positioning and maintaining an anode of porous construction in close proximity to but not in contact with the other side surface of the membrane through which neither liquid nor gas can substantially pass wherein electrolysis is carried out at a high current density of not less than 20 A/dm 2 , the concentration of alkali hydroxide in the catholyte is maintained in a range of from 15 to 45% by weight and wherein the oxygen gas content of the chlorine gas is not more than 0.6% by volume.