Controlled operation of high current density oxygen consuming cathode cells to prevent hydrogen formation

摘要

A process for the electrolysis of an alkali metal halide brine is operated in an electrolytic cell having an anode compartment containing at least one anode, a cathode compartment containing at least one cathode, and a cation exchange membrane separating the anode compartment from the cathode compartment. The process comprises:P P(a) feeding the alkali metal halide brine to the anode compartment;PP (b) electrolyzing the alkali metal halide brine at a current density of at least about 2 kiloamperes per square meter to produce a halogen gas and alkali metal ions in the anode compartment;PP(c) passing the alkali metal ions and water through the cation exchange membrane into the cathode compartment wherein contact is maintained between the cation exchange membrane and the hydrophilic porous cathode; PP(d) feeding an oxygen- containing gas to the cathode compartment;PP(e) producing a concentrated alkali metal hydroxide solution while limiting the formation of hydrogen; andP P(f) removing the concentrated alkali metal hydroxide solution from the cathode compartment to prevent an accumulation of concentrated alkali metal hydroxide in the cathode compartment.PP Operation of the process of the present invention is free of the restrictions for hydrostatic pressures and gas pressures required when hydrophobic cathode materials are used in the cathode compartment. The process further permits the use of increased current densities without forming significant amounts of hydrogen gas.