Caustic soda prodn. by electrolysis of conc. aq. sodium salt soln. - using cell with cation exchange membrane and water as catholyte

摘要

Electrolytic cell for the prodn. of caustic soda from aq. Na salt solns. has a cation exchange membrane, which allows free passage of Na ions by ion exchange. This separates the housing into an anolyte chamber, contg. a conc. aq. Na salt soln.., and a catholyte chamber, contg. water. It has a pair of electrodes, >=1 and pref. both of which is a catalyst electrode, consisting of a composite mixt. of hydrophobic particles and noble metal catalyst particles, which is bound to the surface of the membrane and embedded in it. The cell is connected to a d.c. supply and the voltage is high enough for the electrolysis of the water in the Na salt soln. to produce oxygen and Na cations and of the catholyte to produce hydrogen gas and OH ions. The energy consumption is lower than usual and the NaOH obtd. has a high degree of purity.