ASC Chlor Alkali process makes use of cation exchange membrane technology, which is the most advanced, very efficient and the most environmentally friendly chlor alkali technology producing high quality products fulfilling a wide range of demanding applications. The chlor alkali process involves the electrolysis of aqueous sodium chloride (NaCl solution or brine) in a membrane cell producing chlorine (Cl2) and its co-products caustic soda (sodium hydroxide, NaOH) and hydrogen gas (H2).
In the membrane cell, the anode chamber and cathode chamber are separated by a cation-permeable membrane. Saturated brine (NaCl solution) which consists of Na+ and Cl– ions is fed to the anode chamber.
A DC current is passed through the cell.
At the anode, the chloride ions (Cl–) in brine solution (NaCl) are oxidized to chlorine (Cl2):
And at the cathode, hydrogen ions (H+) in water is reduced to hydrogen gas (H2):
The ion-permeable membrane at the center of the cell plays the important role of allowing the sodium ions (Na+) in the anode chamber to pass to the cathod chamber where they react with the hydroxide ions (OH–) to produce caustic soda (NaOH).
The overall reaction for the electrolysis of brine is thus:
2NaCl (aq) + 2H2O (l) → Cl2 (g) + H2 (g) + 2NaOH (aq)
Another product, sodium hypochlorite (NaClO) is produced when chlorine (Cl2) is reacted with caustic soda (NaOH).
Cl2 + 2 NaOH → NaCl + NaClO + H2O
Because of the corrosive nature of the chlorine produced, the anode has to be made from a non-reactive metal such as titanium, whereas the cathode can be made from Nickel.