Selectivity between Oxygen and Chlorine Evolution in the Chlor-Alkali and Chlorate Processes

Area of Science:

• Electrochemistry
• Industrial Chemistry
• Materials Science

Background:

• Chlorine gas and sodium chlorate are vital industrial chemicals produced via sodium chloride brine electrolysis.
• Current production processes face energy efficiency limitations due to unwanted oxygen gas formation, reducing charge yield by up to 5%.

Purpose of the Study:

• To review historical and current research on oxygen evolution selectivity in chlorate and chlor-alkali production.
• To elucidate factors controlling oxygen production rates on anodes.

Main Methods:

• Comprehensive review of experimental and theoretical studies from the early 1900s to present.
• Analysis of anode materials, specifically dimensionally stable anodes (DSA) with RuO2 and TiO2 coatings.
• Investigation of electrolyte chemistry and process conditions impacting selectivity.

Main Results:

• Dimensionally stable anodes (DSA) exhibit high selectivity for chlorine evolution, though the underlying mechanisms are still being clarified.
• Process conditions, electrolyte composition, and anode material properties significantly influence the selectivity between chlorine and oxygen evolution.
• Understanding these factors is crucial for optimizing energy efficiency.

Conclusions:

• Further research into the fundamental reasons for high chlorine selectivity on DSA is needed.
• Optimizing process parameters and anode characteristics can mitigate oxygen evolution and enhance industrial chemical production efficiency.