Chlorine gas and sodium chlorate are two base chemicals produced through electrolysis of sodium chloride brine which find uses in many areas of industrial chemistry. Although the industrial production of these chemicals started over 100 years ago, there are still factors that limit the energy efficiencies of the processes. This review focuses on the unwanted production of oxygen gas, which decreases the charge yield by up to 5%. Understanding the factors that control the rate of oxygen production requires understanding of both chemical reactions occurring in the electrolyte, as well as surface reactions occurring on the anodes. The dominant anode material used in chlorate and chlor-alkali production is the dimensionally stable anode (DSA), Ti coated by a mixed oxide of RuO2 and TiO2. Although the selectivity for chlorine evolution on DSA is high, the fundamental reasons for this high selectivity are just now becoming elucidated. This review summarizes the research, since the early 1900s until today, conce...

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

In-situ identification of RuO4 as the corrosion product during oxygen evolution on ruthenium in acid media

Selectivity between oxygen and chlorine evolution in the chlor-alkali and chlorate processes : a comprehensive review

A series of alkali- and/or alkali-earth-promoted, carbon-supported Ru catalysts have been prepared by impregnation from aqueous solutions of the precursors. The supports have been pretreated by heating in inert atmosphere at various temperatures, followed by partial oxidation in air at 425°C and then by hydrogen treatment at 900°C. The catalyst samples, diluted 1/22 with quartz powder, have been studied in ammonia synthesis by means of a bench-scale, downflow, continuous, tubular reactor, under standard reaction conditions (430°C, 100 bar total pressure, H2/N2 = 1.5/1 feeding ratio). Caesium and Barium proved to be much more effective promoters than Potassium as promoters and the optimal temperature range for support pretreatment was found to be about 1900°C. The ammonia productivity, on a catalyst volume basis, of our best Ru catalyst was about twice higher than that of the most widely used Fe-based commercial catalysts.

C. Robert Hurley

Papers

Chemistry of Ru(VI), -(VII) and -(VIII). Reactions, Oxidation Potentials and Spectra

Potential of the Ru(VII)-Ri(VIII) Couple