History of the Chlor-Alkali Industry

During the last half of the 19th century, chlorine, used almost exclusively in the textile and paper industry, was made [1] by reacting manganese dioxide with hydrochloric acid 

Recycling of manganese improved the overall process economics, and the process became known as the Weldon process [2], In the 1860s, the Deacon process, which generated chlorine by direct catalytic oxidation of hydrochloric acid with air according to Eq. (2) was developed [3], 

Utilization of HCl from reaction (3) eliminated the major water and air pollution problems of the LeBlanc process and allowed the generation of chlorine. By 1900, the Weldon and Deacon processes generated enough chlorine for the production of about 150,000 tons per year of bleaching powder in England alone [6]. 

An important discovery during this period was the fact that steel is immune to attack by dry chlorine [7]. This permitted the first commercial production and distribution of dry liquid chlorine by Badische Anilin-und-Soda Fabrik (BASF) of Germany in 1888 [8,9]. This technology, using H2SO4 for drying followed by compression of the gas and condensation by cooling, is much the same as is currently practiced. 

In the latter part of the 19th century, the Solvay process for caustic soda began to replace the LeBlanc process. The resulting shortage of HCl made it necessary to find another route to chlorine. 

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Even though the involvement of graphite in the chlor-alkali industry is now history, this application remains important to this chapter, because it remains the largest and most reliable source of information about the mechanism of graphite corrosion and ways to limit the rate of corrosion [1 -3]. The graphite lost from the anode was found partly as sludge in the base of the cells, but CO and CO2 were also found to contaminate the chlorine off-gas. Evidently, graphite consumption results from anodic oxidation... 

An important sector of heavy inorganic chemical manufacturing is the production of chlorine and sodium hydroxide — the chlor-alkali industry. The manufacture of these chemicals has a long history. Today they are produced simultaneously by the electrolysis of sodium chloride solutions, but this was not always the case. The two chemicals were originally manufactured by different routes. In the 19th century chlorine was made by the oxidation of hydrogen chloride (itself made by reaction of salt with sulfuric acid) using the Deacon process. Sodium hydroxide was prepared by the reaction of calcium hydroxide with sodium carbonate — the lime-soda process. 

Electrochemical technology has a history dating back deep into the nineteenth century and carbon electrodes have been major players in this success [1-4]. In the early cells for both the two largest electrolytic industries, chlor-alkali and aluminum extraction, the electrodes were blocks of carbon or graphite. The past 50 years, however, has seen the development of carbons with different structures and often their availability in a range of forms. Thus, it is possible to purchase electrodes based on graphites, carbons, thermally treated carbons (e.g., vitreous or glassy carbon), expanded carbons, carbon/polymer composites, and doped diamond materials. Moreover, some of these materials are available in many forms as follows ... 

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