The history of the development of electrochemical methods for the production of chlorine and sodium hydroxide. Part 1

The state of chemical methods of chlorine production

The history of the development of electrochemical methods for the production of chlorine and sodium hydroxide. Part 1 With the development of industry, the demand for chlorine, which is used to produce various chlorine-containing compounds, has continuously increased. The main way of obtaining chlorine for many years was based on the interaction of hydrochloric acid with manganese dioxide (pyrolusite). In this way chlorine was first obtained in 1774 by the Swedish chemist KV Scheele. However, this method was very expensive due to a deficiency of hydrochloric acid and pyrolusite.

The situation changed dramatically in the 60s of the XIX century. As a result of technological solutions for the utilization of hydrogen chloride in the leblon soda process and its effective conversion to chlorine. In the face of the enormous scale of the Leblanov soda production, large amounts of hydrogen chloride released into the atmosphere began to poison the environment and cause protests from the population. Some factories even had to be shut down and transferred to areas remote from populated areas. This problem was especially acute in England. It is no coincidence that it was in this country that a special law ("Alkali Act") was issued in 1863, banning the release of gases containing more than 5% of hydrogen chloride to the atmosphere. This governmental decision placed the manufacturers in a very difficult position, but at the same time pushed them to find effective technical methods for capturing and using hydrogen chloride.

Already in 1866 the English chemist Weldon took a patent for the method of processing hydrogen chloride for chlorine for the purpose of using it for the production of bleached lime.

V. Veldon proposed the production of chlorine, using the already known chemical reaction of the interaction of hydrochloric acid and manganese dioxide. However, the scheme introduced an innovation that allowed the regeneration of manganese dioxide from manganese chloride formed in the process of interaction with hydrochloric acid. According to available data, the expenses for the regeneration of dioxide-manganese did not exceed 1871, 25% of the cost of an equal amount of natural pyrolusite.

The second method was proposed by G. Deacon, who patented it in England in 1868. The method consisted in obtaining chlorine by the contact oxidation of hydrogen chloride with air oxygen. The catalyst was sulfuric acid copper, deposited on broken brick. G.Dikon's method provided a somewhat greater yield of chlorine than V. Veldon's method, but, nevertheless, he could not displace it. This is due to the simpler design of the apparatus in the Veldon process and the higher concentration of the produced chlorine. Thus, according to the method of Weldon, chlorine concentrations were up to 95%, while according to the method of Deacon the chlorine concentration did not exceed 14%.

Both methods marked the beginning of the largest branch of the chemical industry - the production of chlorine and chlorine products. Inextricably linked with the lebanon soda process, they "extended the century" of the Leblanov production and contributed to the development of the soda industry.

The monopolistic position of the Weldon and Deacon method in chlorine production continued until the appearance of the nineteenth century in the 1990s. A new electrochemical method for the production of chlorine from alkali metal chlorides (potassium and sodium). These methods were used in a number of countries and in the first years of this century. So, according to the method of Weldon, there were 7 factories in England, Germany, France, Belgium and Russia. The way of the Deacon was used at this time at 6 plants, including: in Germany - on two, in France - on two, in Belgium - at one plant.

It is interesting to note that in 1903, at the large chemical plant in Aussiga (Austria), where the production of electrolytic chlorine existed, the Weldon process was simultaneously used.

In Russia, chlorine was produced according to the method of Weldon. The first plant that introduced this process in 1888 was Ushkov's chemical plant, built in 1868. In addition, the Konstantinovsky plant also worked in the way of Weldon (since 1910), but in 1917 production was suspended. At the end of XIX century. A new electrochemical process has come to replace the chemical methods of obtaining chlorine, which in the beginning of the twentieth century conquered it. The dominant position in the world's chlorine industry.

Development of electrochemical process of chlorine production

The appearance of an electrochemical process for the production of chlorine is inextricably linked with the general progress of science and technology in the second half of the nineteenth century: the achievements of chemistry and physics, the development of the theory of electrolytic dissociation, and the successes of electrical engineering.

The first known proposal to produce electrolytic sodium hydroxide and chlorine belongs to the Russian scientists NG Glukhov and F. Vashchuk, who patented on December 2, 1879 in Germany, "a method for obtaining caustic alkali by electrochemical means". The apparatus proposed by them represented an electrolyzer, "separated by a septum." The anode was made of platinum or graphite, and the cathode was made of iron. The inventors noted that their method could be used not only for decomposition of table salt, but also for sodium sulfate.

In 1884 the German engineer K. Hepfner took a patent for "improvement in the electrolysis of halide salts of light and heavy metals," which attracted the attention of chemical technologists.

By the eighties of the XIX century. The first factory experiments of electrochemical production of chlorine at the plant "Griesheim-Elektron" (Germany). When decomposing aqueous solutions of alkali metal chlorides (potassium or sodium) with direct current under certain conditions, three products were simultaneously obtained: chlorine, hydrogen and sodium hydroxide (or caustic potash). In the process of electrolysis, gaseous chlorine is released at the anode, and on the cathode a metallic soda, which, reacting with water, releases hydrogen and forms an alkali metal hydroxide. Of the three named products, a special (commercial) interest represented caustic soda at the time. Thus, the production of chlorine proved to be associated with the production of the most important alkalis. Since that time, scientists, engineers and entrepreneurs have begun to show increased interest in the chlorine electrochemical process.

In the short term, several technological schemes have been created, which, depending on the electrolysers used, can be divided into three main groups:

1) with a solid cathode and a porous diaphragm,

2) with mercury cathode

3) with a bell.

The history of the development of electrochemical methods for the production of chlorine and sodium hydroxide

The first, the earliest technological scheme was based on the use of electrolyzers with a solid cathode and a porous diaphragm. The purpose of the diaphragm is to separate the anode and cathode spaces in order to protect the chlorine and caustic soda from the electrolyte from chemical interaction. The solution of sodium hydroxide formed as a result of the electrolyte is then evaporated and dehydrated. It turns out a technical product - caustic soda with a content of about 90-95% sodium hydroxide.

Successfully begun in the 80s at the plant in Griesheim, experimental work on the practical introduction of the process of electrochemical production of chlorine in a plant with a solid cathode and a diaphragm resulted in the launch in 1890 of the first small electrolytic plant in the same city. The plant was equipped with an electrolytic plant with a capacity of 200 liters. from. And produced sodium hydroxide and chlorine. In 1892, the plant's capacity doubled. The enterprise worked successfully, so the electrochemical method of producing chlorine and caustic soda continued to spread rapidly. In 1894, a large factory in Bitterfeld (Germany) was commissioned. In 1895, the production of this enterprise doubled.

At the same time, the expansion of the plant in Griesheim began, which was completed in 1896. In addition, the second plant with a capacity of 2000 hp belonging to the company Elektrochemische Werke Bitterfeld, equipped with clay baths with asbestos diaphragms, was launched in Bitterfeld.

The method of obtaining chlorine and sodium hydroxide in electrolyzers with a solid cathode and diaphragm has become widespread in the factories of the company "Griesheim-Elektron". In 1903, 11 factories of this society produced most of all alkalis and whitewash produced by all electrolytic plants in Germany. The company owned two factories in Griesheim, two large plants in Bitterfeld and one in the Rhine-Velden.

The method with a solid cathode and diaphragm was also used at the German plants of the Consolidierte Alkaliwerke company in Vesterageln and at the Badische Anilin a Sodafabrik Baden aniline and soda factory.

In addition, this method was adopted in France at the Compagnie industrielle de produits chimiques, which produced 2000 tons of caustic soda and about the same amount of bleached lime, and also in Spain at the plant in Flicks near Barcelona.

The history of the development of electrochemical methods for the production of chlorine and sodium hydroxide

In Russia, the electrochemical method with a solid cathode and a diaphragm (the "Griesheim-Electron" system) began to be applied at the plant of the joint-stock company "Electricity" in 1895-1896. And at the plant of the South Russian Society for the production and sale of soda in the city of Slavyansk. At the Slavic plant, 120 electrolysers were used to produce electrolytic chlorine and sodium hydroxide, which made it possible to produce 3,280 tons of caustic soda and about 2,730 tons of chlorine (or 8,200 tons of bleach per year). During the First World War, the Slavic plant was expanded: the number of electrolysers was increased from 120 to 210.

During the First World War in the Donbass at the station Rubezhnaya was built (1916) chemical plant "Russkokraska" with an electrolytic shop equipped with 200 electrolyzers of the system "Griesgeym Electron." The plant produced 5,300 tons of sodium hydroxide and 12,000 tons of bleach.

Shukhardin S. "Technology in its historical development"