ChloralkaliVerfahren

The chloralkali process is an industrial process for the production of sodium hydroxide (NaOH) and chlorine (Cl2) from brine (sodium chloride, NaCl, in water). It is one of the most important chemical processes in the chemical industry, with a global production capacity of over 60 million metric tons of chlorine per year. The process is based on the electrolysis of sodium chloride dissolved in water, which occurs in an electrolytic cell.

The electrolytic cell consists of a cathode and an anode, both made of a suitable material such as titanium or stainless steel. The cathode is typically made of a metal that is easily oxidized, such as mercury or lead, while the anode is made of a material that is resistant to corrosion, such as graphite or platinum. The electrolytic cell is filled with a solution of sodium chloride, which is heated to a temperature of around 90°C to increase the conductivity of the solution.

When an electric current is passed through the electrolytic cell, the sodium chloride dissociates into sodium (Na+) and chloride (Cl-) ions. The sodium ions migrate to the cathode, where they are reduced to sodium metal, which is then reacted with water to produce sodium hydroxide and hydrogen gas. The chloride ions migrate to the anode, where they are oxidized to chlorine gas. The chlorine gas is then collected and purified for use in various industrial applications.

The chloralkali process is an energy-intensive process, with an energy consumption of around 3-4 kWh per kilogram of chlorine produced. However, it is a highly efficient process, with a yield of over 90% for both sodium hydroxide and chlorine. The process is also environmentally friendly, as it produces no greenhouse gases or other pollutants. However, the process does produce hydrogen gas, which can be a safety hazard if not properly managed.

The chloralkali process has been in use since the early 20th century and has undergone several improvements and modifications over the years. Today, it is a well-established and widely used process for the production of sodium hydroxide and chlorine, with applications in a wide range of industries, including the chemical, pharmaceutical, and food industries.