Question

what is alkali process?​

Answer 1

Answer:

The chloralkali process (also chlor-alkali and chlor alkali) is an industrial process for the electrolysis of sodium chloride solutions. It is the technology used to produce chlorine and sodium hydroxide (lye/caustic soda),[1] which are commodity chemicals required by industry. 35 million tons of chlorine were prepared by this process in 1987.[2] Industrial scale production began in 1892.

Old drawing of a chloralkali process plant (Edgewood, Maryland)

Usually the process is conducted on a brine (an aqueous solution of NaCl), in which case NaOH, hydrogen, and chlorine result. When using calcium chloride or potassium chloride, the products contain calcium or potassium instead of sodium. Related processes are known that use molten NaCl to give chlorine and sodium metal or condensed hydrogen chloride to give hydrogen and chlorine.

The process has a high energy consumption, for example around 2500 kWh of electricity per tonne of sodium hydroxide produced. Because the process yields equivalent amounts of chlorine and sodium hydroxide (two moles of sodium hydroxide per mole of chlorine), it is necessary to find a use for these products in the same proportion. For every mole of chlorine produced, one mole of hydrogen is produced. Much of this hydrogen is used to produce hydrochloric acid, ammonia, hydrogen peroxide, or is burned for power and/or steam production.[3]

Answer 2

The raw material for producing sodium hydroxide is sodium chloride (common salt). Sodium hydroxide is produced by the electrolysis of a concentrated aqueous solution of sodium chloride (called Brine).

When electricity is passed through a concentrated solution of sodium chloride, it decomposes to form sodium hydroxide, chlorine and hydrogen :

$\displaystyle\sf 2NaCl\:(aq) + 2H_2O\:(l) \underset{(Electrolysis)}{\xrightarrow{Electricity}} 2NaOH\;(aq)+Cl_2\:(g)+H_2\:(g)$

During Electrolysis, chlorine gas is produced at the anode (positive electrode) and hydrogen gas is produced at the cathode (negative electrode). Sodium hydroxide solution is formed near the cathode. All the products of electrolysis of sodium chloride solution, chlorine, hydrogen and sodium hydroxide, are collected and stored seperately.

The process of electrolysis of sodium chloride solution is called chlori-alkali process because of the products formed chlor for chlorine and alkali for sodium hydroxide.