Phenol Production by Benzene Sulfonation Process

Benzene sulfonation process flow diagram for phenol production

Phenol production process flowsheet by benzene sulfonation

Phenol Production  brief process description by the Benzene Sulfonation Process technology:

Benzene can be converted to phenol with the help of inorganic acids and salts and this process is oldest of all the process where phenol is produced by reactants such as cumene and toluene.

This process involves four major chemical reactions which are:

Sulfonation: Benzene is reacted with sulphuric acid to form benzene sulphonic acid at 150 to 170 deg centigrade

Neutralization: Benzene sulphonic acid is reacted with sodium sulfite to form sodium benzene sulphonate

Fusion: Sodium benzene sulphonate is fused with sodium hydroxide to form sodium phenoxide

Acidification: sulphuric acid and sodium phenoxide are reacted to produce crude phenol and sodium sulphite.

The above reaction step explains the requirement of the unit operation equipment in the process as
  • Filtration: Pressure filter and centrifuge used in the separation of sodium sulphate and sodium sulphite
  • Distillation: Separation of phenol from crude phenol
  • Crystallization: Separation and recovery of sodium sulphite

Process description: This process is large-scale batch cycle operation due to slow reaction step at fusionator. Sodium benzene sulphonate is fed to cast iron make fusion pots which already contains molten caustic soda at a temperature of 300 deg centigrade, due to slow reaction with take about 5-6 hours of residence time the pot is fed at regular intervals where continuous loading and unloading of the pot occurs for continuity of the process, thus sodium phenoxide fraction which is obtained is fed to acidifier to produce crude phenol by reacting with sulphuric acid and sulphur dioxide. Vacuum distillation column is used to get phenol from crude phenol and remain salts are stripped in a steam stripper to remove phenol from them and aqueous salts. Crystallizers are used to increase the purity of the sodium sulphite; these crystals are separated from mother slurry by a continuous centrifugal separator, which is recycled to neutralizer.