Cholorobenzene and Caustic Process for Phenol Production

Process flow sheet for Phenol Production from Chlorobenzene and Caustic Process
Phenol by Chlorobenzene-NaOH

Process Description of Chlorobenzene and Caustic process for phenol production:

For 1 ton of phenol production approximately the following raw materials are required as per the process described:
Benzene =        0.90 tons
Chlorine =        0.82 tons
NaOH   =         0.67 tons
HCl       =          0.51 tons
 The main reactions which take place for this process are:
1. Chlorination
    C6H6 + Cl2 ---> 85oC , Fe- --> C6H5Cl (Chlorobenzene)
2. Causticization
    C6H5Cl +NaOH (aq)---> C6H5NaO
3. Hydrolysis
    C6H5NaO + HCl(aq) ---- > C6H5OH + NaCl(aq)

A Short Process Description for Phenol Production:

Benzene which is in dry state, reacted with chlorine at the presence of  the catalyst iron or anhydrous ferric chloride at about 85 deg centigrade temperature to form Chlorobenzene in a chlorination tower, unconverted benzene is recycled and monochlorobenzene is withdrawn all excess chlorine is used in neutralizer and about 10% solution of dilute caustic soda is mixed with Chlorobenzene which is reacted with caustic solution where chlorine present at the benzene ring is reacted with hydrogen and produce water vapors which are removed a tail gas. The resulting product diphenly oxide is pumped to the preheater and then passed to multi-tube reactor where causticization reaction occurs at the parameters 425 deg centigrade and 350 atm pressure, then the reacted mixture is passed to the neutralizer through the effluent heat exchangers.
Phenol is obtained from hydrolysis occurs at the neutralizer where reaction with concentrated hydrochloric acid take place to form phenol and sodium chloride.

Sodium chloride is formed as a side product, this salt is separated and send to electrolysis.
Upstream from the separator is sent to vacuum distillation column where phenol is stripped out. About 95% yield is obtained and diphenyl oxide is removed from the bottom of the column to recycle.

Major engineering problems in this process are:

HCl corrosion in Chlorobenzene plant section
High-pressure vessel design for causticization reactor
Phenol production by Benzene Sulfonation process
cumene peroxide process for phenol production