Production of Phenol from Chlorobenzene route
Reactions for Production of Phenol
There are three reactions to convert benzene to phenol using chlorination route
Chlorination
• Benzene + Cl2 → monochloro benzene
• Operating temperature: 85°C
• Catalyst: Fe or FeCl3 catalyst
Causticization
• Benzyl chloride + NaOH → sodium benzoate
• NaOH is in aqueous media
• Operating conditions: 425°C and 350 atms
• Exothermic reaction
Hydrolysis
• Sodium benzoate + HCl (aq) → Phenol + NaCl (aq)
• Operating conditions: Nothing specific
Production of Phenol Process Flow Diagram
Figure. Flow sheet of Production of phenol from chlorobenzene route
• Benzene is first dried. Dry benzene and FeCl3 catalyst enters the chlorination reactor.
• After the solid-gas-liquid reaction, the products are further heated up to enter a fractionator.
• The fractionator separates benzene as a top product and monochloro benzene as the bottom product. The top product also consists of HCl off gas that is obtained as the vapour stream from the partial condenser.
• The benzene is further cooled and sent back to the reactor and also as a reflux to the fractionator.
• The bottom product monochloro benzene is mixed with 10% NaOH solution and diphenyl oxide to enter a high pressure pump followed with heat integrated heat exchanger that pre-heats the feed to higher temperature.
• The feed then enters the causticization reactor which has cooling water tubes to control the temperature.
• The product stream is cooled using heat integrated exchanger and then enters a neutralizer that is fed with the HCl obtained from the fractionator partial condenser.
• After neutralization, the product phenol is separated from the aqueous phase using gravity settling principle.
• The organic layer rich in phenol is sent to a vacuum column to separate the phenol from diphenyl oxide (bottom product). The bottom product is partially recycled to enter the cauticization reactor.