Phenol → Diphenyl carbonate

Participants

Reaction Conditions

Reaction Steps

In a vertical, cooled tube reactor, a mixture of 145.2 kg/h of 14.5% strength sodium hydroxide solution, produced by diluting 65.8 kg/h of a 32.0% strength sodium hydroxide solution with 79.4 kg/h of deionized water (DI water), and 48.3 kg/h of phenol was continuously combined with a solution of 86.2 kg/h of methylene chloride and 27.5 kg/h of phosgene (8 mol % excess based on phenol). This reaction mixture was cooled to a temperature of 33° C. and after an average residence time of 15 seconds, a pH of 11.5 was measured. In the second stage of the process, 5.4 kg/h of 50.0% strength NaOH were then metered into this reaction mixture so that the pH of the second reaction stage after a further residence time of 5 minutes is 8.5. In the second stage of the process, the reaction mixture was mixed continually by passage through a tube provided with constrictions, The reaction temperature was, after renewed addition of the NaOH, set to 30° C. by cooling. After the organic phase had been separated off from the aqueous phase (reaction wastewater), the DPC solution was washed with 0.6% strength hydrochloric acid and water. Removal of the solvent gave 99.9% strength diphenyl carbonate. The reaction wastewater was not combined with the washing phases and was freed of solvent residues and catalysts by stripping with steam. After neutralization (pH 7) with hydrochloric acid and treatment with activated carbon, the reaction wastewater contained 17.0% of NaCl and <2 ppm of phenol.

Provenance & Evidence