Phenol → Diphenyl carbonate

Participants

Reaction Conditions

Reaction Steps

In a vertically upright cooled tubular 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% strength sodium hydroxide solution with 79.4 kg/h of demineralized 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 a median residence time of 15 seconds, a pH of 11.5 was measured. Then, in the second stage of the process, to this reaction mixture was added 5.4 kg/h of 50% strength NaOH, so that the pH of the second reaction stage, after a further residence time of 5 minutes, was 8.5. In the continuously operated reaction, metering fluctuations which occurred were contained by respective adaptations of the NaOH feeds. In the second stage of the process, the reaction mixture was constantly mixed by passing it through a tube provided with constrictions. The reaction temperature, after repeated addition of NaOH, was set to 30° C. by cooling. After separating off the organic phase from the aqueous phase (reaction wastewater), the DPC solution was washed with 0.6% strength hydrochloric acid and water. After removal of the solvent, 99.9% pure diphenyl carbonate was obtained. The reaction wastewater was combined with the wash phases and freed from solvent residues and catalyst by stripping with steam. After neutralization with hydrochloric acid and treatment with activated carbon, the reaction wastewater contained 17% by weight NaCl and less than 2 ppm of phenol.

Provenance & Evidence