Process for preparing diaryl carbonates and polycarbonates

摘要

The present invention relates to a process for the continuous preparation of diaryl carbonates from phosgene and at least one monohydroxy compound (monophenol) in the presence of catalysts, and also the use thereof for preparing polycarbonates. The hydrogen chloride formed in the reaction is converted by electrochemical oxidation into chlorine, with the chlorine being recirculated to the preparation of phosgene. In particular, the process comprises utilization of the hydrogen chloride formed for the process for preparing diphenyl carbonate (DPC process).

主权项

1. A process for preparing diaryl carbonate, comprising:
(a) preparing phosgene by reaction of chlorine with carbon monoxide, (b) reacting the phosgene formed in step (a) with at least one monophenol in the presence of a catalyst to form at least one diaryl carbonate and hydrogen chloride, wherein the catalyst is selected from the group consisting of titanium chloride, zirconium chloride, aluminium chloride, and titanium phenoxide, (c) isolating and working-up of the diaryl carbonate formed in step (b), (d) isolating the hydrogen chloride formed in step (b), (e) preparing an aqueous solution of the hydrogen chloride, (f) electrochemically oxidizing at least part of the aqueous hydrogen chloride solution from (e) to chlorine with formation of water by using a gas diffusion electrode as an oxygen-depolarized cathode, and (g) recirculating at least part of the chlorine prepared in step (f) to the preparation of phosgene in step (a).