Process for preparing diaryl carbonates and polycarbonates
AssigneeBayer MaterialScience AG
InventorsPieter Ooms, Andreas Bulan
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Abstract
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 thermal 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).
Claims18
A process for preparing diaryl carbonate, which comprises the steps of:
- (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 homogeneous metal catalyst to form at least one diaryl carbonate and hydrogen chloride;
- (c) isolating and working-up the diaryl carbonate formed in step (b);
- (d) isolating and optionally purifying the hydrogen chloride formed in step (b);
- (e) thermally oxidizing at least part of the hydrogen chloride from step (d) to chlorine by oxygen forming a gas mixture with formation of water;
- and
- (f) recirculating at least part of the chlorine prepared in step (e) to the preparation of phosgene in step (a);
- wherein the thermal oxidation by oxygen in step (e) is carried out using one or more catalyst, and wherein the catalyst is selected from the group consisting of titanium chloride, zirconium chloride, aluminum chloride and titanium phenoxide.
Dependencies are inferred from the claim text.