Process for producing polycarbonate
First Claim
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1. A process for producing polycarbonate comprising:
- a) producing phosgene by reacting chlorine with carbon monoxide;
b) reacting the phosgene formed in step a) with at least one bisphenol in the presence of an aqueous alkali metal containing base to form a polycarbonate and an alkali metal chloride-containing reaction waste water solution;
c) separating off and working up the polycarbonate formed in step b) from the alkali metal chloride-containing reaction waste water solution;
e) distilling at least a portion of the alkali metal chloride-containing reaction waste water solution remaining after step c) via osmotic membrane distillation to obtain an enriched alkali metal chloride-containing solution;
f) electrochemically oxidating of at least a portion of the alkali metal chloride-containing solution from e) to obtain chlorine, an alkali metal hydroxide solution and, optionally, hydrogen.
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Abstract
A process is described for producing polycarbonate and utilizing at least some of the process waste water by concentrating the sodium chloride-containing waste water phases for the electrolysis using osmotic membrane distillation, if appropriate with simultaneous dilution of the sodium hydroxide solution obtained from the electrolysis for the polycarbonate production process.
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Citations
20 Claims
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1. A process for producing polycarbonate comprising:
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a) producing phosgene by reacting chlorine with carbon monoxide; b) reacting the phosgene formed in step a) with at least one bisphenol in the presence of an aqueous alkali metal containing base to form a polycarbonate and an alkali metal chloride-containing reaction waste water solution; c) separating off and working up the polycarbonate formed in step b) from the alkali metal chloride-containing reaction waste water solution; e) distilling at least a portion of the alkali metal chloride-containing reaction waste water solution remaining after step c) via osmotic membrane distillation to obtain an enriched alkali metal chloride-containing solution; f) electrochemically oxidating of at least a portion of the alkali metal chloride-containing solution from e) to obtain chlorine, an alkali metal hydroxide solution and, optionally, hydrogen. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification