Method and apparatus for waste stream recovery

1. A method for manufacturing a polycarbonate comprising melt reacting a diaryl carbonate and a bisphenol in presence of one or more transesterification catalysts, wherein said diaryl carbonate is manufactured by a diaryl carbonate manufacturing process utilizing a feed comprising a product mixture recovered from waste streams from said diaryl carbonate manufacturing process and further wherein said product mixture comprises a dialkyl carbonate, an aromatic alcohol and an alkyl alcohol; and said waste stream comprises said transesterification catalyst, said diaryl carbonate, an aromatic salicylate and polycarbonate oligomers.

2. A method for manufacturing a polycarbonate comprising (i) recovering a product mixture from a diaryl carbonate manufacturing waste stream by: (a) reacting a waste stream with an alkyl alcohol to form a reaction mixture comprising said product mixture and at least one waste component; (b) separating said product mixture from said reaction mixture, (ii) manufacturing diaryl carbonate from the product mixture, and (iii) melt reacting the diaryl carbonate and a bisphenol in the presence of one or more transesterification catalysts to form the polycarbonate.

3. The method for manufacturing polycarbonate according to claim 2 , wherein diaryl carbonate not manufactured from the product mixture is also reacted with the bisphenol.

4. A method for manufacturing a polycarbonate comprising reacting a diaryl carbonate and a bisphenol in the presence of one or more transesterification catalysts, wherein the diaryl carbonate is manufactured from a product mixture and the product mixture is recovered from a diaryl carbonate manufacturing waste stream by a method comprising:

reacting said waste stream with an alkyl alcohol to form a reaction mixture comprising said product mixture and at least one waste component; and

separating said product mixture from said reaction mixture.

5. A method for manufacturing a polycarbonate comprising reacting a diaryl carbonate and a bisphenol in the presence of one or more transesterification catalysts, wherein the diaryl carbonate is manufactured from a product mixture and the product mixture is recovered from a diaryl carbonate manufacturing waste stream by a method comprising:

introducing reactant streams comprising a dialkyl carbonate, an aromatic alcohol and a transesterification catalyst to a first reactive distillation column;

recovering from said first reactive distillation column a first top stream comprising said dialkyl carbonate, an alkyl alcohol, an alkyl aryl ether and said aromatic alcohol and a first bottom stream comprising an alkyl aryl carbonate, said transesterification catalyst, diaryl carbonate and an aromatic salicylate;

introducing said first bottom stream into a second reactive distillation column to produce a diaryl carbonate;

recovering from said second reactive distillation column a first side stream comprising said dialkyl carbonate, aromatic alcohol, alkyl aryl ether and a second bottom stream comprising said diaryl carbonate, alkyl aryl carbonate, transesterification catalyst, aromatic salicylate and dialkyl carbonate;

introducing said first side stream into a second rectification column to separate a dialkyl carbonate stream from said alkyl aryl ether and said aromatic alcohol, and recycling said dialkyl carbonate stream to a first rectification column;

introducing said second bottom stream to a third reactive distillation column;

recovering from said third reactive distillation column a second top stream comprising unreacted said aromatic alcohol, dialkyl carbonate and alkyl aryl ether and recycling said second top stream to said first reactive distillation column;

introducing said first top stream into said first rectification column;

recovering from said first rectification column a first azeotrope top stream comprising said dialkyl carbonate/alkyl alcohol azeotrope, and a third bottom stream comprising said dialkyl carbonate, aromatic alcohol and alkyl aryl ether and recycling said third bottom stream to said first reactive distillation column;

recovering a fourth bottom stream comprising said diaryl carbonate from the bottom of said third reactive distillation column and introducing said fourth bottom stream into a first evaporator;

recovering from said first evaporator a third top stream comprising said diaryl carbonate, alkyl aryl carbonate, aromatic alcohol, an alkyl salicylate and an aromatic salicylate and a fifth bottom stream comprising said diaryl carbonate, aromatic salicylate and transesterification catalyst and introducing said fifth bottom stream into a second evaporator;

recovering from said second evaporator a fourth top stream comprising said diaryl carbonate and a sixth bottom stream comprising said transesterification catalyst, said diaryl carbonate and said aromatic salicylate;

splitting said sixth bottom stream into a first recycle stream and a first bottom waste stream and recycling said first recycle stream into said first reactive distillation column;

introducing said third top stream and said fourth top stream into a third rectification column;

recovering from said third rectification column a fifth top stream comprising said alkyl aryl carbonate and aromatic alcohol and a seventh bottom stream comprising said diaryl carbonate, polycarbonate oligomers, said aromatic salicylate and said transesterification catalyst;

introducing said fifth top stream to said third reactive distillation column and introducing said seventh bottom stream into a fourth rectification column;

recovering from said fourth rectification column a sixth top stream comprising said diaryl carbonate and a second bottom waste stream comprising said diaryl carbonate, polycarbonate oligomers, aromatic salicylate and transesterification catalyst;

introducing said second bottom waste stream, said first bottom waste stream and said alkyl alcohol into a mixing unit to produce said waste stream;

introducing said waste stream into one or more reactors;

reacting said waste stream with said alkyl alcohol to form a reaction mixture;

introducing said reaction mixture into a separating unit;

recovering from said separation unit said product mixture and an eighth bottom stream comprising a bisphenol, said transesterification catalyst and unreacted waste;

introducing said eighth bottom stream into a disposal unit, wherein said product mixture comprises a dialkyl carbonate, an aromatic alcohol and said alkyl alcohol; said waste stream comprises a transesterification catalyst, said diaryl carbonate, an aromatic salicylate and polycarbonate oligomers; and said reaction mixture comprises said dialkyl carbonate, said aromatic alcohol, said alkyl alcohol, a bisphenol, an alkyl salicylate, and unreacted waste.