Patent ID: 7145029

Claim:
A process for producing polycarbonate which comprises the following steps: (a) reacting an alkylene with an oxygen-containing gas, thereby producing an alkylene oxide, carbon dioxide, and water; (b) reacting at least a portion of said alkylene oxide with said carbon dioxide in the presence of a carbonation catalyst comprising [1,1′(1-butylbenzimidazol-2yl)pentane]copper(II) di(trifluoromethanesulfonate) at a temperature in the range of about 50° C. to 250° C. and at a pressure of at least about 1379 kPa (200 psig) to provide a crude cyclic carbonate stream comprising a cyclic carbonate and said carbonation catalyst; (c) reacting said cyclic carbonate and said carbonation catalyst with an aliphatic monohydric alcohol in the presence of a transesterification catalyst to provide a crude product stream comprising dialkyl carbonate and diol, wherein said crude product stream has a halogen concentration of about 5 ppm or less; (d) separating said dialkyl carbonate from said diol, thereby producing a dialkyl carbonate-enriched stream; (e) reacting said dialkyl carbonate-enriched stream and phenol in the presence of a metal-containing catalyst at a temperature in the range between about 80° C. to 300° C. and at a pressure in the range between about 2 kPa to 4000 kPa (absolute pressure), thereby producing diphenyl carbonate and alkanol; (f) separating said diphenyl carbonate from said alkanol, thereby producing a diphenyl carbonate-enriched stream; (g) reacting said diphenyl carbonate-enriched stream with bisphenol-A, thereby producing polycarbonate and phenol; and (h) separating said polycarbonate from said phenol, thereby producing a polycarbonate-enriched stream.