SYNTHESIS OF POLYCARBONATE MONOMERS BY CO_2 INSERTION IN EPOXIDES OVER ZEOLITE-BASED CATALYSTS

摘要

A novel application of molecular sieves in the synthesis of cyclic carbonate monomers of polycarbonates is reported. Titanosilicate molecular sieves (TS-1 and TiMCM-41) and zeolite-Y-encapsulated metal phthalocyanines (MPc-Y; M = Al, Cu, Co and Ni) are highly active in the coupling reaction of CO_2 with epoxides, like epichlorohydrin, propylene oxide and styrene oxide, to yield cyclic carbonates at low temperatures and pressures. The cyclic carbonates can also be prepared from the olefins in the same reactor by reacting the olefins with a mixture of an epoxidizing agent (like H_2O_2, tert-butyl hydroperoxide and dioxygen) and CO_2 over titanosilicate molecular sieves or zeolite-Y-encapsulated metal phthalocyanines. A novel transesterification of the cyclic carbonates with methanol and phenol over TiMCM-41 yielded the corresponding dimethyl and diphenyl carbonate monomers, thereby opening a "clean technology" route for polycarbonates avoiding currently used toxic and hazardous chemicals, like phosgene or carbon monoxide.