Study On Reaction Process For Synthesis Of Polycarbonate Precursors By Dimethyl Carbonate With Bisphenol A

Polycarbonate(PC)is one of the most widely used thermoplastics due to its excellent properties such as light transmission,impact resistance and thermal stability,and its consumption grows fastest among the five general engineering plastics.Conventional PC is synthesized from bisphenol A(BPA)and phosgene,which leads to serious environment pollution for the use of toxic raw material and organic solvent.Therefore,it is of great significance to develop a green non-phosgene PC synthesis process.Melt polymerization process of BPA and dimethyl carbonate(DMC)has been paid great attention,however,the preparation of high-molecular-weight polycarbonate via this method is still a tremendous challenge due to the low conversion of BPA and poor selectivity of carboxymethylation products.In this paper,synthesis of polycarbonate precursors with DMC and BPA catalyzed by metal acetylacetonates was studied,and the main contents and results were as follows:(1)Firstly,two series of metal acetylacetonates were used to catalyze the transesterification reaction of DMC and BPA.It was found that metal acetylacetonates based on transition metal exhibited better catalytic properties compared to the alkali and alkaline earth metals.Among these catalysts,zirconium acetylacetonate exhibited the best catalytic performance with the conversion of BPA and the selectivity of carboxymethylation products up to 85.2%and 99%at the optimum reaction condition,respectively.According to the FT-IR,¹H NMR and density functional theory calculation results,the reaction mechanism was proposed which revealed that the transesterification of DMC and BPA was activated by the metal-ligand synergistic effect.(2)In order to facilitate the separation of catalyst from the reaction system,we further prepared heterogeneous catalysts by grafting metal acetylacetonates onto SBA-15 molecular sieves and their catalytic properties were evaluated.Among them,La(acac)₃APTS@SBA-15 exhibited the best catalytic performance.Additionally,the effects of metal loading amount,catalyst usage,feed ratio,reaction temperature and reaction time on catalytic performance were investigated.After optimizing the reaction parameters,the conversion of BPA and the selectivity of carboxymethylation products up to 38.9%and 95.1%were achieved,respectively.