Study On Alcoholysis Of Waste Polycarbonate To Recover Bisphenol A And Dialkyl Carbonate

1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]) was synthesized using1-chlorobutane and N-methylimidazole as starting materials. The reaction conditions were optimized by single factor experiments and orthogonal test. The obtained optimum reaction conditions were temperature100℃, agitation rate6r/s, n(1-chlorobutane):n(N-methylimidazole)=1.1:1and reaction time12h. Under above conditions, the yield of product was over96%. It was found that second-order rate law could be utilized to characterize the reaction with activation energy of138KJ/mol. The structure of the product was characterized by FT-IR and NMR.The methanolysis of waste CD was investigated using ionic liquid [Bmim][Cl] as reaction medium and catalyst. The effects of reaction temperature, methanol dosage,[Bmim][Cl] dosage and reaction time on the methanolysis reaction were examined. It was shown that the conversion of waste CD was over99%, the yield of bisphenol A (BPA) and dimethyl carbonate (DMC) was over95%and91%under the optimum conditions of reaction temperature115℃, n(methanol):n(waste CD)=6:1, m([Bmim][Cl]):m(waste CD)=12and reaction time2.0h. The structure of obtained products was characterized by GC, FT-IR and HPLC. The ionic liquid could be reused up to10times without apparent decrease in the conversion of waste CD, yield of BPA and DMC.The ethanolysis of waste CD was investigated using ionic liquid [Bmim][Cl] as reaction medium and catalyst. The effects of reaction temperature, ethanol dosage,[Bmim][Cl] dosage and reaction time on the ethanolysis reaction were studied. Under the optimum conditions of reaction temperature130℃, n(ethanol):n(waste CD)=6:1, m([Bmim][Cl]):m(waste CD)=1:2and reaction time2.0h, the conversion of waste CD was99%, the yields of BPA and diethyl carbonate (DEC) were over95%and91%respectively. The structure ofobtained products was characterized by GC, FT-IR and HPLC. The ionic liquid could be reused up to10times without apparent decrease in the conversion of waste CD, yield of BPA and DEC.The obtained optimum purification conditions for coarse product BPA were studied. The effects of the dosage and variety of activated carbon, temperature and time were examined. Under the optimum conditions of4%dosage of active carbon, time20min and temperature20℃, the discoloration rate was83%. The obtained optimum recrystallization solvent was toluene, the dosage of solvent was5.0g/g, and recrystallization temperature was room temperature. Under above optimum conditions, the yield was over88%and the purity of BPA changed from98.5%to100%. Separation of dimethyl carbonate from methanol-dimethyl carbonate azeotrope was investigated, the yield and purity obtained product was over70%and99.5%. Diethyl carbonate was separated and purified; the purity obtained product was over99.5%.A novel method for alcoholysis of waste polycarbonate to recover BPA and dialkyl carbonate was developed by this study.