聚碳酸酯在亚临界水中解聚的研究

DEPOLYMERIZATION OF POLYCARBONATE IN SUB-CRITICAL WATER

采用间歇式高压反应装置研究聚碳酸酯(PC)在亚临界水中的解聚.在温度260～340℃、压力4.8～14.8 MPa、反应时间5～60 min的反应条件下,考察了反应温度及反应时间对PC解聚率及主产物双酚A(BPA)和苯酚(PhOH)回收率的影响.产物分别采用傅里叶红外光谱(FTIR)、扫描电子显微镜(SEM)、气质联谱(GC-MS)和气相色谱(GC)进行分析.实验结果表明,亚临界水能有效地降解PC,反应温度和反应时间是影响PC降解的主要因素.在反应温度300℃,反应压力8.7 MPa,反应时间45 min条件下,PC完全解聚,目标产物BPA收率36.88%,苯酚收率31.16%.在实验基础上,提出PC水解反应机理.通过实验数据关联,得出解聚反应级数为准一级,解聚反应活化能为125.7 kJ.mol-1.

The characteristics of depolymerization of polycarbonate （PC） in sub-critical water were investigated in the range of 260 ～340℃ and 5 -60 min by using a high-pressure batch autoclave reactor. It was found that PC could be effectively depolymerized in sub-critical water. The main products were bisphenol A （BPA） and phenol,which were analyzed by FTIR, SEM, GC/MS and GC. It was found that the temperature and reaction time were important factors in the process of depolymerizaition. Swelling process of PC played an important role in this hydrolysis reaction, which occured in the region 280 - 300℃ accompanied by the remarkable hydrolysis. With the raising of the temperature and the reaction time,the yield of bisphenol A was increased at first and then reduced. Bisphenol A was unstable in the sub-critical water, it would further decompose into phenol, p-tert-butylphenol, p-isopropenylphenol etc. The result showed that at reaction temperature 300℃, reaction pressure 8.7 MPa and reaction time 45 min, the PC could be depolymerized completely with the yield of BPA and phenol were 36.88 % and 31. 16% , respectively. Based on the qualitative and quantitative analyses of the products,the reaction mechanism,i, e. random scission and hydrolytic reaction occurred simultaneously during the process of depolymerizaition of PC was proposed. The results of kinetic analysis indicated that the depolymerization followed a pseudo-first-order kinetics and the activation energy of PC depolymerizaition in sub-critical water obtained from Arrhenius equation was 125.7 kJ·mol^-1.