Stability Of Pc Depolymerization Products In Super/Sub-Critical Methanol And Methanol/Water Co-Solvent System

Stability of dimethyl carbonate (DMC) and bisphenol A (BPA), which are the products of polycarbonate (PC) depolymerization in super/sub-critical methanol, were studied in super/sub-critical methanol and water/methanol co-solvent system in a batch autoclave under different conditions. The experimental products were analyzed qualitatively and quantitatively by GC-MS, GC, LC-MS, HPLC and FT-IR. The research can provide foundation data for the PC depolymerization in super/sub-critical fliulds.The results showed that in super/sub-critical methanol system, stability of DMC was infected by temperature obviously. The recovery of DMC was only 80.4% after reaction time 10 minutes at temperature 320℃. On the other hand, stability of DMC was not influenced by pressure visibly. The products of DMC thermal decomposition were dimethyl ether and carbon dioxide. The result of kinetic analysis showed that the thermal decomposition reaction was first order and the activation energy was 39.7kJ·mol^-1.In super/sub-critical methanol system, stability of BPA was researched. The results reflected that in the research conditions, stability of BPA influenced by temperature obviously while slightly by pressure. The recovery of BPA decreased to 76.5% after reaction time 10 minutes at temperature 260℃. The products of BPA thermal decomposition were phenol and durene, etc. The result of kinetic analysis showed that BPA thermal decomposition reaction was first order and the activation energy was 32.2kJ·mol^-1.In co-solvent system, stability of DMC was influenced strongly by temperature. The recovery of DMC was only 8.6% after reaction time 10 minutes at temperature 320℃. Compared to the temperature, stability of DMC wasn't effectted by pressure visibly. The final products of DMC decomposition were carbon dioxide and methanol.In co-solvent system, stability of BPA was researched. The results indicated that in the research conditions, stability of BPA influenced by temperature obviously while slightly by pressure. The recovery of BPA decreased to 69.1% after reaction time 10 minutes at temperature 260℃. The products of BPA thermal decomposition were phenol and durene, etc.According to the results, we can know that DMC was more instability in co-solvent system because of its self-catalyzed hydrolysis, and in the two systems, the intermediate product dimethyl ether could be converted to methanol because of hydrolysis with the hydrogen ion. In the two systems, stability of BPA presented differently along with the reaction temperature, which was better in co-solvent system than that in low temperature. Contrarily, BPA was more stable in methanol system when the temperature surpassed the critical temperature of methanol.