过渡金属Mn取代多金属氧簇催化醇解废旧PET

Transition metal Mn substitutes polyoxometalates for catalytic alcoholysis of waste PET

合成了一种具有三明治结构的过渡金属Mn取代的多金属氧簇(POMs)催化剂Na12[WZnMn2(H2O)2(ZnW9O34)2],用于催化聚对苯二甲酸乙二醇酯(PET)的醇解过程,对反应温度、反应时间和催化剂量等实验条件进行了优化。结果表明,在催化剂量为PET质量的1.0%、质量比PET/EG(乙二醇)为1:4及190℃的条件下反应80 min,PET降解率可达100%,对苯二甲酸乙二醇酯(BHET)的收率达84.42%。

Poly(ethylene terephthalate)(PET) is a kind of thermoplastic polymer resin and has been widely used in many fields because of its excellent thermodynamics and mechanics performance, such as synthetic fiber, plastic film, food packaging, water and soft-drink bottles and so on. However, with the extensive use of PET materials and their inherently hard-to-degrade characteristics, our environment is facing significant challenges in environmental protection and resource reuse. Therefore, it is verynecessary to carry out research on the recycling of PET. The recycling methods for PET are mainly divided into physical and chemical methods. Since chemical methods can degrade PET into raw materials and then reuse them, these methods have received more and more attention. Alcoholysis is a relatively mild method in chemical methods with the advantages of mild reaction conditions and easy separation of products. In order to achieve rapid and gentle degradation of PET and to obtain high conversion and selectivity, ethylene glycol was chosen as a solvent and polyoxometalate(POM) as catalysts for degradation of waste PET. In this study, a kind of transition-metal-substituted POM Na12[WZnMn2(H2 O)2(ZnW9 O34)2] with a sandwich structure was synthesized and it was used to catalyst the alcoholysis of poly(ethylene terephthalate)(PET). The effects of reaction time, reaction temperature, and the amount of catalyst on PET degradation were researched, the conditions was optimized. The results showed that PET could be 100% degraded at 190℃ for 80 min under the conditions of catalyst amount was 1.0 wt% of PET and mass ratio of PET to ethylene glycol(EG) was 1:4, the yield of bis(hydroxyethyl) terephthalate(BHET) achieved 84.42%. In addition, in order to determine the structure and properties of the degradation products, the degradation products were characterized by NMR, IR, TGA, DSC, HPLC and other instruments. The final experimental results showed that the catalyst can efficiently catalyze the alcoholysis reaction of PET and obtain high-purity BHET products.