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In recent years, PET depolymerization technology boomed in China, the methods of PET depolymerization are diverse, but the mechanism of it is far behind the technology. However, increasing attention to the environmental problems caused by the extensive use of PET requires us to have in-depth study of its mechanism. The study on PET depolymerization in microwave, it will not only provide the theoretical to the industrialization of PET depolymerization in microwave, but also give effective support to the non-thermal effects of microwave irradiation.This paper studied the process of PET depolymerization in pure water with microwave in different time while the water and PET mass ratio is 10:1 and the temperature are at 190℃, 180℃and 170℃. We studied the action by measure, analyse and characterize the liquid and solid residues, investigated the mechanism of PET depolymerization in microwave and established the corresponding dynamic model. By using gas chromatography (GC), infrared spectroscopy (IR), gel permeation chromatography (GPC), thermal analysis spectrometer (TG-DSC), scanning electron microscopy (SEM) and other methods, we analysed the degree of PET depolymerization and the morphology and thermotics of residues, while the energy supplied by microwave to the reaction was calculated at the same time.We used gas chromatography method to measue the consistency of ethylene glycol(EG) in the liquid residues and found that the consistency rises by the time under a certain temperature and also rises when raise the tempetature at the certain time, while the relationship between the EG consistency and time is not a simple linear function but an uneven one. After integrating the analysis result of gas chromatography (GC), infrared spectroscopy (IR), gel permeation chromatography (GPC), thermal analysis spectrometer (TG-DSC), scanning electron microscopy (SEM) and other methods, we concluded that the fracture of long molecular chains in PET depolymerization in micrwave has two process, while one is random and the other is regular. At the early stage of the reaction random fracture is the main one when the regular fracture is not clear, but in the later stage regular fracture is the main one. By analyzing the energy provided by microwave in the reaction, we found that the amount of microwave energy and the degree of PET depolymerization are some related, and we established the function model of microwave energy.We have optimizated the former kenetics model of the PET depolymerization, established the corresponding reaction rate equation and calculated the speed constant and the activation energy of the chemical reaction. The result indicated that under the microwave environment the activation energy of the PET depolymerization was lower than other ways, front the union the analysis obtains under the microwave the PET random depolymerization process, showing is precisely the microwave non-thermal reaction causes PET to have the random depolymerization, responded that in a short time produces the massive depolymerization product, change the way of reaction, easier the reaction. .
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