Recycling of poly(ethylene terephthalate) waste through methanolic pyrolysis in a microwave reactor

• Published in: Journal of analytical and applied pyrolysis 2012-11, Vol.98, p.214-220
• Main Authors: Siddiqui, Mohammad Nahid, Redhwi, Halim Hamid, Achilias, Dimitris S.
• Format: Article
• Language: English
• Subjects: bottles; catalysts; depolymerization; energy conservation; ethylene; Fourier transform infrared spectroscopy; methanol; Methanolic pyrolysis; methanolysis; Microwave irradiation; microwave radiation; PET; polyethylene terephthalates; pyrolysis; Recycling; temperature; wastes; zinc acetate
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/j.jaap.2012.09.007

► Methanolic pyrolysis of PET waste using microwave irradiation technique is one of the green technologies for the pyrolysis processes. ► The methanolic pyrolysis was carried out with and without the use of zinc acetate as catalyst. ► Effects of time, temperature and microwave power were studied. ► High degrees of depolymerization were observed at temperatures near 180°C and at microwave power higher than 150W. ► Microwave irradiation affords methanolic pyrolysis in much shorter reaction times compared to conventional pyrolysis methods. In this study, the methanolic pyrolysis (methanolysis) of poly(ethylene terephthalate) (PET) taken from waste soft-drink bottles, under microwave irradiation, is proposed as a recycling method with substantial energy saving. The reaction was carried out with methanol with and without the use of zinc acetate as catalyst in a sealed microwave reactor in which the pressure and temperature were controlled and recorded. Experiments under constant temperature or microwave power were carried out at several time intervals. The main product dimethyl-terephthalate was analyzed and identified by FTIR and DSC measurements. It was found that PET depolymerization, is favored by increasing temperature, time and microwave power. High degrees of depolymerization were measured at temperatures near 180°C and at microwave power higher than 150W. Most of the degradation was found to occur during the initial 5–10min. Compared to conventional pyrolysis methods, microwave irradiation during methanolic pyrolysis of PET certainly results in shorter reaction times supporting thus the conclusion that this method is a very beneficial one for the recycling of PET wastes.