Efficient method and mechanism of depolymerization of PET under conventional heating and microwave radiation using t-BuNH2/Lewis acids
2022; Elsevier BV; Volume: 175; Linguagem: Inglês
10.1016/j.eurpolymj.2022.111388
ISSN1873-1945
AutoresNayely Trejo‐Carbajal, Karina I. Ambriz-Luna, A.M. Herrera,
Tópico(s)Polymer crystallization and properties
ResumoThe chemical stability of PET has made this commodity part of solid waste by hundreds of years in the planet. The chemical degradation of poly(ethylene terephthalate) (PET) with low energy consumption and in friendly conditions, as catalytic system, or solvents continues to be a challenge. In the present work, the chemical degradation of PET is reported using the catalytic systems t-BuNH2/LiBr and t-BuNH2/NaCl by glycolysis and hydrolysis using conventional heat and microwave radiation as energy sources. In the glycolysis reaction using the t-BuNH2/LiBr catalytic system with each of the energy sources, quantitative yields (100%) are obtained, and the lowest reaction time was ten min using microwave radiation. In the hydrolysis reaction, the best catalytic system was t-BuNH2/NaCl and using microwave radiation, quantitative yields were obtained in ten min of reaction. The catalytic system is efficient because very low concentrations are required using conventional heating and microwave radiation, obtaining only the products of interest without the presence of PET oligomers. In addition, the present work reports the depolymerization mechanism by glycolysis and hydrolysis using the catalytic systems t-BuNH2/LiBr and t-BuNH2/NaCl, proposing that from the beginning of the reaction oligomers are obtained by random breaking of the polymer chain and, depending on the reaction mechanism, these oligomers have –OH or –COO- as end groups. The characterization of the products, bis(2-hydroxyethyl) terephthalate (BHET) and terephthalic acid (TA), was carried out by NMR and FTIR, while the characterization of oligomers and PET was carried out by FTIR, viscometry and thermogravimetric analysis.
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