Processo sustentável de glicólise de pet pós-consumo : estudo da reutilização do catalisador, etilenoglicol e água

Abstract

Poly (ethylene terephthalate), PET, is one of the most used plastics worldwide, mostly used in short-life packaging, such as soda and mineral water bottles. However, the irregular disposal of this material after consumption has caused enormous environmental and economic problems. Recently, the search for ecologically correct alternatives has intensified, among them chemical recycling (glycolysis method) is a technologically attractive option. The objective of this work was to study the post-consumer PET depolymerization reaction catalyzed by titanate nanotubes (TNT) and to evaluate the reusability of the TNT catalyst and the recovery and reuse of ethylene glycol (EG) and water. The TNT catalyst was characterized using MEV-FEG, TEM, DRX and FTIR techniques, while BHET was characterized by FTIR, NMR and DSC. The glycolysis reactions were carried out taking into account the following reaction parameters: EG/PET mass ratio of 4:1, PET/catalyst mass ratio of 300:1, reaction time of 3 hours and temperature of 196 °C. After the hot filtration, the mixture of oligomers and TNT was dried and added in a new reaction. Residual water and EG were separated under reduced pressure at 60 °C and recovered to be inserted in a new glycolysis reaction. The recovery of EG and water was done using a rotary evaporator and reached values of 70% and 80%, respectively. Recovered EG showed moisture < 1%, while recovered water maintained pH close to neutrality and electrical conductivity around 4-7 μS/cm. It was achieved 100% PET conversion and the yield in BHET was on average 75% in the reuse reactions of TNT, EG and water.