An effective strategy for degrading waste PET plastic into regenerated DMT with nearly equivalent methanol at relatively low temperature

The increase in the usage of polyethylene terephthalate (PET) leads to the generation of a large amount of waste, which may cause carbon emissions and waste of petroleum resources. The methanolysis method has attracted global attention, but limited by high reaction temperature and excessive use of methanol. We report here an efficient catalyst, tetramethylguanidine/1,5-diazabicyclo[4.3.0]-5-non-ene (TMG/DBN), converting waste PET into regenerated dimethyl terephthalate (rDMT) under 100 °C with almost equivalent methanol, achieving 100 % PET conversion and 93.1 % yield of rDMT. A series of analytical methods and theoretical calculations were used to reveal the enhanced interaction between the catalyst and reactants, which facilitates the degradation of PET at low methanol dosages. In addition, a kinetic model was also developed with a relatively low activation energy of 84.9 kJ/mol. This work provides an effective strategy for the up-grading recycling of waste PET under mild reaction conditions.