Bead mill-driven acceleration in catalytic methanolysis reaction of poly(ethylene terephthalate) toward low-energy chemical recycling of polymers

Abstract

Chemical recycling of poly(ethylene terephthalate) (PET) is crucial for sustainable resource circulation. However, conventional high-temperature PET depolymerization methods suffer from high energy consumption and efficiency limitations. Here, we demonstrate that a bead milling pretreatment significantly accelerates the methanolysis at temperatures below 90 °C. The effectiveness of this pretreatment is highly dependent on the choice of bead material and solvent, as these factors influence polymer chain scission and molecular weight reduction. Gel permeation chromatography (GPC) analysis revealed that bead milling breaks down PET into lower molecular weight species, and the extent of this reduction is controllable by the solvent's affinity for PET. We also developed a one-pot process that integrates continuous bead milling and methanolysis, achieving PET depolymerization without the need for external heating. We successfully utilized this DMT for the continuous synthesis of pharmaceuticals, highlighting the potential for upcycling commodity polymers. This efficient, low-temperature depolymerization of PET significantly reduces energy consumption compared to conventional high-temperature processes, paving the way for a more environmentally friendly recycling method. This study represents a significant step towards a sustainable society in an era of increasing resource constraints and environmental concerns.