Cost-Effective and Low-Carbon Scalable Recycling of Waste Polyethylene Terephthalate Through Bio-Based Guaiacol-Enhanced Methanolysis

Abstract

The global plastic waste crisis, particularly from polyethylene terephthalate (PET), demands sustainable recycling solutions. PET methanolysis offers a promising route to recover high-purity dimethyl terephthalate (DMT), but achieving scalable, cost-effective, and environmentally friendly processes under mild conditions remains challenging. This study introduces a bio-based catalytic system using guaiacol and potassium bicarbonate (KHCO₃) under mild conditions (120 °C, 0.6 MPa), achieving 94% DMT and 98% ethylene glycol (EG) yields within 2 h. Unlike conventional acid-catalyzed or co-solvent-assisted methanolysis methods, the phenolic hydroxyl group of guaiacol critically stabilizes the tetrahedral intermediate, significantly enhancing catalytic efficiency. The system demonstrates broad versatility across various polyesters and real-world PET waste streams, including mixed textiles and colored plastics, while enabling selective depolymerization. Life cycle assessment (LCA) and techno-economic analysis (TEA) confirm its low carbon footprint, energy efficiency, and industrial viability. This cost-effective and scalable strategy offers a sustainable solution for PET recycling, addressing both environmental and economic challenges while advancing resource circularity in the plastic industry.