Catalytic Upcycling of Waste Polyethylene Terephthalate: Recent Advances in Catalyst Design, Reaction Pathway Control, and High-Value Conversion

The catalytic upcycling of waste polyethylene terephthalate (PET) is a key strategy for both plastic recycling and the high-value conversion of carbon resources. PET has a rigid aromatic backbone, a semi-crystalline morphology, and a complex composition in real waste streams. These properties make its catalytic conversion sensitive to factors such as chemical bond activation, segment accessibility, and mass transfer limitations. This paper systematically summarizes the core scientific issues associated with the catalytic upgrading of PET through a logical research framework. The discussion covers structural characteristics, catalyst design, reaction pathway control mechanism analysis, and high-value product development. This review emphasizes the relationship between the molecular structure and reactivity of PET. It also elaborates the regulatory effects of diverse catalytic functions on selective conversion. These functions involve acid–base sites, metal sites, interfacial structures, and pore structures. Furthermore, this work illustrates the formation mechanisms of typical target products. The discussed products include ring-closed monomers, aromatic chemicals, alicyclic monomers, functionalized derivatives, and fuel precursors. By integrating in situ characterization, kinetic analysis, and theoretical calculations, this review identifies key challenges in current mechanistic research on PET catalytic upgrading. Prospective research directions are also proposed for the future development of highly efficient, stable, and scalable catalytic systems.