Green Production of Para-Dioxanone for Sustainable Polymers.

In recent years, para-dioxanone (PDO) has gained increasing attention due to its broad applications in biomedical materials, pharmaceuticals, and biodegradable plastics. Although dehydrogenation of diethylene glycol (DEG) has been proposed and validated, its larger implementation still suffers from high thermal-energy demand. In this context, liquid-phase oxidative lactonization of DEG and closed-loop depolymerization/recycling of poly(para-dioxanone) (PPDO) are promising directions for sustainable PDO production. Various metal catalysts (e.g., Ru, Pt, Au, Pd, Cu, and Zn) have been developed in this area; however, mechanisms, structure-function relationships, catalyst stability, and scale-up feasibility remain debatable. Therefore, this focused review critically discusses advances in eco-efficient synthesis and recovery of PDO, with emphasis on route comparison, catalyst design, stability/recovery issues, and mechanistic evidence for DEG oxidative lactonization and related diol transformations. The aim of this work is to provide scientific and technological insights into value-added lactones and circular polyester systems for the future polyester industry.