Visible-light-driven photocatalytic depolymerization of post-consumer PET to terephthalic acid via cerium catalysis with batch-to-flow scalability

Abstract

Polyethylene terephthalate (PET), as one of the five major engineering plastics with an annual production exceeding 80 million metric tons, has created escalating environmental challenges. Currently, approximately 79% of discarded PET is treated through landfill or incineration, while conventional chemical recycling technologies (e.g., hydrolysis and alcoholysis) require harsh conditions such as high temperature, high pressure, and highly corrosive media, leading to issues including high energy consumption, severe equipment corrosion, and secondary pollution. This study pioneers a cerium-based photocatalytic system, achieving for the first time the efficient depolymerization of PET waste under visible-light-driven conditions. At ambient temperature and pressure, the cerium trichloride (CeCl₃) photocatalyst activates visible light to depolymerize post-consumer PET (including plastic bottles and textile fibers) into high-purity terephthalic acid (PTA) without requiring strong alkali pretreatment, overcoming the equipment corrosion challenges inherent in conventional photocatalytic reforming technologies that rely on concentrated alkaline solutions. An innovatively designed microchannel reactor system leverages its high surface-to-volume ratio to enhance light utilization efficiency while resolving optical path decay issues, providing an engineered solution for large-scale processing. This breakthrough establishes a sustainable pathway for PET circular economy, addressing critical limitations of existing physical and chemical recycling methods.