Recent Advancements in Pyrolysis of Halogen-Containing Plastics for Resource Recovery and Halogen Upcycling: A State-of-the-Art Review

Abstract

Plastic waste has emerged as a serious issue due to its impact on environmental degradation and resource scarcity. Plastic recycling, especially of halogen-containing plastics, presents challenges due to potential secondary pollution and lower-value implementations. Chemical recycling via pyrolysis is the most versatile and robust approach for combating plastic waste. In this Review, we present recent advancements in halogen-plastic pyrolysis for resource utilization and the potential pathways from "reducing to recycling to upcycling" halogens. We emphasize the advanced management of halogen-plastics through copyrolysis with solid wastes (waste polymers, biomass, coal, etc.), which is an efficient method for dealing with mixed wastes to obtain high-value products while reducing undesirable substances. Innovations in catalyst design and reaction configurations for catalytic pyrolysis are comprehensively evaluated. In particular, a tandem catalysis system is a promising route for halogen removal and selective conversion of targeted products. Furthermore, we propose novel insights regarding the utilization and upcycling of halogens from halogen-plastics. This includes the preparation of halogen-based sorbents for elemental mercury removal, the halogenation−vaporization process for metal recovery, and the development of halogendoped functional materials for new materials and energy applications. The reutilization of halogens facilitates the upcycling of halogen-plastics, but many efforts are needed for mutually beneficial outcomes. Overall, future investigations in the development of copyrolysis and catalyst-driven technologies for upcycling halogen-plastics are highlighted.

Ionic liquids as a shuttle for releasing and capturing hydrogen chloride: a new way to utilize waste HCl generated in organic reactions

“…2–4 At present, this is mostly focused on the recovery or comprehensive utilization of wastes produced from a concrete chemical process. 5–8 However, few studies based on the potential reaction ability and special properties of wastes are reported.…”

Recent Trends of Recycling and Upcycling of Polymers and Composites: A Comprehensive Review

“…Several advancements have been achieved regarding the pyrolysis of halogen-plastics for resource recovery and potential routes for upcycling of halogens [213]. Microwave heating, plasma or electron beam irradiation, and supercritical pyrolysis are newly emerging industrially relevant technologies available for the dechlorination or breakdown of chlorinated plastics.…”