Enabling resource circularity through thermo-catalytic and solvent-based conversion of waste plastics

The recent rise in plastic pollution has led to a growing environmental burden, motivating new and effective methods for circular repurposing of “end-of-use” plastics. In this review, we highlight recent advances in thermochemical and catalytic pathways toward circularity of plastics utilization; specifically, hydroconversion, solvent conversion, and catalytic conversion without solvent or gaseous reagent. We present advances in the design of supported metal catalysts (Pt, Ru, Zr) for the hydroconversion of plastics, especially polyolefins (POs) and polyesters. We deduce mechanistic insights from hydroconversion reactions toward realizing economic circularity. We also review two solvent treatments: solvolysis of condensation polymers and solvent extraction for composite polymers. Last, we discuss advances in hydrocarbon conversion, without solvent or gaseous reagent, to catalytically depolymerize POs. We highlight the challenges and envision the path forward in optimal catalyst and process design that will enable the development of chemical upcycling technologies for building a circular plastic economy.