Enabling the Circular Economy through Chemical Recycling and Upcycling of End-of-Use Plastics

Widespread plastic pollution has led to an environmental crisis, motivating new and effective methods for recycling and upcycling “end-of-use” plastics. In this review, we highlight recent advances in chemical recycling and upcycling pathways, namely, hydroconversion, pyrolysis, and solvent treatment for the deconstruction and valorization of post-consumer plastics. We highlight the advances in the design of supported metal catalysts (Pt, Ru, Zr), for the hydroconversion of plastics, especially polyolefins (PO) and polyesters. We deduce mechanistic insights by comparing and contrasting small alkane and PO hydroconversion reactions. We also review the two types of solvent treatments: chemical solvent treatment (solvolysis) for condensation polymers and solvent extraction for composite polymers. Further, we discuss advances in pyrolysis and cross alkane metathesis to deconstruct POs into liquid hydrocarbons, and finally, the functionalization of POs into vitrimers and adhesives. 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.