Synergistic catalysis for promoting selective C-C/C-O cleavage in plastic waste: structure-activity relationship and rational design of heterogeneous catalysts for liquid hydrocarbon production.

Ever-increasing consumption of plastic products and poor waste management infrastructure have resulted in a massive accumulation of plastic waste in environments, causing adverse effects on climate and living organisms. Although contributing ∼10% towards the total plastic waste management infrastructure, the chemical recycling of plastic waste is considered a viable option to valorize plastic waste into platform chemicals and liquid fuels. Among the various chemical upcycling processes, catalytic hydroprocessing has attracted interest due to its potential to offer higher selectivity than other thermal-based approaches. Heterogeneous catalytic hydroprocessing reactions offer routes for converting plastic waste into essential industrially important molecules. However, the functional group similarities in the plastic polymers frequently constrain reaction selectivity. Therefore, a fundamental understanding of metal selection for targeted bond activation and plastic interaction on solid surfaces is essential for catalyst design and reaction engineering. In this review, we critically assess the structure-activity relationship of catalysts used in the hydroprocessing of plastic waste for the selective production of liquid hydrocarbons. We discuss the significance of C-C/C-O bond activation in plastic waste through active site modulation and surface modification to elucidate reaction networks and pathways for achieving selective bond activation and cleavage. Finally, we highlight current challenges and future opportunities in catalyst design to upcycle real-life plastic waste and produce selective liquid hydrocarbons.