Highly selective upcycling of plastic mixture waste by microwave-assisted catalysis over Zn/b-ZnO

Abstract

7 billion of 9.2 billion tons of plastic produced becomes waste while conventional catalytic plastic recycling methods are vulnerable with degraded performance and intensive energy input. Here, a hybrid Zn/b-ZnO catalyst, together with the specially-designed microwave reaction system, has achieved fast plastic waste upgrading under atmospheric pressure without using H₂. Bifunctional ZnO acts as a microwave absorber and substrate catalyst, and in-situ formed Zn clusters promote C-C bond cleavage and nearly 100% upcycle landfilled plastic mixtures into lubricant base oil precursors and monomers. Unprecedented turnover number (250 g_plastic g⁻¹_catalyst) of plastic depolymerisation and long-time stability over 50 successive cycles have been demonstrated, together with 8-time higher energy efficiency compared with conventional catalysis, indicating this strategy is an economical approach to efficient upcycling of plastics towards valuable products. Moreover, the catalyst can tolerate high contaminates, even the landfilled plastics can still be converted to lubricant base oil precursors, which has never been reported before.