Selective depolymerization of polyolefin plastics into olefin monomers on electrified tungsten filament

Polyolefin plastics account for ~60% of global plastic waste, and thus depolymerizing large quantities of waste polyolefin plastics into olefin monomers is attractive for both recycling plastics in a circular economy and providing sustainable raw materials for the chemical industry. However, the selectivity of olefin monomers is limited even with catalysts. Here we report an electrified tungsten filament method for depolymerizing polyolefin plastics into olefin monomers with competitive selectivities. In this system, a high temperature zone exceeding 1000 °C enables plastic depolymerization within 1 s, while the flow field transfers the products to a zone near room temperature, preventing nonselective further conversion. For depolymerizing polyethylene to ethylene, this method achieves a selectivity of 48%, substantially improved compared with that of traditional methods, such as catalytic pyrolysis (typically <20%). Moreover, polyethylene and polypropylene of various molecular weights and their mixtures have been depolymerized with monomer selectivities of 45–58% without the formation of tars and chars. This strategy offers rich possibilities for advancing a circular economy based on waste plastics.