Low-Temperature Upcycling of Polypropylene Waste into H₂ Fuel via a Novel Tandem Hydrothermal Process

Plastic waste is a promising and abundant resource for H-2 production. However, upcycling plastic waste into H-2 fuel via conventional thermochemical routes requires relatively considerable energy input and severe reaction conditions, particularly for polyolefin waste. Here, we report a tandem strategy for the selective upcycling of polypropylene (PP) waste into H-2 fuel in a mild and clean manner. PP waste was first oxidized into small-molecule organic acids using pure O-2 as oxidant at 190 degrees C, followed by the catalytic reforming of oxidation aqueous products over ZnO-modified Ru/NiAl2O4 catalysts to produce H-2 at 300 degrees C. A high H-2 yield of 44.5 mol/kg(PP) and a H-2 mole fraction of 60.5 % were obtained from this tandem process. The entire process operated with almost no solid residue remaining and equipment contamination, ensuring relative stability and cleanliness of the reaction system. This strategy provides a new route for low-temperature transforming PP and improving the sustainability of plastic waste disposal processes.