Cooperation between Pt and Ru on RuPt/AC bimetallic catalyst in the hydrogenation of phthalates

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

Plastic waste is a promising and abundant resource for H2 production. However, upcycling plastic waste into H2 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 H2 fuel in a mild and clean manner. PP waste was first oxidized into small-molecule organic acids using pure O2 as oxidant at 190 °C, followed by the catalytic reforming of oxidation aqueous products over ZnO-modified Ru/NiAl2 O4 catalysts to produce H2 at 300 °C. A high H2 yield of 44.5 mol/kgPP and a H2 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.

Catalytic Reforming of the Aqueous Phase Derived from Diluted Hydrogen Peroxide Oxidation of Waste Polyethylene for Hydrogen Production

The thermal degradation and conversion of waste polyethylene (PE) using a two-step process including hydrothermal oxidation (HO) and aqueous phase reforming (APR) were investigated. The objective of this study was to achieve efficient disposal of waste PE and generate H₂ in a mild and green way. The effects of various HO conditions on both HO and APR processes were studied. A high H₂ O₂ concentration caused overoxidation of PE resulting in more CO₂ . Decreasing the H₂ O₂ concentration weakened the overoxidation. The process using diluted H₂ O₂ exhibited the highest selectivity for acetic acid among the produced carboxylic acids. When the HO temperature exceeded 200 °C, there was an increase in the CO₂ yield during the HO process and a decrease in the H₂ yield during the APR process. In addition, the effects of various monometallic and bimetallic catalysts on the reforming of the aqueous phase from the HO of PE were discussed. The highest H₂ mole fraction (51.52 %) in gaseous products from the APR process was obtained with Ru/mesoporous carbon. Nevertheless, Ru-Ni exhibited a higher stability than the monometallic Ru catalyst.