Assessing supported nickel catalysts for the upcycling of real WEEE plastics through low-pressure hydropyrolysis and dehalogenation

Abstract

Electrical and electronic equipment waste (WEEE) is among the fastest-growing waste streams, posing recycling challenges due to its high heterogeneity and the presence of organo-halogenated compounds. Hydropyrolysis offers a promising way to convert WEEE plastics into valuable, dehalogenated organic liquids, facilitating their upcycling. This study examines catalytic hydropyrolysis at mild pressure of real WEEE plastics containing both chlorine and bromine. Nickel-based catalysts on various supports (Al₂O₃, n-ZSM-5 zeolite, SiO₂, and activated carbon (AC)) were tested in batch and continuous systems. In the thermal reaction, over 70 wt% oil was obtained, decreasing slightly with catalyst use. Char played a key role in removing halogens, retaining up to 95%, which was reinforced by the dehalogenation activity of the catalysts. While all catalysts were highly efficient for oil dehalogenation, the best performance was shown by Ni/AC. The AC support alone contributed significantly to halogen trapping, while Ni incorporation into the catalyst further enhanced the oil dehalogenation degree, allowing total Br removal and reducing its Cl content to just 9 ppm, as well as enhancing the production of valuable monoaromatic hydrocarbons. The Ni/AC catalyst exhibited high stability over time on stream when using a continuous oil feeding reaction system and could be fully regenerated by water/dioxane washing, restoring its dehalogenation capability to the level of the fresh one. This work highlights the potential of catalytic hydropyrolysis to address the environmental challenges posed by WEEE plastics, offering a sustainable alternative for their dehalogenation and upcycling into valuable chemical products.