Ternary-Active NiO–NiAl2O4–Al2O3 Nanocomposite for Selective Upcycling of Polypropylene into Liquid Branched Olefins

Chemical upcycling is an attractive platform for converting plastic waste into valuable products. Here, a tandem deconstruction–catalysis route was developed for upcycling polypropylene (PP). A ternary-active NiO–NiAl₂O₄–Al₂O₃ nanocomposite was innovatively synthesized, with the NiO/NiAl₂O₄ particle size lowering to ca. 5 nm, affording abundant active sites. Importantly, it demonstrated excellent reusability, maintaining high catalytic activity over 30 cycles with the highest liquid yield of 63.33 wt %, primarily composed of branched olefins. Particularly, it was capable of effectively upcycling real-world PP medical operating coats, achieving a narrower carbon number distribution with exceptionally high carbon selectivity of 90.18 mol % for gasoline (C₄–C₁₂)-range hydrocarbons, respectively. Additionally, in situ Fourier transform infrared spectroscopy characterization revealed that the ternary-active nanocomposite facilitated the activation and pre-cracking of PP chains into shorter, unsaturated oligomers, which were subsequently converted into branched olefins and aromatics. In brief, this study proposed a promising solution using a ternary-active nanocomposite to effectively upcycle PP waste.