Efficient and selective dual-pathway polyolefin hydro-conversion over unexpectedly bifunctional M/TiO2-anatase catalysts

The huge scale of plastic waste generation and its environmental consequences drive the demands for catalytic plastic upcycling processes. Here, we report efficient polypropylene (PP) hydro-conversion over Ru and Ni supported on a sol-gel anatase TiO2 (TiO2-A-SG). A small number of Brønsted acid sit...

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Bibliographic Details
Published in:Applied catalysis. B, Environmental Environmental, 2023-10, Vol.335 (C), p.122897, Article 122897
Main Authors: Chen, Linxiao, Moreira, Julia B., Meyer, Laura C., Szanyi, János
Format: Article
Language:English
Subjects:
Anatase titania
Hydrocracking
Hydrogenolysis
Plastic upcycling
Polyolefin
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Summary:The huge scale of plastic waste generation and its environmental consequences drive the demands for catalytic plastic upcycling processes. Here, we report efficient polypropylene (PP) hydro-conversion over Ru and Ni supported on a sol-gel anatase TiO2 (TiO2-A-SG). A small number of Brønsted acid sites on TiO2-A-SG enables hydrocracking, improving efficiency, steering the selectivity towards high-valued C4–20, and allowing more isomerization, compared to Ru-based monofunctional hydrogenolysis catalysts. The relative contribution of hydrocracking increases with lower hydrogen partial pressure, more branched substrates, and lower Ru loading. Ni/TiO2-A-SG exhibits superior hydrocracking activity and selectivity to Ni on conventional Brønsted-acidic supports, particularly zeolites. Mechanistic studies shows fast isomerization and sequential β-scissions caused by strong polymer-catalyst interaction and fast cracking with abundant 3C. This favors C4–12 formation and prevents secondary reactions. This work demonstrated a novel, highly efficient noble-metal-free catalyst for plastic waste upcycling, while advancing the mechanistic understanding of polyolefin hydro-conversion. [Display omitted] •Low-population Brønsted-acid sites on M/TiO2-A-SG catalyzing PO hydrocracking.•Hydrocracking improving efficiency and selectivity over Ru-catalyzed hydrogenolysis.•High PH2 and substrate branching level favoring hydrocracking over hydrogenolysis.•TiO2-A-SG more efficient in PO hydrocracking than SiO2-Al2O3-based supports.•Strong adhesion of polymers affecting the product selectivity and mechanisms.
ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2023.122897