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. Further, mechanistic studies shows fast isomerization and sequential ß-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.
@article{osti_2217343,
author = {Chen, Linxiao and Moreira, Julia B. and Meyer, Laura C. and Szanyi, János},
title = {Efficient and selective dual-pathway polyolefin hydro-conversion over unexpectedly bifunctional M/TiO<sub>2</sub>-anatase catalysts},
annote = {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. Further, mechanistic studies shows fast isomerization and sequential ß-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.},
doi = {10.1016/j.apcatb.2023.122897},
url = {https://www.osti.gov/biblio/2217343},
journal = {Applied Catalysis. B, Environmental},
issn = {ISSN 0926-3373},
volume = {335},
place = {United States},
publisher = {Elsevier},
year = {2023},
month = {05}}
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division (CSGB)