The large-scale production of non-degradable plastic waste calls for effective catalytic upcycling processes. Hydrogenolysis over Ru-based catalysts has been proven to be a viable strategy to upcycle polyolefin plastics into valuable small hydrocarbons, and highly dispersed Ru species on CeO2 exhibits unique efficiency. This poster presents how the support regulates the performance of highly dispersed Ru catalysts in this process. Combining detailed kinetic tests with comprehensive in-situ characterization, we show that the morphology of the ultra-small Ru clusters is highly dependent on the nature of the support, which drastically impacts their catalytic efficiency and selectivity in hydrogenolysis. Similar levels of activity and selectivity with CeO2 can be achieved on rutile TiO2 and fumed SiO2, while the three-dimensional Ru structure on anatase TiO2 and activated carbon leads to negligible activity. Meanwhile, the presence of Brønsted acidity on a sol-gel anatase TiO2 support opens the hydrocracking pathway, which offers higher catalytic efficiency, more desired product distribution, and can be catalyzed by non-noble metals such as Ni. The reaction network involving simultaneous, competitive hydrogenolysis and hydrocracking was evaluated under different reaction conditions, and the origins of the unexpected Brønsted acidity on the TiO2 support was revealed. This work demonstrates how the support can affect the performance of highly dispersed Ru catalysts by regulating the morphology of Ru clusters and/or offering acid functionality. It leads to new improvement and development in plastic upcycling catalysts, while offering valuable insights on the structure-function relationship and reaction mechanisms.

Support effects on the upcycling of polyolefin plastics through catalytic hydro-conversion over highly dispersed Ru catalysts

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