Hydrogenolysis of Polypropylene and Mixed Polyolefin Plastic Waste over Ru/C to Produce Liquid Alkanes

Catalytic depolymerization of polyolefins is a promising chemical recycling strategy to create value-added products from waste plastics, which are accumulating in landfills and the natural environment at unsustainable rates. The cleavage of strong C–C bonds in polyolefins can be performed using a no...

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Bibliographic Details
Published in:ACS sustainable chemistry & engineering 2021-09, Vol.9 (35), p.11661-11666
Main Authors: Rorrer, Julie E, Troyano-Valls, Clara, Beckham, Gregg T, Román-Leshkov, Yuriy
Format: Article
Language:English
Subjects:
catalytic depolymerization
chemical recycling
hydrogenolysis
INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
mixed polyolefin waste
ruthenium heterogeneous catalyst
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Summary:Catalytic depolymerization of polyolefins is a promising chemical recycling strategy to create value-added products from waste plastics, which are accumulating in landfills and the natural environment at unsustainable rates. The cleavage of strong C–C bonds in polyolefins can be performed using a noble metal and hydrogen via a hydrogenolysis mechanism. Previously, we identified ruthenium nanoparticles supported on carbon (Ru/C) as a highly active heterogeneous catalyst for the conversion of polyethylene into liquid and gaseous n-alkanes under mild conditions. In the present study, we investigated the catalytic depolymerization of polypropylene (PP) under mild conditions (200–250 °C, 20–50 bar H2). We demonstrate that Ru/C produces C5–C32 iso-alkane yields above 68% in the absence of solvent and identify trade-offs between product yield and temperature, hydrogen pressure, and reaction time. We apply a rigorous analytical method to quantify all liquid and gaseous alkane products. The characterized catalyst was found to be recyclable after the complete depolymerization of high molecular weight PP (M w ∼ 340,000 Da) to liquid and gaseous hydrocarbons and after depolymerization of a postconsumer PP centrifuge tube. Further, the catalyst was shown to be effective in depolymerizing a mixture of high-density polyethylene and PP to produce a mixture of linear and branched liquid alkanes, demonstrating feasibility for the depolymerization of streams of mixed polyolefin waste.
ISSN:2168-0485
2168-0485
DOI:10.1021/acssuschemeng.1c03786