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

Julie Rorrer, Clara Troyano-Valls, Gregg Beckham, Yuriy Roman-Leshkov

Research output: Contribution to journalArticlepeer-review

118 Scopus Citations

Abstract

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 (Mw ∼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.

Original languageAmerican English
Pages (from-to)11661-11666
Number of pages6
JournalACS Sustainable Chemistry and Engineering
Volume9
Issue number35
DOIs
StatePublished - 6 Sep 2021

Bibliographical note

Publisher Copyright:
©

NREL Publication Number

  • NREL/JA-2A00-80249

Keywords

  • Depolymerization
  • Hydrogenolysis
  • Mixed plastics
  • Plastic upcycling
  • Polyethylene
  • Polypropylene
  • Ruthenium

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