Mechanistic Insights Enable Divergent Product Selectivity in Catalyst-Controlled Photooxidative Degradation of Polystyrene

Sewon Oh, Erin E. Stache

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Polystyrene upcycling to valuable commodity feedstocks is essential for reducing plastic waste. Photooxidative degradation has emerged as a method for converting polystyrene to oxidized aromatic compounds. Investigating the mechanism of photooxidative degradation is essential for understanding the pathways to generating different small molecules. Here, we leveraged the reactivity differences between chlorine and bromine radicals to study the degradation mechanism of polystyrene. While degradation with chlorine radical yields primarily benzoic acid (50 mol %), bromine radical shows an increased preference for acetophenone (4 mol % for both products). After conducting several mechanistic studies, we discovered that activation of 3° C-H bonds is necessary to form acetophenone. However, for acetophenone production, a second hydrogen atom transfer from H-Br enables the reformation of a methyl group on the polymer chain end. Lastly, with the mechanistic insights in hand, we added exogenous bromine sources to increase the concentration of HBr and improved the acetophenone yield, becoming the major degradation product. We envision that our insights into the polystyrene degradation mechanism will further enable divergent product selectivity.

Original languageEnglish (US)
Pages (from-to)10968-10975
Number of pages8
JournalACS Catalysis
Volume13
Issue number16
DOIs
StatePublished - Aug 18 2023
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry

Keywords

  • halogen radicals
  • hydrogen atom transfer
  • photooxidative degradation
  • polymer upcycling
  • selective C−H abstraction

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