FeCl₃-Catalyzed Aerobic Oxidative Degradation of Polystyrene to Benzoic Acid: Scope and Mechanism

Abstract

Chemical upcycling of polystyrene (PS) is one of the most promising approaches to plastic waste reuse and to achieve economic development goals. However, it remains a huge challenge because PS has only chemically inert covalent bonds. As part of an ongoing study, we herein describe the development, scope, and mechanism of photoinduced iron catalysis for the selective oxidative degradation of polystyrene to benzoic acid. A series of commonly found polystyrene products could be degraded to benzoic acid efficiently. A plausible mechanism involving radical-based stepwise aerobic oxidation was proposed.

Key words

polystyrene - degradation - iron catalysis - photocatalysis - plastic upcycling

Publikationsverlauf

Eingereicht: 14. September 2023

Angenommen nach Revision: 30. Oktober 2023

Accepted Manuscript online:
30. Oktober 2023

Artikel online veröffentlicht:
03. Januar 2024

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• 11 Polystyrene Degradation to Benzoic acid; General Procedure To a 10 mL Schlenk tube were added FeCl₃ (0.04 mmol), TBACl (0.04 mmol), polystyrene powder (0.40 mmol of repeat unit), CCl₃CH₂OH (0.077 mmol), and acetone (4.0 mL). After switching the atmosphere to O₂ (1 atm), under irradiation at 390 nm LEDs, the resulting mixture was stirred for 120 h at room temperature. Evaporation and flash chromatography on silica gel afforded benzoic acid (PE/EtOAc, 10:1 to 5:1) as a white solid. ¹H NMR (400 MHz, CDCl₃): δ = 11.65 (brs, 1 H, -COOH), 8.14 (d, J = 7.8 Hz, 2 H, Ar-H), 7.63 (t, J = 7.4 Hz, 1 H, Ar-H), 7.49 (t, J = 7.5 Hz, 2 H, Ar-H).