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

Publication History

Received: 14 September 2023

Accepted after revision: 30 October 2023

Accepted Manuscript online:
30 October 2023

Article published online:
03 January 2024

• References and Notes

• 1a Plastics–The Facts. An Analysis of European Plastics Production, Demand and Saste Data. Plastics Europe; Brussels: 2022. https://plasticseurope.org/knowledge-hub/plastics-the-facts-2022/
• 1b Manos G. Feed-stock Recycling and Pyrolysis of Waste Plastics: Converting Waste Plastics into Diesel and Other Fuels. John Wiley and Sons Ltd; Weinheim: 2006
• 1c Strom ET, Rasmussen SC. 100+ Years of Plastics. Leo Baeke-land and Beyond 2011
• 1d Roland G, Jenna RJ, Kara LL. Production, Use, and Fate of all Plastics ever Made, Sci. Adv. 2017; 3: e1700782
• 2a Kim HR, Lee HM, Yu HC, Jeon E, Lee S, Li J, Kim D.-H. Environ. Sci. Technol. 2020; 54: 6987
• 2b Jenna RJ, Roland G, Chris W, Theodore RS, Miriam P, Anthony A, Ramani N, Kara LL. Science 2015; 347: 768
• 2c Aljabri NM, Lai Z, Hadjichristidis N, Huang K.-W. J. Saudi Chem. Soc. 2017; 21: 983
• 3a Frediani F, Undri A, Rosi L, Frediani M. Waste/Contaminated Polystyrene Recycling through Reverse Polymerization in Polystyrene: Synthesis, Characteristics and Applications, Chap. 1. Nova Publishers; New York: 2014
• 3b Maafa IM. Polymers 2021; 13: 225
• 3c Balakrishnan RK, Guria C. Polym. Degrad. Stab. 2007; 92: 1583
• 3d Ivanova SR, Gumerova EF, Minsker KS, Zaikov GE, Berlin A. Prog. Polym. Sci. 1990; 15: 193
• 3e Karmore V, Madras G. Ind. Eng. Chem. Res. 2002; 41: 657
• 3f Nanbu H, Sakuma Y, Ishihara Y, Takesue T, Ikemura T. Polym. Degrad. Stab. 1987; 19: 61
• 3g Marczewski M, Kamioska E, Marczewska H, Godek M, Rokicki G, Sokołowski J. Appl. Catal., B 2013; 129: 236
• 4a Audisio G, Beriti F. J. Anal. Appl. Pyrolysis 1992; 24: 61
• 4b Onwudili JA, Insura N, Williams PT. J. Anal. Appl. Pyrolysis 2009; 86: 293
• 4c Undri A, Frediani M, Rosi L, Frediani P. J. Anal. Appl. Pyrolysis 2014; 105: 35
• 5a Lei Y, Lei H, Huo J. Polym. Degrad. Stab. 2015; 118: 1
• 5b Feng H.-M, Zheng J.-C, Lei N.-Y, Yu L, Kong KH.-K, Yu H.-Q, Lan T.-C, Lam MH. W. Environ. Sci. Technol. 2014; 45: 744
• 5c Shang J, Chai M, Zhu Y. Environ. Sci. Technol. 2003; 37: 4494
• 5d Ward CP, Armstrong CJ, Walsh AN, Jackson JH, Reddy CM. Environ. Sci. Technol. Lett. 2019; 6: 669
• 6a Zhang G, Zhang Z, Zeng R. Chin. J. Chem. 2021; 39: 3225
• 6b Zhang Z, Zhang G, Xiong N, Xue T, Zhang J, Bai L, Guo Q, Zeng R. Org. Lett. 2021; 23: 2915
• 7a Wang M, Wen J, Huang Y, Hu P. ChemSusChem 2021; 14: 5049
• 7b Oh S, Stache EE. J. Am. Chem. Soc. 2022; 144: 5745
• 7c Oh S, Stache EE. ACS Catal. 2023; 13: 10968
• 7d Huang Z, Shanmugam M, Liu Z, Brookfield A, Bennett EL, Guan R, Vega Herrera DE, Lopez-Sanchez JA, Slater AG, McInnes EJ. L, Qi X, Xiao J. J. Am. Chem. Soc. 2022; 144: 6532
• 7e Li T, Vijeta A, Casadevall C, Gentleman AS, Euser T, Reisner E. ACS Catal. 2022; 12: 8155
• 7f Qin Y, Zhang T, Ching HY. V, Raman GS, Das S. Chem 2022; 8: 2472
• 7g Cao R, Zhang M.-Q, Hu C, Xiao D, Wang M, Ma D. Nat. Commun. 2022; 13: 4809
• 7h Meng J, Zhou Y, Li D, Jiang X. Sci. Bull. 2023; 68: 1522
• 8a Balzani V, Ceroni P, Juris A. Photochemistry and Photophysics: Concepts, Research, Applications. John Wiley & Sons; Weinheim: 2014
• 8b Shields BJ, Doyle AG. J. Am. Chem. Soc. 2016; 138: 12719
• 8c Ackerman LK. G, Alvarado JI. M, Doyle AG. J. Am. Chem. Soc. 2018; 140: 14059
• 8d Deng H.-P, Fan X.-Z, Chen Z.-H, Xu Q.-H, Wu J. J. Am. Chem. Soc. 2017; 139: 13579
• 8e Deng H.-P, Zhou Q, Wu J. Angew. Chem. Int. Ed. 2018; 57: 12661
• 8f Kang YC, Treacy SM, Rovis T. ACS Catal. 2021; 11: 7442
• 8g Treacy SM, Rovis T. J. Am. Chem. Soc. 2021; 143: 2729
• 8h Xue T, Zhang Z, Zeng R. Org. Lett. 2022; 24: 977
• 8i Guo J.-J, Hu A, Chen Y, Sun J, Tang H, Zuo Z. Angew. Chem. Int. Ed. 2016; 55: 15319
• 8j Hu A, Guo J.-J, Pan H, Zuo Z. Science 2018; 361: 668
• 8k Li G, Yang L, Liu J.-J, Zhang W, Cao R, Wang C, Zhang Z, Xiao J, Xue D. Angew. Chem. Int. Ed. 2021; 60: 5230
• 8l Zhang Z, Xue T, Han Z, Zeng R. Synthesis 2023; 55: 433
• 9a Zhang X, Zeng R. Org. Chem. Front. 2022; 9: 4955
• 9b Zhang Z, Li X, Zhou D, Ding S, Wang M, Zeng R. J. Am. Chem. Soc. 2023; 145: 7612
• 9c Zhang Z, Zhang Y, Zeng R. Chem. Sci. 2023; 14: 9374
• 10a XIong N, Li Y, Zeng R. ACS Catal. 2023; 13: 1678
• 10b Wang K, Zeng R. Org. Chem. Front. 2022; 9: 3692
• 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).