Hydrogenative Depolymerization ofPolyesters Catalyzed by a PN³-Ruthenium Complex Using Both H₂ and EtOH as Hydrogen Sources

Abstract

Selective hydrogenativedepolymerization of polyesters to diols is regarded as a promising strategyfor plastics upcycling. However, many catalysts documented in literature stillinvolve harsh reaction conditions, such as high temperature and high H₂ pressure. In this work, we present a PN³-rutheniumcomplex catalyzed polyesters upcycling into various highly value-addeddiols under mild reaction conditions using H₂ as a hydrogen source.It is worth noting that PLA depolymerizes into 1,2-propanediol under 1 MPahydrogen pressure at ambient temperature within 2 h; the conditions are muchmilder than those of previous reports. Aromatic polyester PET degradation needsharsher reaction conditions (80 ℃, 4 MPa, 3 h). The different reactionconditions enable direct separation of the degradation products of PLA and PETmixture via sequential depolymerization, as well asmixing them with polyolefins (PE, PP, PS). More strikingly, this catalyst isalso effective for the catalytic hydrogenation of polyesters in the presence ofethanol to afford various diols, avoiding the use of harsh reaction conditionsand an expensive autoclave.

Keywords

Polyesters / Hydrogenative depolymerization / Upcycling / PN³-Ru complex / Diols

Supplementary Materials

The following supporting information can be found at: https://www.sciepublish.com/article/pii/762, Table S1. The Manufacturer and Purity of Required Chemical Reagent; Figure S1. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry11); Figure S2. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry12); Figure S3. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry13); Figure S4. Quantitative ¹³C NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 15); Figure S5. Quantitative 13C NMR spectrum (CDCl3) of PLA depolymerization (Table 1, Entry 16); Figure S6. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 17); Figure S7. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 18); Figure S8. Quantitative ¹³C NMR spectrum (CDCl₃, 25 °C) of PLA depolymerization. (Table 1, Entry 19); Figure S9. Quantitative ¹³C NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 20); Figure S10. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 21); Figure S11. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 22); Figure S12. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 23); Figure S13. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 24); Figure S14. ¹H NMR spectrum (CDCl₃) of PLA depolymerization (Table 1, Entry 25); Figure S15. ¹H NMR spectrum (CDCl₃) of PCL depolymerization (Table 2, Entry 1); Figure S16. ¹H NMR spectrum (CDCl₃) of PBS depolymerization (Table 2, Entry 2); Figure S17. ¹H NMR spectrum (CDCl₃) of PET depolymerization (Table 2, Entry 3); Figure S18. ¹H NMR spectrum (CDCl₃) of PBT depolymerization (Table 2, Entry 4); Figure S19. ¹H NMR spectrum (CDCl₃) of PHB depolymerization (Table 2, Entry 5); Figure S20. ¹H NMR spectrum (CDCl₃) of PLA, PET depolymerization (Table 2, Entry 8); Figure S21. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 1); Figure S22. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 2); Figure S23. Quantitative ¹³C NMR spectrum (CDCl₃) (Table 3, Entry 2); Figure S24. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 3); Figure S25. Quantitative ¹³C NMR spectrum (CDCl₃, 25 °C). (Table 3, Entry 4); Figure S26. Quantitative ¹³C NMR spectrum (CDCl₃, 25 °C). (Table 3, Entry 5); Figure S27. Quantitative ¹³C NMR spectrum (CDCl₃) (Table 3, Entry 6); Figure S28. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 7); Figure S29. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 8); Figure S30. Quantitative ¹³C NMR spectrum (CDCl₃) (Table 3, Entry 9); Figure S31. Quantitative ¹³C NMR spectrum (CDCl₃) (Table 3, Entry 10); Figure S32. ¹H NMR spectrum (CDCl₃) (Table 3, Entry 12); Figure S33. The possible pathway for converting PHB to butyric acid through Ru catalyst under H₂.

Acknowledgments

We express our thanks for funding support from the National Natural Science Foundation of China (nos. 22261034, 22061027), the Natural Science Foundation of Jiangxi Province (nos. 20224BAB203023, 20232ACB213008), and the Open Research Fund of State Key Laboratory of Polymer Science and Technology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (no. PPCL2024-07).

Author Contributions

Experimental designing, data collection and analysis, writing manuscript, R.W. and Y.R.; supervision, W.Y., Z.J. and C.Y.; formal analysis, R.W. and L.C.; investigation, Y.P.; editing, Y.R. and C.Y.; conceptualization, C.Y. All authors have read and agreed to the published version of the manuscript.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Funding

This work was supported by the National Natural Science Foundation of China (nos. 22261034, 22061027), the Natural Science Foundation of Jiangxi Province (nos. 20232ACB213008, 20224BAB203023), and the Open Research Fund of State Key Laboratory of Polymer Science and Technology, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (no. PPCL2024-07).

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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