Issue 21, 2021

Role of peracetic acid on the disruption of lignin packing structure and its consequence on lignin depolymerisation

Abstract

Peracetic acid (PAA) is an effective oxidant capable of solubilising lignin and efficiently depolymerising it to selective phenolic compounds; however, the specific role by which PAA initiates the depolymerisation is still elusive. Herein, interaction between PAA and the lignin macromolecule and the consequent structural changes of the latter were studied by characterising the lignin packing structure and its associated changes during the oxidation process. While the lignin packing structure and its changes associated with the PAA-mediated oxidation were probed by X-ray diffraction, the impact of the PAA on different chemical functionalities present in the lignin structure was established by 13C and 1H–13C heteronuclear single-quantum coherence nuclear magnetic resonance (NMR) spectroscopy. Combining the NMR spectroscopy results, and the product distribution, we conclude that the predominant reaction pathway for the oxidative depolymerisation of lignin with PAA is the Baeyer–Villiger oxidation of the ketone formed by the oxidation of the benzylic hydroxyl group adjacent to the β-O-4 linkage. The experimental evidence provided herein corroborated that PAA instigates oxygen insertion to the lignin macromolecule resulting in disruption of its packing structures and facilitates depolymerisation. We also investigated various metal oxide and mixed metal oxide catalysts to identify effective catalysts that further enhance the efficiency of PAA-mediated depolymerisation of lignin and produce selective monomeric phenolic compounds. Techno-economic analysis was also conducted to identify the key parameters associated with this oxidative process that need to be considered for possible commercial application.

Graphical abstract: Role of peracetic acid on the disruption of lignin packing structure and its consequence on lignin depolymerisation

Supplementary files

Article information

Article type
Paper
Submitted
29 Jun 2021
Accepted
24 Aug 2021
First published
03 Sep 2021

Green Chem., 2021,23, 8468-8479

Author version available

Role of peracetic acid on the disruption of lignin packing structure and its consequence on lignin depolymerisation

R. Ma, U. Sanyal, M. V. Olarte, H. M. Job, M. S. Swita, S. B. Jones, P. A. Meyer, S. D. Burton, J. R. Cort, M. E. Bowden, X. Chen, M. P. Wolcott and X. Zhang, Green Chem., 2021, 23, 8468 DOI: 10.1039/D1GC02300D

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