A comparative study of secondary depolymerization methods on oxidized lignins

Selective oxidation of lignin's β-aryl ether units combined with secondary chemical treatment for depolymerization can generate valuable oxygen-rich aromatics. Although there have been many reports of the successful oxidative depolymerization of lignin, an accurate assessment of the merits of e...

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Bibliographic Details
Published in:Green chemistry : an international journal and green chemistry resource : GC 2019-07, Vol.21 (14), p.394-3947
Main Authors: Song, Yang, Motagamwala, Ali Hussain, Karlen, Steven D, Dumesic, James A, Ralph, John, Mobley, Justin K, Crocker, Mark
Format: Article
Language:English
Subjects:
Aldehydes
Aromatic compounds
Chemical treatment
Comparative studies
Depolymerization
Gold
Green chemistry
Lignin
Monomers
Organic chemistry
Oxidation
Selectivity
Substrates
Yield
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Summary:Selective oxidation of lignin's β-aryl ether units combined with secondary chemical treatment for depolymerization can generate valuable oxygen-rich aromatics. Although there have been many reports of the successful oxidative depolymerization of lignin, an accurate assessment of the merits of each method is hampered by the wide array of lignins used. Here, we test a selection of literature methods for secondary lignin depolymerization using a common set of lignin substrates. In an initial step, the lignins were oxidized using 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ)/ tert -butyl nitrite ( t BuONO)/O 2 . The oxidized lignins were then subjected to a variety of depolymerization methods, the yield of aromatic monomers being quantified and compared to lignin depolymerized using an Au/Li-Al LDH catalyst followed by hydrolysis without prior C α -OH oxidation. The Au/Li-Al LDH system gave the highest monomer yield for the untreated lignins, moreover, for DDQ-oxidized lignins, the Au/Li-Al LDH method produced similar monomer yields with high selectivity towards aromatic acids and aldehydes. DDQ oxidized lignins were used as substrates to assess the effectiveness of secondary depolymerization methods for the production of aromatics.
ISSN:1463-9262
1463-9270
DOI:10.1039/c9gc01663e