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 (tBuONO)/O2. 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 Cα-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.
|Number of pages||8|
|State||Published - 2019|
Bibliographical noteFunding Information:
This research was funded by the National Science Foundation under Cooperative Agreement No. 1355438 and by the Global Bioenergy, Biofuels, and Biorefining network (GB3-Net) supported by the British Council and the Department for Business, Innovation and Skills (BIS). SDK, JR, and JKM (in part) were funded by the DOE Great Lakes Bioenergy Research Center (DOE Office of Science BER DE-FC02-07ER64494 and DE-SC0018409). The authors thank Dr Mitra Ganewatta at Ingevity (North Charleston, SC) for providing the Indulin AT kraft lignin, as well as Dr Zhen Fang and Dr Mark Meier (University of Kentucky) for helpful discussions.
© 2019 The Royal Society of Chemistry.
ASJC Scopus subject areas
- Environmental Chemistry