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. 2018 Sep 4;3(9):10433-10441.
doi: 10.1021/acsomega.8b01978. eCollection 2018 Sep 30.

CuSO4/H2O2-Catalyzed Lignin Depolymerization under the Irradiation of Microwaves

Jinhuo Dai  1 , Gavin N Styles  1 , Antonio F Patti  1 , Kei Saito  1
Affiliations

CuSO4/H2O2-Catalyzed Lignin Depolymerization under the Irradiation of Microwaves

Jinhuo Dai et al. ACS Omega. .

Abstract

The increasing demand for renewable materials in the world has resulted in sustained efforts to utilize biomass in a better way. Lignin, a natural and abundant polymer in plants, has provided an ongoing challenge for many researchers seeking ways to better utilize this abundant resource. Here, we report a very efficient lignin depolymerization strategy with the assistant of microwave radiation. Copper sulphate (CuSO4) and hydrogen peroxide (H2O2) were used to generate hydroxyl radicals to depolymerize lignin under the irradiation of microwaves. Three different types of lignin, organosolv lignin, kraft lignin, and alkali lignin, were all successfully depolymerized using microwave irradiation at a temperature of 110 °C for 7 min. The use of 1H/13C two-dimensional nuclear magnetic resonance spectroscopy enabled the confirmation of structural changes, comparing before and after depolymerization. Liquid chromatography-mass spectrometry was used to characterize the products. Both monomers and oligomers were detected after depolymerization.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Proposed Lignin Structure with Typical Bonds
Scheme 2
Scheme 2. Two Phenolic Products from Lignin Depolymerization under Microwave Irradiation
Figure 1
Figure 1
Oxidation reaction of 1-phenylethanol.
Figure 2
Figure 2
Effect of CuSO4 dosage on the oxidation of 1-phenylethanol.
Figure 3
Figure 3
SEC chromatograms of microwave degradation of alkali lignin under different conditions: (a) different CuSO4 dosages; (b) different H2O2 dosages; and (c) different reaction times.
Figure 4
Figure 4
Different bonds in lignin detected by 2D-NMR spectroscopy.
Figure 5
Figure 5
2D-NMR spectra of alkali lignin and depolymerized alkali lignin.
Figure 6
Figure 6
LC–MS detected monomers from depolymerized lignin products.
Figure 7
Figure 7
Liquid chromatogram spectra of the extracted low-molecular-weight products from (a) depolymerized alkali lignin, (b) depolymerized kraft lignin, and (c) depolymerized organosolv lignin.
See this image and copyright information in PMC

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