Characterization of the Interunit Bonds of Lignin Oligomers Released by Acid-Catalyzed Selective Solvolysis of Cryptomeria japonica and Eucalyptus globulus Woods via Thioacidolysis and 2D-NMR.
Acid-catalyzed degradation of lignin in toluene containing methanol selectively yields C6-C2 lignin monomers and releases lignin oligomers, a potential raw feedstock for epoxy resins. We herein characterize the structures of the lignin oligomers by focusing on the changes in the interunit linkage types during solvolysis. The oligomeric lignin products were analyzed via thioacidolysis and 2D-HSQC-NMR. The results show that lignin oligomers ranging from monomers to tetramers are released through considerable cleavage of the β-O-4 linkages. The lignin oligomers from Cryptomeria japonica (softwood) mainly comprise β-5, β-1, and tetrahydrofuran β-β linkages, whereas Eucalyptus globulus (hardwood) yields oligomers rich in β-1 and syringaresinol β-β linkages. Both wood samples exhibit selective release of β-β dimers and a relative decrease in 5-5 and 4-O-5 bonds during solvolysis. The method presented for the separation of lignin oligomers without β-O-4 linkages and with linkages unique to each wood species will be useful for the production of lignin-based materials.
Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University , Uji, Kyoto 611-0011, Japan.
Kaori
K
Saito
Nippon Kayaku Company, Ltd. , Meiji Yasuda Seimei Building 19th and 20th Floors, 1-1 Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-0005, Japan.
Atsushi
A
Kaiho
Nippon Kayaku Company, Ltd. , Meiji Yasuda Seimei Building 19th and 20th Floors, 1-1 Marunouchi 2-chome, Chiyoda-ku, Tokyo 100-0005, Japan.
Ryo
R
Sakai
Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University , Uji, Kyoto 611-0011, Japan.
Hiroshi
H
Nishimura
Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University , Uji, Kyoto 611-0011, Japan.
Hitomi
H
Okada
Laboratory of Biomass Conversion, Research Institute for Sustainable Humanosphere, Kyoto University , Uji, Kyoto 611-0011, Japan.
Takashi
T
Watanabe
D032485:Cryptomeria / Q000737:chemistry*; D005052:Eucalyptus / Q000737:chemistry*; D005663:Furans / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D017705:Lignans / Q000737:chemistry; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D014934:Wood / Q000737:chemistry*
D005663:Furans; D017705:Lignans; C042192:syringaresinol; C018674:tetrahydrofuran; D008031:Lignin
2D-NMR; degradation; guaiacyl; lignin; syringyl; thioacidolysis