Reaction behavior of lignin in supercritical methanol as studied with lignin model compounds |
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Authors: | E?Minami H?Kawamoto Email author" target="_blank">S?SakaEmail author |
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Institution: | (1) Department of Socio-Environmental Energy Science, Graduate School of Energy Science, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan Tel. +81-75-753-4738; Fax +81-75-753-4738 e-mail: saka@energy.kyoto-u.ac.jp, JP |
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Abstract: | The reaction behavior and kinetics of lignin model compounds were studied in supercritical methanol with a batch-type supercritical
biomass conversion system. Guaiacol, veratrole, 2,6-dimethoxyphenol, and 1,2,3-trimethoxybenzene were used as model compounds
for aromatic rings in lignin. In addition, 5-5, β-1, β-O-4, and α-O-4 types of dimeric lignin model compounds were used as representatives of linkages in lignin. As a result, aromatic rings
and 5-5 (biphenyl)-type structures were stable in supercritical methanol, and the β-1 linkage was not cleaved in the β-1-type structure but converted rapidly to stilbene. On the other hand, β-ether and α-ether linkages of β-O-4 and α-O-4 lignin model compounds were cleaved rapidly, and these compounds decomposed to some monomeric compounds. Phenolic compounds
were found to be more reactive than nonphenolic compounds. These results indicate that cleavages of ether linkages mainly
contribute to the depolymerization of lignin, whereas condensed linkages such as the 5-5 and β-1 types are not cleaved in supercritical methanol. Therefore, it is suggested that the supercritical methanol treatment effectively
depolymerizes lignin into the lower-molecular-weight products as a methanol-soluble portion mainly by cleavage of the β-ether structure, which is the dominant linkage in lignin.
Received: December 19, 2001 / Accepted: April 30, 2002
Acknowledgments This research has been done under the research program for the development of technologies for establishing an ecosystem
based on recycling in rural villages for the twenty-first century from the Ministry of Agriculture, Forestry and Fisheries,
Japan; by a Grant-in-Aid for Scientific Research (B)(2) (no.12460144, 2001.4–2003.3) from the Ministry of Education, Culture,
Sports, Science and Technology, Japan; and under the research program from Kansai Research Foundation for Technology Promotion,
Japan. The authors thank them for their financial support.
This study was presented in part at the 45th Lignin Symposium, Ehime, Japan, October 2000 and the 52nd Annual Meeting of the
Japan Wood Research Society, Gifu, Japan, April 2002
Correspondence to:S. Saka |
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Keywords: | Supercritical methanol Lignin model compound β -O-4 Linkage α -O-4 Linkage β -1 Linkage 5-5 Linkage |
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