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| PDF : |  18010027.pdf |
| title(En) : | Change of Lignin Molecule by Alkaline Hydrolysis. On the Determination of Side Chain Length and Condensed Type Unit by NMR Spectroscopy |
| author(En) : | Noriyuki Morohoshi, Akira Sakakibara |
| information : | Mokuzai Gakkaishi 18(1), 27-35 (1972) |
| assort : | Original Article |
| summary(En) : | To find the change of lignin structure with alkaline treatment, we hydrolyzed MWL of Picea jezoensis CARR. in 30%-NaOH at 100°C, 150°C and 200°C for 0.5 hour and determined the functional groups of these degradation products and analyzed them by UV, IR and NMR spectroscopy. Phenolic hydroxyl groups of alkaline hydrolysis products determined by Js-method and total hydroxyl groups of untreated MWL determined by Hillis-method were in good agreement with those determined by NMR-method. Therefore, NMR spectroscopy can be used for determination of phenolic and total hydroxyl groups in MWL. Phenolic hydroxyl groups increased remarkably at 100°C-150°C, but not at 150°C-200°C. This indicates that cleavage of ether linkage finishes at a temperature between 100°C and 150°C. The higher the reaction temperature, the less the aliphatic hydroxyl and methoxyl groups. Aliphatic hydroxyl and methoxyl groups per C9 unit decreased by about 0.30 and 0.12, respectively. Hydrolysis at 150°C results in weight loss of about 15%, loss of about 0.7 carbon atom of side chain per monomer unit, and increase in condensed type unit in lignin from 36% to 63%. These results indicate that cleavage of ether linkage and side chain and condensation of aromatic ring occur predominantly at 100°C-150°C. We conclude that reaction mechanism suggested by model compounds with alkaline hydrolysis can be applied to alkaline hydrolysis of high molecular lignin. |