Role of Syringyl Moieties in Kraft Delignification of Hardwood
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In order to elucidate the role of syringyl moieties in kraft delignification of hardwood, kraft pulping of Douglas-fir (Pseudotsuga menziesii) and sweetgum (Liquidambar styraciflua) was carried out from 90℃ to a final temperature of 170℃ at a heating rate of 1℃/min. At various stages of delignification, the structures of pulp residual lignins were analyzed by a combination of nucleus exchange and nitrobenzene oxidation. Syringyl moieties were revealed to facilitate the delignification of hardwood in the followingmanner: (a) Syrineyl units induce the flexibility of lignin molecule because of high frequency ofβ-O-4 linkages. (b) Syringyl units are easily dissolved because of no condensed type linkages and no reactive sites on the nuclei for condensation reactions. (c) Syringyl units accelerate the cleavage of β-O-4 linkages,resulting in a fast dissolution of both syringyl and guaiacyl units. (d) The association of syringyl with guaiacyl units reduces the extent of condensation of guaiacyl units in protolignin,accelerating the dissolution of these guaiacyl units during pulping. (e) Syringyl units prevent further condensation of guaiacyl units through the formation of guaiacyl-syringyl type of diphenylmethane moieties.広葉樹クラフト脱リグニン過程における構成シリンギル単位の役割を明確にするため, Douglas-fir および Sweetgum のクラフト蒸解を行なった。パルプ残留リグニンの構造をリグニンを単離することなく定量的に解析し, パルプ化過程におけるリグニンの組成変化を両樹種間で比較検討した。クラフト蒸解における針葉樹および広葉樹間の最も重要な相違は, 縮合型単位の生成と溶出にあることが明らかとなった。シリンギル単位はリグニン分子にフレキシビリティーを与えること, また, シリンギルーグアイアシル型ジフェニルメタン縮合構造の形成を通して, グアイアシル単位の高度な縮合を阻止することが示された。
- Faculty of Bioresources, Mie Universityの論文
- 1991-01-31
Faculty of Bioresources, Mie University | 論文
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