広葉樹材の200 °C飽和水蒸気熱処理によるセルロースの構造変化 - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Mokuzai gakkai shi Année : 2019

Changes in Crystal Structure of Cellulose in Hardwood Cell Walls by Hydrothermal Treatment at 200 °C under 1.6 Mpa

広葉樹材の200 °C飽和水蒸気熱処理によるセルロースの構造変化

Résumé

Air-dried samples of 20 hardwood species were saturated with water and subjected to thermal treatment in an autoclave at 200 °C for 2 hours under a saturated vapor pressure (1.6 MPa). Gelatinous layers were observed under optical microscope for and samples, which were considered to be tension wood. The other 18 samples contained no reaction wood. Structural changes of cellulose in the cell walls by the hydrothermal treatment were studied by X-ray diffraction. The diffraction peaks of 1 1 0 and 1 1 0 became closer to each other in every sample, and in many cases, merged to a single, relatively sharp peak. These phenomena suggest a change of cellulose crystalline structure from a monoclinic to a pseudo-orthorhombic system. The crystalline size calculated from the diffraction peak of 2 0 0 increased in all samples by the treatment that also induces hemicellulose leaching. Thus, the structural changes upon hydrothermal treatment are considered as a common reaction in hardwood. This phenomenon could be explained as co-crystallization of adjacent microfibrils. The -spacing of 2 0 0 decreased by 0.8-1.6% after annealing in 17 species, while that of decreased by only 0.5%, and those of and did not change by this treatment. In these 3 samples, the -spacings of 2 0 0 were originally smaller and the crystal sizes were larger than in the other 17 samples. The proportion of peak area due to the crystalline C4 in the solid-state 13 C CP/MAS NMR spectra suggested that the content of crystalline cellulose was higher in these 3 samples than in the other 17 samples.
20種の広葉樹気乾材を飽水状態にし,200 °C,2時間の水熱処理による構造変化を X 線回折により調べた。光学顕微鏡観察でハリギリ,エノキ試料は,あて材の特徴を示したが,他18試料は正常材であった。水熱処理後は全ての試料で1 1 0と1 1 0の回折が接近し,多くの場合で擬直方晶への変化がみられ,X 線結晶サイズ(2 0 0)は著しく増大した。これらの変化はヘミセルロースの溶出を伴う隣り合うミクロフィブリルの共結晶化によるものと考えられる。17樹種の試料では,水熱処理により2 0 0の面間隔が0.8−1.6% 減少したが,ハリギリでは0.5% 減少し,カキノキ,エノキでは殆ど変化しなかった。これら3試料は,他の17試料に比べ未処理での2 0 0の面間隔が小さく,結晶サイズが大きかった。さらに固体 13 C NMR による結晶性セルロース含有量は他試料より高かった。
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Dates et versions

hal-02951161 , version 1 (13-11-2020)

Identifiants

  • HAL Id : hal-02951161 , version 1

Citer

Yoshiharu Nishiyama, Yu Ogawa, Tomoko Kuribayashi, Yuji Matsumoto. 広葉樹材の200 °C飽和水蒸気熱処理によるセルロースの構造変化. Mokuzai gakkai shi, 2019. ⟨hal-02951161⟩
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