Structural Characteristics of Fast Growing Poplar Wood Lignin

速生树种作为纸浆和纸板工业的原料越来越受到人们的关注，只有速生树种才能满足未来世界范围内对木质原料的需求。为了更好地开发利用速生树种的资源，充分了解速生树种的化学特性是非常重要的，本研究将速生杨木木质素与普通白杨木质素进行比较，探讨速生杨木木质素的结构特征。这两种白杨木材基本上是相同的物种，生长在东京大学森林，北海道在类似的环境条件。前者是由新王子制纸公司开发的，这两棵树都是在1992年12月初砍伐的，并在胸高处获得的木材样品用于表征。速生白杨树高和胸径的生长速度比普通杨快1.5倍左右。虽然这两种树种的木质素含量没有明显差异，但木质素的化学结构却存在明显差异。速生树种木质素碱性硝基苯氧化产物中香草醛与乙醛的摩尔比为2.0，远高于普通木材木质素的1.5。高锰酸钾氧化反应和其它类型的木质素降解反应也得到了一致的结果。这些结果表明，就非缩合型结构单元而言，速生木木质素中明显富含双辛烯基型结构。并与普通木材木质素进行了比较，分析了速生木木质素分子量分布和碳-碳键对木质素大分子的贡献。

Fast-growing trees have been attracting an increased interest as the raw materials for pulp and board industries, and it is quite sure that only fast-growing trees can fulfilll the world-wide demand of woody raw materials in future. To collect full information of the chemical characteristics of fast-growing trees seems to be very important to develop the better utilization of those materials.In this research, structural characteristics of fast-growing poplar wood lignin will be discussed in comparison with normal poplar wood lignin. Both poplar woods were basically same species and grown in the Tokyo University Forest, Hokkaido under similar environmental conditions. The former is the one which was developed by New Oji Paper Company.Both trees were felled at the beginning of December, 1992, and the wood samples obtained at the breast height were used for the characterization. The growing rate of the fast-growing poplar was about 1.5 times faster than that of normal one in terms of the height and diameter of those trees. Although those trees didn't show any noticeable difference in lignin content, remarkable differences were found in the chemical structures of lignins in those two trees. Vanillin to syringaldehyde molar ratio in the alkaline nitrobenzene oxidation products of fast-growing tree lignin was 2.0, which was much higher than that of normal wood lignin, 1.5. Potassium permanganate oxidation, other type of lignin degradation reaction, also gave the consistent results. These results suggest that as far as the non-condensed type structural units concerned, lignin in fast-growing tree is apparently rich in syringyl type structures. Molecular weight distribution and contribution of carbon-carbon bonds in lignin macromolecule of fast-growing tree lignin were also evaluated in comparison with those of normal wood lignin.