Structural Characteristics of Fast Growing Poplar Wood Lignin

快速生长的树木作为纸浆和纸板工业的原料越来越引起人们的兴趣，可以肯定的是，只有快速生长的树木才能满足未来世界范围内对木质原料的需求。充分收集速生树木的化学特性信息，对于开发这些材料的更好利用是非常重要的。本研究将讨论速生杨木木质素的结构特征，并与普通杨木木质素进行比较。两种杨树基本相同，生长在北海道东京大学森林，环境条件相似。前者是由新王子纸业公司开发的。这两棵树都是在1992年12月初砍倒的，在胸脯高度取得的木材样本用于鉴定。速生杨树的生长速度在树高和树径上都比普通杨树快1.5倍左右。虽然两种树木的木质素含量没有显著差异，但木质素的化学结构却存在显著差异。速生木木质素碱性硝基苯氧化产物中香兰素与丁香醛的摩尔比为2.0，远高于普通木木质素的1.5。高锰酸钾氧化，其他类型的木质素降解反应，也给出了一致的结果。这些结果表明，就非凝聚型结构单元而言，速生乔木木质素明显富含丁香基型结构。并比较了速生木木质素与普通木木质素在木质素大分子中的分子量分布和碳碳键的贡献。

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.