落叶松和水曲柳木质素热降解机理对比

Comparative studies of thermal degradation between larch lignin and manchurian ash lignin

用TGA,FTIR和XPS等手段对落叶松木质素和水曲柳木质素凝聚相的热降解过程及成炭行为进行对比研究。TGA分析表明:在高温纯氮条件下,落叶松木质素比水曲柳木质素剩余更多的炭残渣,这是由于落叶松木质素中的C-C键较多,使得落叶松木质素的碳骨架比水曲柳木质素的碳骨架更稳定。在空气气氛中,木质素在高温时完全分解为挥发性物质,这两种树的木质素均没有炭残余物,主要是由于在氧的催化作用下,C-C键和C-H键发生了氧化反应,这已经被FTIR实验证明。FTIR和XPS分析表明,在纯氮气气氛中,脂肪族酯键发生断裂,在凝聚态生成更多的苯环。根据C1s总强度和C1s(C-C)的相对强度以及碳/氧比例的显著提高得出,水曲柳木质素交联速度较大。

The thermal degradation and charring of both larch lignin and manchurian ash lignin in the condensed phase were comparatively investigated by using TGA, FTIR and XPS. TGA experimental results showed that larch lignin produced more char residue than manchurian ash lignin under pure nitrogen at high temperature. This demonstrated that the carbon backbone of larch lignin was more than that of manchurian ash lignin. This is attributed to more carbon - carbon bonds existing in larch lignin than in manchurian ash lignin. Under air condition, the lignin completely was decomposed to form volatiles at high temperature. There was no char remained in both larch lignin and manchurian ash lignin. This was because oxygen catalyzed the oxidative reactions of bonds, which supported by FTIR.FTIR and XPS data indicated that the cleavage of aliphatic ester bonds took place mainly under pure nitrogen, and more aromatic rings remained in the condensed phase. Manhurian ash lignin showed a high crosslinking rate based upon the relative intensity of Cls and Cls（ C - C） and an obvious increase of the ratio of carbon to oxygen. Different thermal degradation of both larch lignin and manchurian ash lignin under pure nitrogen and air has been proved by TGA, FTIR and XPS.