草类木素的氨化反应 Ⅱ.反应动力学和产物结构分析

Oxidative Ammonolysis of Lignin from Non-Wood Raw Materials Part2--Reaction Dynamics and Analysis of Reaction Products

木素的氨化反应可分为两个阶段 ,反应遵循准一级 (pseudo firstorder)方程 :ln[(N∞ -Nt) /N∞]=-kt;动力学研究表明 ,在 10 0℃条件下约有 2 .3%的N在刚达到预定温度的时间内结合进入麦草工业木素 (PTL) ,但预定温度为 130℃时 ,约有 3 .7%的N在同样时间内结合进入PTL分子。1H 13C2D NMRHMQC谱图可见木素分子的碎裂化现象十分明显。

Two stages of reaction were derived during oxidative ammonolysis of lignin from non-wood raw materials under condition of 100℃and 165 min, from 0 to 45 min was the first stage, from 45 to 165 min was the second. The reaction was in accordance with the pseudo first order equation: Ln[(N ∞-N t)/N ∞]=-kt; Results from dynamic studies indicated that about 2.3% of nitrogen was bound to the PTL molecule at the temperature of 100℃, but 3.7% at 130℃, the binding process is at an instantaneous velocity. 1 H - 13 C 2D NMR HMQC spectrometry presented that there was obvious fragmentation on the surface of lignin molecule, it was possible that superficial oxidative modification, such as formation of -CHO and -COOH from oxidation of -CH 3 at side chain of it, took place during process of ammonolysis. However, there was no evident changes in the inner parts of highly-condensed structure of PTL.