草类木素的氨化反应——反应动力学和产物结构分析

Oxidative Ammonolysis of Lignin from Non-Wood Fibers Ⅱ. Reaction Dynamics and Analysis of Products from Reaction

木素的氨化反应可分为两个阶段 ,0— 4 5min为第一反应阶段 ,4 5— 165min为第二反应阶段 ,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 %左右的N在刚达到预定温度的时间内结合进入PTL ,但预定温度为 130℃时 ,约有 3 .7%左右的N在同样的时间内结合进入PTL分子 ,这是一种瞬时反应历程。1 H—1 3 C2D—NMRHMQC谱图可见木素分子的碎裂化现象十分明显 ,很可能在氧化性氨化反应过程中 ,木素大分子表面基团发生了氧化性修饰 ,如一些侧链的—CH3 的氧化反应形成—CHO和—COOH ,然后与N结合等 。

Two stages of reaction were observed during the process of oxidative ammonolysis of lignin from non-wood fibers under condition of 100℃ and 165min, first was from 0 to 45 min, second was from 45 to 165 min. 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 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.