有机酸水溶液提取玉米芯木质素及其性质研究

Extraction and Characterization of Lignin from Corncob by Organic Acid Aqueous Solutions

摘要:

以甲酸/乙酸水溶液为溶剂提取玉米芯木质素。利用响应面法考察了甲酸浓度、提取温度和反应时间等因素对木质素产率的影响。结果表明，最优的反应条件为：V (甲酸)∶V(乙酸) =4∶5，提取温度为91 ℃，反应时间4 h，在该条件下木质素产率的预测值为67.91 %，实验验证值为70.16 %。利用紫外光谱法和化学滴定法研究了木质素的纯度、酚羟基和羧基含量，测定了木质素在不同溶剂中的溶解性，通过红外、紫外、核磁共振及热重等方法对所提取的木质素的结构和性质进行了表征。结果显示，有机酸水溶液提取的木质素同时含有紫丁香单元（S）、愈创木基单元（G）和对羟基苯丙烷单元（H），而且与碱木质素结构相似。热重分析表明，该木质素具有更好的热稳定性，600 ℃时热解残余物的比例为42 %。有机酸水溶液处理法是提取高纯度玉米芯木质素的有效方法。

Abstract:

Corncob lignin was extracted with formic acid /acetic acid aqueous solution. The Response Surface Methodology (RSM) analysis was used to study the effects of process parameters on the lignin yield and the optimized condition (formic acid/acetic acid ratio of 4/5(V/V), 91 ℃ and 4 h) was established. The highest yield of lignin was predicted to be 67.91 % by the RSM model and revised to be 70.16 % by the experiments. The purity of obtained lignin, the contents of phenolic hydroxyl and carboxyl group were determined using differential UV-Spectroscopy method ( method) and chemical titration. The complex structures of the obtained lignin were further characterized by FTIR, UV, TG, 1HNMR and compared with that extracted with alkali. The results showed that the lignin is composed of guaiacyl unit (G), syringyl unit (S) and p-hydroxyphenyl unitl (H) and is quite similar with the alkali one in structure. The thermogravimetric analysis showed that the lignin extracted with organic acid queous solution is thermally more stabile than the alkali one and the char residues at 600 ℃ was 42 %. Extraction of lignin from corncob with organic acid aqueous solution was proved to be an efficient method.