乙醇木素纯化及其结构表征

Purification of Ethanol-organosolv Lignin and Characterization of Its Structure

关键词:  乙醇制浆  木素  提纯  结构分析

Key Words:ethanol-organosolv pulping  lignin  purification  structure analysis

摘要:采用弱酸法及液液提纯法提纯杨木乙醇制浆黑液中分离的木素，通过离子色谱仪、红外光谱仪、碳核磁共振光谱仪及热重分析仪，分析纯化效果并对纯化后木素的结构及其热稳定性进行分析。结果表明，粗木素总含糖量为0.99%，木素纯度为98.67%；液液法纯化对糖类杂质的去除效果较好，纯化后总糖含量降低到0.36%，木素纯度提高至99.64%。液液法纯化后木素的热稳定性有一定的提高，最大失重峰由320℃提高至350℃。纯化前后乙醇木素结构有一定变化，木素缩合程度有一定的增加。纯化后乙醇木素富含游离羟基、甲氧基等功能基，更加有利于其利用。纯化后乙醇木素纯度较高有利于结构分析。

Abstract:Lignin exiting in the black liquor of aspen ethanol-organosolv pulping was purified by the methods of mild acid hydrolysis and liquid-liquid extraction. The properties of purified lignin, including chemical structure and thermal stability, were analyzed by ion chromatography, FT-IR, 13C-NMR and thermogravimetric analysis. Results showed that the method of liquid-liquid extraction was better than mild acid hydrolysis in terms of removing carbohydrates. The content of total sugar in crude lignin was 0.99% and the purity of lignin was 98.67%. After purification, the content of total sugar in lignin was decreased to 0.36% and the purity of lignin was increased to 99.64%. It was found that the thermal stability of purified lignin was better than crude lignin indicated by the fact that the maximum weight loss peak of lignin shifted from 320℃ to 350℃. However, the structure of lignin had little change after purification. The purified aspen ethanol-organosolv lignin was rich in functional groups such as hydroxyl groups, methoxy groups, which was more benefite to its utilization. The higher purity of lignin was beneficial for analyzing the structure of the ethanol-organosolv lignin.