乙酸强化水热预水解对相思木半纤维素溶出及组分与结构的影响

Effects of Acetic Acid-strengthened Hydrothermal Prehydrolysis on the Dissolution of Hemicelluloses from Acacia Wood and the Component and Structure of the Hemicelluloses

中文关键词:  生物质  水解  半纤维素  回收  水热

Key Words:biomass  hydrolysis  hemicelluloses  recovery  hydrothermal

中文摘要:

      在170℃下，分别采用水热预水解法和1.0%（质量分数）乙酸强化水热预水解法抽提相思木，通过乙醇沉淀法回收预水解液中的半纤维素，分析了乙酸对预水解液中溶解半纤维素的化学组分及含量、乙醇沉淀半纤维素回收率及其组分和结构的影响。结果表明，乙酸可显著提高预水解液中低聚糖和总糖含量；在170℃下预处理35 min时，乙醇沉淀半纤维素回收率最大；离子色谱和紫外光谱分析结果表明，乙酸强化水热预水解乙醇沉淀半纤维素的化学组分与水热预水解乙醇沉淀半纤维素相同，但木糖和木素含量较高，而阿拉伯糖和半乳糖含量偏低；凝胶色谱分析结果表明，乙酸强化水热预水解乙醇沉淀半纤维素平均分子质量低于水热预水解乙醇沉淀半纤维素；核磁共振分析结果表明，乙酸强化水热预水解乙醇沉淀半纤维素聚木糖主链上残留阿拉伯糖支链较少，有明显木素 碳水化合物复合体（LCC）存在。

Abstract:

      Hydrothermal prehydrolysis and 1.0%(w/w) acetic acid-strengthened hydrothermal prehydrolysis were conducted at 170℃ for the extraction of acacia wood and the dissolved hemicelluloses were recovered by ethanol precipitation. The effects of acetic acid on the composition, content and recovery rate of dissolved hemicelluloses in prehydrolysate, and the composition, molecular weight and structure of recovered hemicelluloses were investigated. Acetic acid could obviously increase the content of oligosaccharide and total saccharides in the prehydrolysate. The optimum prehydrolysis conditions for recovery of dissolved hemicelluloses were at 170℃ for 35 min. The ion chromatography analysis indicated that at the same condition the composition of hemicelluloses recovered from acetic aced hydrothermal prehydrolysate was the same with that from hydrothermal prehydrolysate, but the proportions of xylose and lignin were a little bit higher and proportions of arabinose and galactose were relatively lower. Much lower average molecular weight was found in the hemicelluloses recovered from acetic acid hydrothermal prehydrolysate by the test of gel chromatography. The nuclear magnetic resonance analysis indicated that the obvious presence of LCC structure and much fewer linkage of arabinose were found on the xylan chain of hemicellulose recovered from acetic acid hydrothermal prehydrolysate.