水热预水解分离相思木半纤维素及其组分与结构分析

通过水热预水解法处理相思木制得预水解液,采用乙醇沉淀回收预水解液中的半纤维素,通过条件实验优化了最佳回收半纤维素的预水解条件,然后对回收的半纤维素进行热稳定性、成分和结构分析。结果发现,获得最大半纤维素回收率的预水解条件为170℃/20min,原料中碳水化合物回收率为3.93%,回收的半纤维素中木糖为主要成分占75.56%,葡萄糖占10.71%,半乳糖占7.80%。离子色谱分析表明160℃/40min,170℃/15min、170℃/25min和180℃/15min水解条件下的回收半纤维素组分与170℃/20min时的回收半纤维素化学组分相同,但含量上略有差别;热重分析表明水解温度提高和时间延长使回收半纤维素热稳定性降低;核磁共振和红外光谱分析结果表明回收半纤维素的聚木糖主链上残留有乙酰基、阿拉伯糖和半乳糖连接。

Isolation of hemicelluloses from acacia wood with hydrothermal prehydrolysis and its characterization of structure and component

Hydrothermal prehydrolysis of acacia wood was conducted at various conditions and the hemicelluloses dissolved in prehydrolysate was recovered by ethanol precipitation. Conditions test design was used to optimize the pre-hydrolysis conditions for the maximum hemicelluloses recovery rate as solid phase. Then, the composition, thermal stability and structural characterization were analyzed on the recovered hemicelluloses. The optimum pre-hydrolysis temperature and time were determined to be 170℃ and 20 min, respectively. Recovery rate of 3.93% against carbohydrate content of wood chip was obtained under the optimum conditions and main composition was xylose, accounting for 75.56% in mass, and 10.71% of glucose and 7.80% of galactose were also found. The recovered hemicelluloses at 160℃/40 min, 170℃/15 min,170℃/25 min and 180℃/15 min showed a same composition with the result of 170℃/20 min but a little bit difference in the content by the analysis of ion chromatography. The thermo gravimetric analysis indicated that thermal stability of recovered hemicelluloses decreased along with the improvement of prehydrolysis temperature and extension of prehydrolysis time. Linkage of acetyl group, arabinose and galactose was found on the xylan chain by the analysis of nuclear magnetic resonance and Fourier transform infrared spectroscopy.