有机-无机溶剂连续抽提巨龙竹木质素及其结构表征

为了分析巨龙竹木质素的结构特征,采用有机-无机溶剂连续抽提的方式将木质素和半纤维素进行分离,脱蜡竹粉依次用80%二氧六环、80%二氧六环-0.5% NaOH、2% NaOH、5% NaOH和8% NaOH连续抽提后,得5个木质素样品L₁~L₅,计算了木质素得率,并对抽提所得的木质素样品进行了红外光谱(FT-IR)、紫外光谱(UV)、核磁共振碳谱(¹³C NMR)和二维核磁共振(2D HSQC)分析。结果表明:在二氧六环和不同浓度碱性水溶液的连续抽提下,最终从巨龙竹原料中分离得到70.6%的原本木质素,其中木质素样品L₂的纯度最高,表明该方法是一种较为有效的竹材木质素组分分离方法。木质素的苯环骨架结构在分离过程中没有被破坏,但碱浓度的增加导致木质素中部分酯键发生断裂。巨龙竹木质素大分子主要由愈创木基单元(G)、紫丁香基单元(S)、对羟基苯基单元(H)组成,木质素大分子基本单元之间的联接键主要是β-O-4'醚键,除此之外还有β-β'、β-5'和β-1'联接。

Characterization of Lignin Fractions Isolated from Dendrocalamus sinicus with Organic-inorganic Sequential Extraction

In order to analyze the structural characteristics of lignin of Dendrocalamus sinicus Chia et J. L. Sun,the lignin and hemicelluloses were isolated by organic-inorganic sequential extraction.Dewaxing bamboo powder was sequentially extracted with 80% dioxane,80% dioxane-0.5% NaOH,2% NaOH aqueous,5% NaOH and 8% NaOH,respectively.Five lignin samples(L₁-L₅) were obtained,and the yields of lignin were caculated.The structural features of the isolated bamboo lignin fractions were characterized by FT-IR,UV,¹³C NMR and 2D HSQC.The analysis results indicated that 70.6% original lignin was fractionated from D. sinicus after five-step treatments,and the highest purity lignin sample was L₂.This indicated this method was an effective method to isolate lignin.The structure of lignin was saved during the separation process,but a part of ester linkages were broken due to the alkaline surroundings.In addition,the lignin polymer isolated from D. sinicus consisted of guaiacyl,syringyl and p-hydroxyphenyl units.The inter-units linkages presented in the bamboo lignin including β-O-4' linkages, β-β' linkages, β-5' and β-1' linkages.