桉木预处理后固形物及提取液的特性

Characterization of eucalyptus wood residue and extraction liquor after pretreatment

在不同条件下对桉木片进行碱预处理和高温水预水解,研究了其对木片残渣及提取液的影响.在高温水预水解后,木片中的聚戊糖含量随温度的升高或时间的延长而降低,这是预处理后木片失重的主要原因.凝胶渗透色谱(GPC)分析结果显示,碱预处理后木片及提取液中半纤维素的数均分子量降低,且温度越高降低越明显.与碱预处理相比,高温水预水解后木片中半纤维素的分子量大幅度降低,但多分散性仍与原料木片相近.采用酶解-温和酸水解的方法制备木素(EMAL),水预水解后木片与原料木片相比,木素的平均分子量增加,而多分散系数略有降低.木素的31P-NMR定量分析结果表明,经高温水预水解后,总酚羟基含量几乎增加一倍,S/G有所增加,但脂肪族羟基与羧基含量则大大降低.

Hot water and alkaline pretreatment was done on eucalyptus chips under different conditions .The impact on prehydrolysate and wood residue is investigated .For autohydrolysis ,higher decrease of pentosan content in wood is shown with elevated temperature and extended reaction time ,which mainly contribute for the weight loss during pretreatment .Based on the GPC（Gel Permeation Chromatography） results ,the numberaverage molecular weight of hemicelluloses in alkaline extraction liquor and wood residues decreases ,which is greater for higher temperature .Compared with alkaline pretreatment ,hemicelluloses in autohydrolyzed chips has much lower molecular weight ,with similar dispersity to that in original wood .In the case of EMAL （Enzymatic/Acidolysis Lignin） lignin ,after autohydrolysis ,the average molecular weight is increased while the polydispersity shows a little decrease compared to that from original wood .Based on the quantitative 31 PNMR analysis ,after autohydrolysis ,the total phenolic hydroxyl groups almost doubled with higher S/G ratio ,but the amount of aliphatic hydroxyl and carboxyl groups shows great decrease .