有机溶剂法麦草木质素的化学特性研究

用不同浓度的乙酸-水、甲酸-乙酸-水、甲醇-水及乙醇-水溶液处理脱蜡的麦草,获得的木质素采用FT-IR、~1H-NMR、~(13)C-NMR及化学法研究其化学特性,结果表明,有机酸溶液比有机醇溶液脱木素作用更加广泛,能选择性降解麦草中的纤维素、木质素及半纤维素。甲酸对木质素的溶解有显著影响。随着乙酸或甲酸浓度的增加,愈创木基结构单元增加,木质素缩合。有机醇处理获得的木质素中,含有几乎等量的非缩合型愈创木基和紫丁香基结构单元及少量的对羟苯基结构单元。

Chemical Characteristic of Organosolv Lignins from Wheat Straw

Dewaxed wheat straw was treated with different concentration of acetic acid-H_2O,formic acid-acetic acid-H_2O,methanol-H_2O and ethanol-H_2O using 0.1% HCl as a catalyst.Lignins were characterized by FT-IR,~1H-NMR and ~(13)C NMR spectroscopy and by their content of hemicelluloses,composition of phenolic acids and aldehydes,molecular weight,thermal stability.The results indicated that aqueous or- ganic acid is more effective than aqueous organic alcohol for extensive delignification and selective fractionation of cellulose,lignin and hemi- celluloses from the straw.In particular,the addition of formic acid has a significant effect on the dissolution of lignin.An increase in concen- tration of acetic acid or formic acid in organosolv results in an increment of guaiacyl units and hgnin condensation.However,the lignin re- leased during the treatment with aqueous organic alcohol without organic acid contains almost equal amounts of non-condensed guaiacyl and syringyl units with fewer p-hydroxyphenyl units.