多种预处理方法对纤维素结晶结构的影响

分别采用丙三醇、NaOH、乙二胺(EDA)、H₃PO₄以及离子液体[BMIM]Cl对不同来源的纤维素进行预处理,通过X射线衍射(XRD)、固体核磁共振(CP/MAS ¹³C NMR)及傅里叶变换红外光谱(FT-IR)研究了这几种预处理方法对纤维素结晶结构的影响。结果表明,16. 5 wt%的NaOH及60 wt%的H₃PO₄预处理可将天然纤维素结构从Ⅰ型转化为Ⅱ型,EDA预处理可将天然纤维素结构转化为Ⅲ型,85 wt%的H₃PO₄以及离子液体[BMIM]Cl预处理可将纤维素转化为无定形结构。[BMIM]Cl预处理比85 wt%的H₃PO₄预处理更有利于无定形纤维素的产生。结构转化过程中,纤维素的羟甲基构象相应地发生变化。结晶度方面,低质量分数NaOH预处理有利于获得低结晶度的纤维素,EDA预处理对纤维素结晶度的影响与原料结构关系较小,而NaOH与离子液体[BMIM]Cl预处理对纤维素结晶度的...

The Effects of Various Pretreatment Methods on Cellulose Crystalline Structure

In this paper,cellulose samples including Avicel,α-cellulose,and cotton fibers were subjected to the pretreatments of glycerol,sodium hydroxide,ethylenediamine,phosphoric acid and ionic liquid,respectively. The effects of the different pretreatments on cellulose crystalline structure were investigated. According to the XRD,CP/MAS 13C NMR and FT-IR analysis results,the 16. 5 wt% NaOH and the 60 wt% H3PO4 pretreatment could convert natural cellulose from Ⅰ to Ⅱ allomorph,while the EDA pretreatment could convert natural cellulose to Ⅲ allomorph. Additionly,the 85 wt% H3PO4 and the[BMIM]Cl pretreatments could convert natural cellulose to amorphous cellulose.However,the[BMIM]Cl pretreatment was beneficial to produce amorphous cellulose compared to the 85 wt% H3PO4 pretreatment. During all the conversion process,the hydroxymethyl conformation of cellulose samples changed accordingly. Besides,there was no significant relationship between the effect of EDA pretreatment on cellulose crystallinity and its source of raw materials. However,the effects of NaOH and[BMIM]Cl pretreatments on the crystallinity of cellulose were related to the resouce of the cellulose. The higher the crystallinity of the raw materials was,the higher crystallinity of the cellulose after pretreatment.