Research on the degradation behaviors of wood pulp cellulose in ionic liquids

Abstract

Utilizing phosphate-based ionic liquids (ILs) solvents for dissolving cellulose to prepare cellulose fibers has attracted much attention for its convenience, high yield, stability and sustainability. However, the degradation behavior during dissolving of cellulose in ILs, which is an important factor for fabricating cellulose fiber, is still unclear. In this work, the degradation of wood pulped cellulose (WPC) in three kinds of phosphate-based ILs: 1-ethyl-3-methylimidazolium dimethyl phosphate ([Emim]DMP), 1-ethyl-3-methylimidazolium diethyl phosphate ([Emim]DEP) and 1-butyl-3-ethylimidazolium diethyl phosphate ([Beim]DEP), were systematically investigated at different dissolution temperatures and dissolution times. The results indicated that the degradation degree of WPC in three ILs follows the order of [Emim]DEP > [Beim]DEP > [Emim]DMP, which is consistent with interaction results obtained by quantum chemical calculation, and degradation degree increases follows the rising of dissolution temperature and the accumulation of dissolution time. Moreover, no reducing sugar (RS) was found in any recycled ILs even when the degree of polymerization (DP) of regenerated cellulose (RC) decreased by 30.4%. In addition, according to the Fourier transform infrared and X-ray diffraction data, the results further proved that the crystallization type of RC changed from type Ⅰ to type Ⅱ. Here, preferable dissolving parameters and experiments data of multiple conditions are provided, which may provide practical reference and guidance for both scientific research and industrial.