Fractionation of depectinated sugar beet pulp into cellulose, hemicellulose, and lignin with NaOH/urea/H₂O and ionic liquid

This study proposes a novel and feasible dissolution and fractionation method of depectinated sugar beet pulp (SBP) in NaOH/Urea/H₂O, ionic liquid (IL) and alkaline treatment processes. Interestingly, the complicated structure of SBP can be treated with 30 % H₂SO₄ to increase the dissolution rate. Scanning electron microscope (SEM) analysis confirmed that the appearance of cellulose and hemicellulose obtained by two methods were different. At the same time, two lignin fractions showed irregular high-density clusters, which were composed of a large number of submicron particles. The crystal structure of two cellulose fractions changed from cellulose I to cellulose II. The thermal stability of cellulose and lignin obtained by ionic liquid was slightly better than that obtained by NaOH/urea/H₂O. Results of Fourier transform infrared (FTIR) and ¹³C NMR showed that the chemical structures of SBP cellulose, hemicellulose and lignin regenerated from NaOH/urea/H₂O and ionic liquid were similar.