Fractional separation of cellulose from eucalyptus wood through ternary solvents and simplified bleaching treatment.

In the present study, cellulose was effectively separated from eucalyptus wood with ternary solvents containing organic base 1,1,3,3-tetramethyl guanidine and other organic solvents such as morpholine, N-ethyl morpholine, dimethyl formamide, glycerin, ethylene glycol and diethylene glycol. It was found that the combination of 1,1,3,3-tetramethyl guanidine with morpholine was favorable for achieving high delignification and less loss of cellulose. The removal of lignin and hemicellulose achieved 89.8% and 81.4% after heating for 6 h at 160 °C, respectively. It was found that the combination of 1,1,3,3-tetramethyl guanidine with morpholine was favorable for achieving high delignification and less loss of cellulose. The removal of lignin and hemicellulose achieved 89.8% and 81.4% after heating for 6 h at 160 °C, respectively. The addition of morpholine and water promoted the dissolution of lignin and reduced the degradation of cellulose. Subsequently, the crude cellulose was further purified through a simplified bleaching process, the final removal of lignin and hemicellulose increased to 98.7% and 97.5% respectively, and cellulose with a purity of 96.9% was achieved. The scanning electron microscopy analysis indicated that the diameter of cellulose bundles decreased from about 250 μm to about 20 μm after organic solvents treatment. The fiber bundle was completely separated into a single fiber with a diameter of about 5–10 μm after bleaching process. X-ray diffraction analysis revealed an increase in the crystallinity of fiber from 69.4% to 83.3%, implying a reduction of lignin and hemicellulose in eucalyptus. Fourier transform infrared spectra revealed the high selective removal of lignin and hemicellulose. Two-dimensional ¹H-¹³C Heteronuclear singular quantum correlation was performed to investigated the structure units and linkages of lignin and found that only the structural signal of C₅-H₅ in guaiacyl (G₅) alone existed in the aromatic region, while the signals -OCH₃, C_γ–H_γ in β-O-4' (A_γ) and β-β' (C_γ) remained in the side chain region, indicating that lignin could be effectively degraded and dissolved by the ternary solvents. In conclusion, high purity cellulose was obtained from eucalyptus wood by environmentally friendly and recyclable processes. [ABSTRACT FROM AUTHOR]