Efficient separation of functional xylooligosaccharide, cellulose and lignin from poplar via thermal acetic acid/sodium acetate hydrolysis and subsequent kraft pulping

Thermal acetic acid/sodium acetate hydrolysis (ASH) on poplar wood chips were carried out to obtain functional xylooligosaccharide, then the hydrolyzed wood chips were subjected to kraft pulping (KP) to fractionate cellulose and lignin. The separated three fractions were extensively characterized for further utilization in view of the integral biorefinery concept. The extraction efficiency of hemicelluloses by ASH strongly depends on the buffer ratio of the acetic acid/sodium acetate buffer solution. The ASH facilitated producing a high ratio of xylooligosaccharides with high molecular weight, while prevented further degradation of the saccharides, and simultaneously inhibited the condensation of lignin facilitating the subsequent kraft delignification. The obtained cellulose pulps had higher intrinsic viscosities as compared with the traditional autohydrolysis-KP process. Moreover, the ASH-KP process delivered a high purity of lignin with relatively high molecular weight. Therefore, the proposed integrated fractionation strategy is conducive to convert the lignocellulosic components into bio-based functional materials.