Esterification process of hemicellulose and cellulose in kraft pulp (KP) was investigated. To identify the positions at which the hydroxyl groups of polysaccharides were esterified, heteronuclear single quantum coherence-nuclear magnetic resonance (HSQC-NMR) spectroscopy was used. The HSQC-NMR spectra of acetylated willow (Salix schwerinii E. L. Wolf) KP indicated only xylan was acetylated in the initial stages of the reaction, then xylan and surface of the cellulose crystals was modified in the next stage. After that, acetylation of the inner crystal region of the cellulose began before the completion of the xylan modification. To improve the reactivity of xylan in KP, the effect of drying or dehydration of never-dried KP before acetylation was investigated. It was suggested that the cellulose‒cellulose and/or cellulose‒hemicellulose adhesion was formed during drying or dehydration process, resulting in reduction of reactivity of the xylan.
