Structural features and thermal characterization of bagasse hemicelluloses obtained from the yellow liquor of active oxygen cooking process

The bagasse hemicelluloses from the yellow liquor of active oxygen cooking process were successively precipitated by ethanol. The chemical component and structure of five hemicellulosic fractions and final residue were elucidated by a combination of destructive and nondestructive methods. Results showed that xylose was the main sugar residue in the hemicellulosic fractions, whereas final residue contained high content of uronic acids (30.47%), and lignin. The hemicellulosic fractions were composed of (1 → 4)-linked-β-d-xylopyranosyl backbones, but the degree of branching of hemicelluloses fractions depended on the precipitation process. Only 1.84% of hemicelluloses in the yellow liquor showed high molecular weight (24,078 g/mol), the remainder of hemicellulosic fractions was significantly degraded under cooking conditions. In addition, some branched sugar residues fell off the backbone and dissolved in the yellow liquor during the cooking process. And the thermal stability may relate to the ash content, component, molecular weight, and degree of branching of hemicellulosic fraction.