Refining of autohydrolysis liquors for manufacturing xylooligosaccharides: evaluation of operational strategies.

When xylan-containing lignocellulosic materials are subjected to the action of heat in an aqueous medium (autohydrolysis reaction) under suitable operational conditions, the heterocyclic ether bonds of the polymeric chain are split to give xylooligosaccharides (XO) and a variety of other products derived from hemicelluloses, lignin and extractives. For product applications requiring high-purity XO, subsequent purification stages have to be implemented. Various strategies have been evaluated for refining Eucalyptus wood autohydrolysis liquors, including the two-stage reaction, precipitation and solvent extraction of freeze-dried, dewaxed liquors. Data on the degree of xylooligosaccharide recovery as well as on the composition of the isolates (measured in terms of hemicellulose-derived products and non-saccharide products) are provided for the various operational procedures assayed.