Autohydrolysis of corncob:: study of non-isothermal operation for xylooligosaccharide production

Corncob samples were treated with water (autohydrolysis reaction) under non-isothermal conditions (reaction temperature up to 216 degreesC) using a liquid to solid ratio of 8:1 kg/kg. The experimental variables considered were solid residue yield, solid residue composition (defined by the contents of cellulose, xylan, araban, acetyl groups and lignin in the solid residues) and composition of liquors (characterised by the concentrations of xylooligomers, xylose, glucose, arabinose, acetic acid and furfural). Most of the cellulose was retained in the solid phase, whereas partial delignification (up to 26% lignin removal) was achieved. Up to 94% of xylan was removed, producing xylooligomers (useful as food additives) and other reaction byproducts (including xylose and furfural). The decomposition of xylan into xylooligomers, with further generation of xylose, furfural and degradation products, was modelled by a series of parallel and consecutive reactions, which were assumed to be first order with coefficients showing an Arrhenius-type dependence on temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.