Kinetic Modeling of the Autohydrolysis of Lignocellulosic Biomass for the Production of Hemicellulose-Derived Oligosaccharides

Abstract

Xylose-based oligosaccharides produced from xylan-rich hemicelluloses (xylo-oligomers) are carbohydrates with potential food and pharmaceutical uses. Autohydrolysis of lignocellulosic biomass is an efficient way to produce xylo-oligomers in a reasonable yield and a wide variety of compositions (anhydroarabinose/anhydroxylose and acetyl/anhydroxylose mass ratios). In this work, we develop a kinetic model for the autohydrolysis of xylan in lignocellulosic biomass that describes the yields of the different reaction products and explains the changes in the chemical composition of the xylo-oligomers due to reaction temperature and time. This model assumes that xylan is made up of three monomers (xylose, arabinose, and acetic acid) and that there are two xylan fractions with different compositions and reactivities toward hydrolysis. Both fractions are hydrolyzed to xylo-oligomers, which are hydrolyzed to xylose, arabinose, and acetic acid. Finally, monosaccharides dehydrate to furfural and degradation products. The model is validated with experimental data obtained for the autohydrolysis of corncobs in a batch reactor system at temperatures from 150 to 190 °C. The amount and composition of each xylan fraction, as well as the activation energies and frequency factors for all the reactions, are calculated from the experimental data. This model provides a satisfactory interpretation of the experimental data.