Generation of xylose solutions from Eucalyptus globulus wood by autohydrolysis-posthydrolysis processes: posthydrolysis kinetics.
Eucalyptus wood samples were treated with water under selected operational conditions (autohydrolysis reaction) to obtain a liquid phase containing hemicellulose-decomposition products (mainly acetylated xylooligosaccharides, xylose and acetic acid). In a further acid-catalysed step (posthydrolysis reaction), xylooligosaccharides were converted into xylose, a carbon source for further fermentation. The kinetic pattern governing the posthydrolysis step was established by reacting xylooligosaccharide-containing liquors at 100.5 degrees C, 115 degrees C, 125 degrees C or 135 degrees C in media containing 0.5, 1.0, 1.5 or 2 wt% of catalyst (sulphuric acid). The time course of the concentrations of xylooligosaccharides, xylose, furfural and acetic acid were determined, and the results were interpreted by means of a kinetic model which allowed a close reproduction of the experimental data. Almost quantitative conversion of xylooligosaccharides into xylose was achieved under a variety of experimental conditions. The first-order, kinetic coefficient for xylooligosaccharide hydrolysis (k1, h(-1)) varied with both temperature (T, K) and molar sulphuric acid concentration (C) according to the equation In k1 = 36.66 + 1.00lnC - 108.0/(8.314T). The hydrolysis of acetyl groups followed a first-order kinetics. The corresponding kinetic coefficient (ka, h(-1) was correlated with the operational conditions by the equation Inka = 26.80+ 1.18 InC - 73.37/(8.314T).
Garrote
G
G
Chemical Engineering Department, University of Vigo, Edificio Politécnico, Ourense, Spain.
Domínguez
H
H
Parajó
J C
JC
D019342:Acetic Acid / Q000378:metabolism; D000107:Acetylation; D001089:Arabinose / Q000378:metabolism; D018533:Biomass; D001709:Biotechnology / Q000379:methods; D005052:Eucalyptus / Q000737:chemistry*; D005662:Furaldehyde / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006358:Hot Temperature; D006868:Hydrolysis; D007700:Kinetics; D008956:Models, Chemical; D012996:Solutions; D013464:Sulfuric Acids / Q000378:metabolism; D013816:Thermodynamics; D013997:Time Factors; D014867:Water / Q000378:metabolism; D014934:Wood; D014994:Xylose / Q000378:metabolism*
D012996:Solutions; D013464:Sulfuric Acids; D014867:Water; D014994:Xylose; D001089:Arabinose; D005662:Furaldehyde; D005947:Glucose; C033158:sulfuric acid; D019342:Acetic Acid