Dilute acid hydrolysis of paper birch: Kinetics studies of xylan and acetyl‐group hydrolysis

Abstract

Batch hydrolysis kinetics of paper birch (Betula papyrifera) xylan and its associated acetyl groups in dilute sulfuric acid have been measured for acid concentrations of between 0.04 and 0.18M and temperatures of between 100 and 170 degrees C. Only 5% of the cellulose was hydrolyzed for up to 85% xylan removal. Rate data were correlated well by a parallel reaction model based on the existence of reactive and resistant xylan portions. The resulting rate equation predicts the experimental xylan concentrations in the residue to within 10%. Hydrolysis of xylan-associated acetyl groups was found to occur at the same rate as that of xylan, except at 100 degrees C, where acetyl is released preferentially. No effect of acid concentration on the rate of acetyl removal relative to that of xylan was evident.

Hot Water Pretreatment of Boreal Aspen Woodchips in a Pilot Scale Digester

“…With the extended extraction time, monosaccharides are dehydrated to furfural and hydroxymethylfurfural (HMF). There are models describing hot water extraction as a homogeneous system with pseudo-first-order reactions and the extracted xylan having two different reactivities [5,[17][18][19]. Nabarlatz et al proposed a modified pseudo-first-order model that xylan is composed of xylose, arabinose, and acetic acid [20,21].…”

“…Liu proposed kinetic models for the extraction rate of sugars which were shown by Equations (19)- (29) with the assumption that condensation reactions are negligible, the breakage of glycosidic bonds has an equal rate, and the affinities of glycosidic bonds to hydrogen ions are the same. The overall extraction rate of sugars (s-xylo-oligomers) is given by: (19) where is the overall extraction rate of sugars; rs is the net reaction rate of s-oligomer (or oligosaccharides contain "s" units); kDX is the rate constant for the degradation of monomeric sugar; C1 is the mole concentration of monosaccharides in the liquor; N0 is the maximum length of oligosaccharides can be cleaved off and dissolved in the liquor; kE is the rate constant of dissolution for each extractable macromolecule; as is the specific surface area or m 2 -furface area of biomass per m 3 -liquor volume; P1 is the total units of xylose residues in the solid for xylan which has a degree of polymerization less than N0; DP0 is the average degree of polymerization for xylan in the solid which has a chain shorter than N0; Σθn is the total concentration of xylan on the biomass solid surface. Initially, the concentration of small xylan molecules on the solid surface is very low, which could be negligible.…”

Combined Bio‐carbonization and Dyeing of Wool: A Possibility Using Cell Wall‐Degrading Enzymes and 1:1 Metal–Complex Dyes

“…Analyzing the particular case of the dyeing with acid-leveling dyes (Dye C, using pH 3.0) a slight increase in glucose yield can also be observed when compared to the B, D, and E dyes. According to the acid hydrolysis mechanism for the pectic and lignocellulosic materials [25][26][27][28][29][30], the variation of the pH of the dyeing process, depending on the leveling properties of the dyes, showed a different range of degradation in the plant material, after wool dyeing. The relation between the pH used to perform the dyeing procedure and the degradation of the plant material evaluated by the RS yield seems quite evident.…”

“…However, the dependence of the leveling properties with pH is also important regarding the high performance and quality of the wool products. Also, according to the acid hydrolysis mechanism for the pectic and lignocellulosic materials, the lower the pH value used for the incubation the higher is the degradation of pectins, hemicelluloses, and cellulose, whenever all the other factors of the process are constant [25][26][27][28][29][30][31]. In accordance to this, the variation of the pH of the dyeing process, depending on the leveling properties of the dyes, should provide a different range of degradation in the plant material after wool dyeing.…”

Kinetic study of pentosan solubility during heating and reacting processes of steam treatment of green bamboo

“…The published models that delve into the solubility of hemicelluloses (mainly pentosan) can be divided into two categories: the homogeneous pseudo-first-order model (Aguilar et al, 2002;Saeman, 1945) and the biphasic reaction model that incorporates fast (easy) and slow (difficult) hydrolyzing fractions (Kobayashi and Sakai, 1956;Maloney et al, 1985;Zhao et al, 2012;Zhu et al, 2012a). Some deviations from both classic models have been proposed, and these models take into consideration the intermediates (Abatzoglou et al, 1992), the mass transfer effect (Brennan and Wyman, 2004;Mittal et al, 2009) or catalysts (Zhu et al, 2012a).…”