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In this study, experimental viscosity results of hardwood prehydrolysis liquor (PHL) from the kraft-based dissolving pulp production process were obtained and used to develop empirical models describing the effect of temperature, solid content, the interaction between solute and solvent, and the concentration of lignin and hemicelluloses. The concentration, molar mass, and molecular weight of lignin and polysaccharide of PHL, all are the factors that affect the rheological behavior of the PHL. The results showed that, on the one side, Zaman and Fricke’s model gave better fitting when the viscosity is lower, on the other hand, a much better fitting of the Moosavifar’s model could be obtained by taking interaction between solute and solvent, solids content, concentration of lignin and hemicelluloses into account when the viscosity is higher, because of the interaction between solute lignin/hemicelluloses and solvent water, and the aggregation of lignin with itself, hemicelluloses with itself, and lignin wit...

Acid hydrolysis is an essential step in converting polysaccharides to monosaccharides for the production of fuels and chemicals. The prehydrolysis liquor (PHL) from the kraft-based dissolving pulp production process contains mainly oligosugars with a minor amount of monosugars. In this study, the influence of process conditions, including the sulfuric acid concentration, temperature, and time on the PHL hydrolysis was thoroughly investigated in order to get maximum monosugar concentration with minimal degradation of sugars. The maximum monosugar concentration was obtained at 130 °C for 20 min when the hydrolysis was carried out with 1.78% H2SO4. A high acid concentration (3.33%) increased furfural formation and decreased the monosugar concentration. Acetic acid is generated from the acetyl groups bound to the dissolved hemicelluloses, resulting in a significant increase in the acetic acid concentration in the PHL.