Application of a depolymerization model for predicting thermochemical hydrolysis of hemicellulose.

Literature data were collected and analyzed to guide selection of conditions for pretreatment by dilute acid and water-only hemicellulose hydrolysis, and the severity parameter was used to relate performance of different studies on a consistent basis and define attractive operating conditions. Experiments were then run to confirm performance with corn stover. Although substantially better hemicellulose sugar yields are observed when acid is added, costs would be reduced and processing operations simplified if less acid could be used while maintaining good yields, and understanding the relationship between operating conditions and yields would be invaluable to realizing this goal. However, existing models seldom include the oligomeric intermediates prevalent at lower acid levels, and the few studies that include such species do not account for the distribution of chain lengths during reaction. Therefore, the polymeric nature of hemicellulose was integrated into a kinetic model often used to describe the decomposition of synthetic polymers with the assumption that hemicellulose linkages are randomly broken during hydrolysis. Predictions of monomer yields were generally consistent with our pretreatment data, data reported in the literature, and predictions of other models, but the model tended to overpredict oligomer yields. These differences need to be resolved by gathering additional data and improving the model.