8-04: Role of hemicellulose-lignin oligomers dissolution in flowthrough pretreatment of Miscanthus

Hot water flowthrough pretreatment removes hemicellulose and lignin from biomass, providing a unique opportunity to examine the dynamic deconstruction pattern of various components of biomass, including lignin, hemicellose and their complex. Efficient hot water flowthrough pretreatment ensures high hemicellulose and lignin removal and high sugar yields in subsequent enzymatic hydrolysis that is vital to the economic viability of biomass conversion. More importantly, it is believed that dissolving of higher molecular weight hemicellulose-lignin oligomers could play an important role in explaining why the performance of flowthrough systems differs from conventional batch approaches.

In this presentation, we will show results from a number of studies using flowthrough pretreatment of Miscanthus with hot water for varying temperatures (160-220°C), times (0-120min), and flowrates (1-50mL/min) to understand the influence of pretreatment on lignin and hemicellulose removal into the hydrolyzate as well as on further processing of the resulting pretreated biomass solids. The dynamic characteristics of hemicellulose, lignin, and their complex in the hydrolyzate during pretreatment, including compositions, structural features and solubility will be reviewed. Finally we will present a kinetic model based on this data to compare conventional kinetic behavior versus that by dissolution and solubility limits with reaction and mass transfer effects. The model was further verified using an analog of a lignin-hemicellulose complex. This model was found to provide useful insights into the thermochemical pretreatment mechanism.