(669e) Water-Only Flowthrough Pretreatment of Poplar and Birchwood Xylan

The conversion of lignocellulosic biomass to ethanol requires recovery of the sugars contained in the hemicellulose and cellulose. High temperature water-only pretreatment solubilizes primarily sugars and oligomers in hemicellulose prior to the enzymatic hydrolysis of the cellulose in the remaining solids to glucose. The understanding and kinetic models of hemicellulose hydrolysis are generally simplistic and do not fully address the existence of xylooligomers, lignin, and the interaction of biomass components. Furthermore, pretreatment of cellulosic biomass in the batch reactors typically employed makes the collection of time-dependent data challenging. On the other hand, a fixed bed flowthrough reactor facilitates tracking the release of biomass components as a function of time, thus making it a valuable laboratory tool. Analyzing the flow behavior and release patterns of xylooligomers from poplar and xylan would improve the understanding of the relative importance of mass transfer and kinetics during pretreatment. Analysis of void volume and flow behavior of a fixed bed flowthrough reactor will be determined to help characterize mass transfer in the system. Although lignin morphology is known to change during pretreatment, the cause of these changes is not well-known. It has been suggested that lignin depolymerizes (Li et al., 2007) or melts (Donohoe et al., 2008) during pretreatment. In an attempt to clarify the differences between these mechanisms, the release of lignin and lignin derivatives from poplar are followed over a range of reaction times, temperatures, and flow rates. Finally, pretreatment results from poplar and purified xylan are compared to clarify xylan interactions with other poplar components, such as cellulose and lignin.