(547a) Fractionation and Characterization of Lignin Extractives From E-AFEX(TM) Pretreatment Process

Extractive AFEX^TM (E-AFEX^TM) is a novel pretreatment technology that is able to simultaneously convert cellulose I to cellulose III and partially extract lignin from lignocellulosic biomass. As a result, pretreated feedstocks contain highly digestible carbohydrate content and significantly reduced lignin content. Depending on the pretreatment conditions, it is possible to obtain variations in the selectivity towards lignin solubilization. Temperature, ammonia concentration and co-solvent type are the major factors that contribute to a selective lignin solubilization and subsequent fractionation. Some pretreatment conditions tend to solubilize ash and hemicellulose residues along with lignin. However, since most applications for lignin require low ash and carbohydrate contents, these extractives have been further fractionated to obtain varying purity lignin fractions. For this purpose, solvent precipitation and filtration based methods weredeveloped to fractionate lignin. In this work, multiple fractions generated from the E-AFEX^TM extractives generated from pretreated corn stover were characterized by several techniques, which include GPC, TGA, ¹³C-NMR, ¹H-NMR and 2D NMR. A comparison of E-AFEX^TM lignin with other commercial lignin sources is also presented here. The level of lignin extraction and cellulose III conversion was correlated with cellulose digestibility for corn stover.  Furthermore the benefits of this new pretreatment methodology to downstream processing are presented in comparison with conventional AFEX^TM.