2-35: Fractionation and characterization of lignin extractives from E-AFEXTM 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 remove lignin from lignocellulosic biomass. As a result, pretreated feedstocks contain highly digestible carbohydrate content and significantly reduced lignin content. Depending on the pretreatment conditions, is possible to observe variations on the selectivity during lignin solubilization. Temperature, ammonia concentration and solvent type are the major factors that contribute to a selective lignin solubilization and further extraction. 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 a cleaner lignin fraction. For this purpose, precipitation and filtration based methods were applied. In this work, multiple fractions generated from the E-AFEX^TM extractives from pretreated corn stover were characterized by several techniques, which include GPC, Tg, 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.  Further the benefits of this new pretreatment methodology to downstream processing are presented in comparison with conventional AFEX^TM.