Fractionation and characterization of Steam Explosion lignin through neutral and mildly acidic organosolv techniques

Lignocellulosic biomass is the largest pool of renewable org. material in the world. As such it is imperative to develop new methods in order to fully utilize this vast resource. The main problem with lignocellulosic biomass is that due to its recalcitrant nature lignin is frequently considered to be non-​value waste and preferably burned during manufg., to produce energy for the biorefinery. In this study, we present green fractionation methods to ext. higher value lignin fractions from crude "Steam Explosion" lignin, contg. large amts. of insol. material. The lignin was from Italian Bioproducts, IBP, and produced as a side product using 2nd generation bioethanol process PROESA technol. and poplar as feedstock. Insol. lignin is both difficult to characterize and to refine into valuable products. The extn. methods compared in this study include ethanol extn., formic acid extn. and extn. with a mixed solvent contg. equal amt. of formic acid and ethanol. The extd. lignins had significantly improved soly. characteristics compared to the initial steam explosion lignin. For example, in the case of ethanol extn. with a yield of 17,​5 % (wt.​/wt.)​, the isolated lignin was completely sol. e.g., in acetone and 1,​4-​dioxane. The lignin structure contained all the native lignin linkage types, such as β-​O-​4, β-​5 and β-​β, indicating, that the mol. structure remained to a high extent intact and contained very few carbohydrates according to HSQC-​NMR and pyrolysis-​GC​/MS. The MW value of the fraction was detd. to be 2,​2 kDa and the mol. wt. range was below 10 kDa.