Fractionation of woodmeal by prehydrolysis and thermal organosolv. Alkaline depolymerization, chemical functionality, and molecular weight distribution of recovered lignins and their fractions

Abstract

. Can. J . Chem. 71, 779 (1993). Thermal organosolv glycol lignins and their fractions have been characterized by means of elemental composition, molecular weight distribution, and 'H and I3c NMR spectroscopy. Fractionation of each lignin by sequential solvent extraction produced fractions of increasing molecular weight and polydispersity. Structures in the highest molecular weight fractions were found to be linked by a high proportion of P-0-4 type bonds, whilst the lowest molecular weight fractions consisted of a high content of saturated aliphatic side-chain structures. A noticeable difference in the content of carbohydrate contaminants in both starting lignins indicated the formation of relatively stable lignin-carbohydrate complexes, especially in the lignin recovered from pretreated wood. In addition, depolymerization of the lignins and their fractions to monomeric compounds was explored using alkaline hydrolytic and nitrobenzene oxidative routes. The highest molecular weight fractions from each lignin were identified as the best candidates for production of useful monomeric phenolic compounds. En se basant sur la composition ClCmentaire, la distribution des poids molCculaires et la RMN du 'H et du I3c, on a caractCrisC les lignines thermiques de l'organosolv glycol et leurs fractions. Le fractionnement de chaque lignine par extraction ~Cquentielle par les solvants a fourni des fractions de poids molCculaires et de polydispersitCs croissants. On a trouvC que les structures des fractions de poids molCculaires les plus ClevCs sont likes en grande partie par des liaisons de type P-0-4 alors que celles des fractions de poids molCculaires plus faibles comportent de grandes quantites de chaines laterales aliphatiques saturkes. On a not6 une difference notablehans le contenuen hydrates de carbone des deux lignines; elle indique qu'il y a formation de complexes lignine -hydrate de carbone relativement stables, particulikrement dans la lignine rCcupCrCe du bois prCtraitC. On a de plus examine la dCpolymCrisation des lignines et de leurs fractions en composCs monomeres par hydrolyse alcaline et par oxydation avec du nitrobenzkne. Pour la production de composCs phCnoliques monomkres utiles, on a identifiC que les fractions de poids molCculaires les plus ClevCs de chacune des lignines seraient les plus appropriCes.[Traduit par la rCdaction]

Fractionation of Organosolv Lignin Using Acetone:Water and Properties of the Obtained Fractions

“…In order to solve the technical issues associated with the heterogeneity of lignin, a variety of lignin fractionation methodologies have been proposed in the literature. The proposed methods result in relatively homogeneous lignin fractions and a better understanding of its composition, − manufacturing processes, − and utility as a phenolic compound; , these methods also facilitate subsequent melt spinning efforts. , …”

“…7 In order to solve the technical issues associated with the heterogeneity of lignin, a variety of lignin fractionation methodologies have been proposed in the literature. The proposed methods result in relatively homogeneous lignin fractions and a better understanding of its composition, 8−11 manufacturing processes, 12−14 and utility as a phenolic compound; 15,16 these methods also facilitate subsequent melt spinning efforts. 17,18 In this study, we investigated a simple and environmentally friendly method for lignin fractionation and examined the lignin molecular weight homogeneity, functional groups, and physical and antioxidant properties.…”

Controlled Release of a Herbicide from Matrix Granules Based on Solvent-Fractionated Organosolv Lignins

“…Sequential Solvent Extraction. Sequential solvent extraction has been successfully used to separate and characterize lignin in terms of molecular weight distribution and group functionality (Thring & Chornet, 1993;Thring et al, 1996). In this study, an organosolv lignin (Alcell lignin) was fractionated into three molecular mass groups by sequential solvent extraction with diethyl ether and methanol according to Thring et al (1996).…”

Fractional Precipitation of Softwood Kraft Lignin: Isolation of Narrow Fractions Common to a Variety of Lignins

“…In order to solve the technical issues associated with the inherent heterogeneity of technical lignins, a variety of lignin fractionation methodologies have been proposed in the literature. These efforts that have offered relatively homogeneous lignin fractions have aided our understanding of its composition, − various details of the manufacturing processes, − and its utility as phenolic compounds. − …”