Phenolic Group Distribution as a Function of Molecular Weight in Lignins and Their Fractions

Abstract

An analytical approach based on phenol fluorescence labeling with the dansyl fluorophore coupled with gel permeation chromatography using UV and fluorescence detection was applied in an effort to increase the understanding of the phenolic group distribution in different lignin specimens. Selective derivatization with dansyl chloride of lignin phenolic functionalities was quantitatively achieved under mild reaction conditions and was applied to acidolytic and kraft lignins from softwood and hardwood and to kraft lignin fractions obtained by solvent fractionation. Acetylated lignins and labeled lignins were analyzed to discern the lignin aromatic skeleton input from the response of dansyl-linked phenols, successively, allowing for estimation of the phenolic group distribution as a function of molecular weight for different lignins before and after solvent fractionation.

Past to Future: Application of Gel Permeation Chromatography from Petroleomics and Metallopetroleomics to New Energies Applications: A Minireview

“…This finding is particularly interesting for determining the efficiency of pyrolysis processes based on residual lignin fragments after the depolymerization process of RCF. The observations by Van Aelst et al correspond with other studies where lignin fractions exhibited a linear correlation between their size and polarity. − This correlation is expected, considering the polyphenolic structure of lignin, where larger sizes result in a higher number of hydroxyl groups in the fraction …”

Recombinatorial approach for the formation of surface-functionalised alkaline-stable lignin nanoparticles and adhesives

“…When compared to LNPs derived from ethanol fractionation, the ones obtained upon ethyl acetate fractionation, i.e., GlySol EtOAc + Ins EtOAc LNPs, experienced a higher degree of interparticle crosslinking, as reflected by the extent of the dimensional growth upon thermal treatment. The observed higher degree of crosslinking in the case of lignin fractions from ethyl acetate was ascribed to the high selectivity of this solvent in solubilising a low molecular weight, narrowly polydisperse lignin fraction 38,39 which, after functionalisation with epoxy groups, specifically locates on the outer shells of LNPs, as expected from the molecular weight-dependent precipitation mechanism described in the literature, assuming a rather unchanged solubility profile for functionalised lignin fractions under tested conditions. 11 On the other hand, ethanol fractionation resulted in a soluble portion that exhibited a broader molecular weight distribution.…”