Abstract
This study aims at investigating the impact of ionic liquid extraction on lignin structure by studying the mechanism of lignin depolymerization in 1-ethyl-3-methylimidazolium acetate EMIM[OAc]) and comparing it with that of organosolv and milled wood methods. Ionic liquid mediated lignin (ILL) using EMIM[OAc]), ethanol organosolv lignin (EOL) and milled wood lignin (MWL) were isolated from Typha capensis (TC) and subjected to several analytical characterizations. Experimental data shows that ILL exhibited a relatively lower degree of condensation, lower aromatic C-C structures and a higher aliphatic OH with values of 0.42/Ar, 1.94/Ar and 1.33/Ar moieties compared with EOL values of 0.92/Ar, 2.22/Ar and 0.51/Ar moieties respectively. The ILL was depolymerized under mild conditions giving relatively higher β-aryl ether linkages content, higher molecular mass, and exhibited closer structures and reactivity to native lignin than EOL. These insights on TC lignin depolymerization in EMIM[OAc]) acetate may contribute to better value-addition of lignocellulosic biomass.
Highlights
IntroductionA pulp with good enzymatic digestibility, and high-quality lignin, can be obtained, allowing for multiple high value products [2] [3] [4]
This study aims at investigating the impact of ionic liquid extraction on lignin structure by studying the mechanism of lignin depolymerization in 1-ethyl3-methylimidazolium acetate EMIM[OAc]) and comparing it with that of organosolv and milled wood methods
The cleavage of ether linkages is primarily responsible for lignin breakdown in both ionic liquid and organosolv methods
Summary
A pulp with good enzymatic digestibility, and high-quality lignin, can be obtained, allowing for multiple high value products [2] [3] [4]. More recently Ionic liquids (ILs) have been used for biomass fractionation [5] [6] [7] [8] [9]. Among all the ILs used, EMIM [OAc] is powerful, as the treatment conditions can be turned effectively to fractionate lignin and cellulose rich pulp from lignocellulosic biomass [5], and collect intact cellulose nanocrystals [10] [11]. In view of a biorefinery deliverables of several high value products, EMIM [OAc] is very interesting. The delignification chemistry of EMIM [OAc] and the resulting lignin structure is not fully understood
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