Impact of Ionic Liquid 1-Ethyl-3-Methylimidazolium Acetate Mediated Extraction on Lignin Features

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.

Acetyl Groups in Typha capensis: Fate of Acetates during Organosolv and Ionosolv Pulping

“…Typha capensis sample was uprooted, cut to ≤2 cm pieces, and sundried. The protocol edited by Hames et al [23] was used for sample preparation as previously described [16]. Briefly, the cut raw TC was oven dried at 40 °C for 48 h, milled to obtain particle size ≤ 0.4 mm.…”

“…The procedure published by Sun et al [26] was used with slight modifications as described previously [16]. Briefly, TC extr was weighed in a conical flask and 1-ethyl-3-methylimidazolium acetate was added to obtain a biomass to solvent ratio of 1:20 ( w / w ).…”

“…In recent investigations of TC, we reported that native TC comprised of ca. 18% extractives, 39% cellulose, 19% hemicellulose and 23% lignin [16]. Furthermore, it was shown that TC grass can be effectively fractionated with organosolv and [EMIm][OAc] pulping, releasing distinct lignin residues [16].…”

“…18% extractives, 39% cellulose, 19% hemicellulose and 23% lignin [16]. Furthermore, it was shown that TC grass can be effectively fractionated with organosolv and [EMIm][OAc] pulping, releasing distinct lignin residues [16]. While FTIR of TC MWL revealed acetylation, acetate bands were not detected in EOL and ILL, perhaps due to method-sensitivity limits [16].…”

“…Furthermore, it was shown that TC grass can be effectively fractionated with organosolv and [EMIm][OAc] pulping, releasing distinct lignin residues [16]. While FTIR of TC MWL revealed acetylation, acetate bands were not detected in EOL and ILL, perhaps due to method-sensitivity limits [16]. Therefore, to provide a thorough view of the extent of acetylation in native TC and monitor potential acetate transfer during TC pulping, more sensitive analytical methods are required.…”