New Ionic Liquid for the Dissolution of Lignin

Abstract

This work aims to develop a new ionic liquid, used as an aprotic green ä solvent, to dissolve kraft lignin from black liquor. The kraft lignin was extracted through precipitation with carbon dioxide at atmospheric pressure. 1,.0]undec-7-ene-based ionic liquids were obtained by quaternization of the nitrogen atom with a hydrogen atom or an alkyl chain. The yields of the synthesis of the ionic liquids varied between 76 and 80%. Dissolving experiments were carried out using the lignin isolated from the black liquor of a kraft process. Up to 20% (w/w) of the lignin can be dissolved in butyl-1,8 . The time it takes to dissolve the lignin in these three liquids shows that its solubility is influenced mostly by the nature of the cations. The lignin solubility was reduced in relation to the increased length of the grafted carbon chain. The thermogravimetric analysis (TGA) showed these liquids can be used as lignin solvents from room temperature up to 300 °C (onset of degradation). Steric exclusion chromatography showed a slight decrease (6%) in the molecular weight of the lignin dissolved in these ionic liquids.

Lignin solubility in non‐imidazolium ionic liquids

“…On the other hand, it is known that certain ionic liquids (ILs) can efficiently dissolve lignocellulosics . However, cellulose has received most of the attention and few reports appear on dissolution of lignin in ILs . 1‐Butyl‐3‐methylimidazolium chloride, 1,3‐dimethylimidazolium methyl sulfate and 1‐ethyl‐3‐methylimidazolium acetate appear to be good, mild solvents for lignin, with for instance for 1,3‐dimethylimidazolium methyl sulfate lignin solubilities up to 344 g L ‐1 .…”

Opportunities of Ionic Liquids for Lignin Utilization from Biorefinery

“…With the increasing interests in the use of lignin as raw feedstock for new materials and chemicals production, the search of robust solvent for lignin has been obtained much attention, as facile dissolution of lignin can significantly facilitate its structural characterization and valorization. Recent studies have demonstrated that ethylene glycol, DMSO, ionic liquids, γ‐valerolactone, and Tween‐80/H 2 O are able to dissolve up to 70 wt% lignin . Although the lignin dissolution mechanism are not still well understood so far in solvent, it is commonly proposed that the hydrogen bond formation, and non‐covalent π–π interactions between lignin and solvents are the primary forces to promote the dissolution of lignin in solvents.…”

“…Although the lignin dissolution mechanism are not still well understood so far in solvent, it is commonly proposed that the hydrogen bond formation, and non‐covalent π–π interactions between lignin and solvents are the primary forces to promote the dissolution of lignin in solvents. Among of these solvents, ionic liquids have been obtained particular interests due to its particular chemo‐physical properties comparing to traditional molecular solvents ,…”

Flame Retardant-Functionalized Cotton Cellulose Using Phosphonate-Based Ionic Liquids

“…In order to improve the cellulose dissolution process, researchers and industrialists have investigated greener and less-destructive techniques as the direct dissolution of cellulose substrates. N-methylmorpholine N-oxide (NMMO) in its monohydrate form is efficient to dissolve a high amount of cellulose (up to 25% and typically 12-14% in technical applications) and is used at the industrial scale liquids (ILs) known as green solvents, because of their low volatility and good thermal stability, have also attracted attention due to their high capacity to dissolve cellulose (typically 20%) [1,[3][4][5][6][7] as well as other biopolymers such as lignin [6,[8][9][10][11], zein proteins or starch [12].…”