Development of Acidic Imidazolium Ionic Liquids for Activation of Kraft Lignin by Controlled Oxidation: Comprehensive Evaluation and Practical Utility

Abstract

A novel, eco‐friendly method for the activation of lignin by controlled oxidation was studied. The results obtained for six acidic imidazolium ionic liquids containing the hydrogen sulfate anion were compared. The key goal of this research was to increase the content of carbonyl groups in the lignin structure because these may play the main role in the transport of protons and electrons in active materials for electrochemical applications. By means of a variety of analytical techniques (FTIR, 13C CP/MAS NMR, and X‐ray photoelectron spectroscopy; selected reactions to determine the presence of carbonyl groups; SEM; zeta‐potential analysis; thermogravimetric analysis/differential thermogravimetric analysis; and porous structure analysis), it was determined that the product obtained after treatment with 3‐cyclohexyloxymethy‐1‐methylimidazolium hydrogen sulfate had favorable properties, in terms of the target application. Electrochemical tests proved that the obtained materials could be used as anodes in lithium batteries. The results show that the activation of lignin with ionic liquids can increase its capacity and maintain stability.

Functional MgO–Lignin Hybrids and Their Application as Fillers for Polypropylene Composites

“…In each case, there was a permanent connection between the components, as a result of which hybrid materials belonging to the first class (with physical connection of components, mainly through hydrogen bonds) [14,[17][18][19] or the second class (chemical combination of components with the formation of covalent bonds) were obtained, depending on the method used [13,15]. In the chemical method, it was important to modify the inorganic matrix properly and activate the biopolymer, which was mainly obtained by oxidation with inorganic compounds [13,15] or, alternatively, with ionic liquids [20]. In the case of the MgO-lignin systems used in this publication and their use as environmentally friendly polymer fillers, it is sufficient to physically connect the components without the need to conduct prior chemical modifications.…”

“…At temperatures above~200 • C this biopolymer is gradually decomposed, which ultimately results in its degradation [14,[17][18][19]. Therefore, it seems important to combine lignin with inorganic compounds, including highly thermally stable MgO [20,21]. This gives the opportunity to create new inorganic-organic hybrid materials for specific applications.…”

Dissolution of kraft lignin in alkaline solutions

“…For example, in some electrochemical applications, the activation of lignin is a crucial step in order to increase the quantity of carbonyl groups. This can be achieved by dissolving lignin in ionic liquids [23][24][25]. A strong aqueous alkaline solvent is a preferential system cited in the literature for dissolving kraft lignin but, surprisingly, the solubility of lignin in these systems has not been properly described.…”

Biokatalizatory I Biopolimery W Aspekcie Zrównoważonej Chemii

“…Prowadzone badania, związane z tematyką ligniny, spowodowały w konsekwencji rozwój dodatkowej ścieżki badawczej -próby wykorzystania przyjaznych dla środowiska cieczy jonowych w roli "zielonych", "projektowalnych" związków umożliwiających modyfikację struktury biopolimeru [83][84][85][86]. W tym celu wykorzystano powszechnie znane, relatywnie tanie i przyjazne dla środowiska ciecze jonowe, ale także zaprojektowano grupę nowych ILs, które wykorzystane w warunkach łagodnego utleniania w powietrzu odpowiednio modyfikowały strukturę ligniny zwiększając zawartość ugrupowań karbonylowych.…”