6 results
Search Results
2. On the mechanism of the unwanted acetylation of polysaccharides by 1,3-dialkylimidazolium acetate ionic liquids: part 2-the impact of lignin on the kinetics of cellulose acetylation.
- Author
-
Abushammala, Hatem, Hettegger, Hubert, Bacher, Markus, Korntner, Philipp, Potthast, Antje, Rosenau, Thomas, and Laborie, Marie-Pierre
- Subjects
ACETYLATION ,POLYSACCHARIDES ,LIGNINS ,IONIC liquids ,IMIDAZOLES - Abstract
Cellulose acetylation has been reported as a side reaction of cellulose treatment with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) (Karatzos et al. in Cellulose 19:307-312, 2012) and other 1,3-dialkylimidazolium acetate ionic liquids. 1-Acetylimidazole (AcIm), an [EMIm][OAc] impurity, has been found to be the actual acetylating agent (Zweckmair et al. in Cellulose 22:3583-3596, 2015), and the degree of acetylation was relatively low, below a DS of approx. 0.1%. Higher degrees of cellulose acetylation (DS > 10%) have been observed when the entire wood was mixed with [EMIm][OAc] instead of cellulosic pulp only (Abushammala et al. in Carbohydr Polym 134:609-616, 2015). In this paper, we explore the impact of wood constituents, mainly lignin, on cellulose acetylation using AcIm. The results demonstrate that lignin itself can be readily acetylated upon mixing with AcIm, and-noteworthy-that lignin presence significantly accelerates cellulose acetylation. The initial rate of cellulose acetylation by AcIm increased from 1.8 to 4.7%/h when only 1% of lignin, based on cellulose mass, was added. A mechanistic study employing cellulose and lignin model compounds showed lignin to be more susceptible to acetylation than cellulose and to act as an intermediate acetyl group source for further cellulose acetylation in a catalytic scenario. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
3. Improved Acetylation Efficacy of Wood Fibers by Ionic Liquid Pretreatment.
- Author
-
Xiaoping Shen, Yanjun Xie, and Qingwen Wang
- Subjects
ACETYLATION ,IONIC liquids ,POPLARS ,IMIDAZOLES ,LIGNINS ,ACETIC anhydride - Abstract
Poplar wood fibers (WFs) were pretreated with ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) at 125 °C for 1 h, and the influence of the wood loadings (5%, 15%, 30%, and 50%) on the pretreatment efficiency and downstream acetylation was studied. The crystallinity and lignin content of the WFs decreased after IL pretreatment at low wood loadings, especially at 5%. Wood fiber acetylation was performed under a molar ratio (acetic anhydride/-OH in the WFs) of 2:1, with toluene as the reaction medium and pyridine as the acid capturer. Ionic liquid pretreatment at 5% and 15% loading greatly contributed to the increase of weight percent gain (WPG) after acetylation, leading to much higher reaction efficiency, or lower energy consumption. The acetylated products that underwent pretreatment (mainly at 5% loading) had slightly higher thermal stability than those that did not undergo pretreatment. The crystallinity and moisture sorption ability of the products were determined primarily by the WPG value. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. Development of Acidic Imidazolium Ionic Liquids for Activation of Kraft Lignin by Controlled Oxidation: Comprehensive Evaluation and Practical Utility.
- Author
-
Klapiszewski, Łukasz, Szalaty, Tadeusz J., Kurc, Beata, Stanisz, Małgorzata, Zawadzki, Bartosz, Skrzypczak, Andrzej, and Jesionowski, Teofil
- Subjects
IMIDAZOLES ,IONIC liquids ,LIGNINS ,PROTONS ,ELECTRONS ,ELECTROCHEMISTRY ,OXIDATION - 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,
13 C 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. [ABSTRACT FROM AUTHOR]- Published
- 2018
- Full Text
- View/download PDF
5. Effects of reaction conditions on the acid-catalyzed hydrolysis of miscanthus dissolved in an ionic liquid.
- Author
-
Dee, Sean and Bell, Alexis T.
- Subjects
HYDROLYSIS ,MISCANTHUS ,ACID catalysts ,IONIC liquids ,IMIDAZOLES ,HEMICELLULOSE ,LIGNINS ,SUGAR - Abstract
Experiments were conducted to study the effects of reaction conditions on the hydrolysis of miscanthus dissolved in 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) catalyzed by H
2 SO4 . It was determined that while there is a small co-inhibition effect associated with the simultaneous hydrolysis of the cellulosic and hemicellulosic portions of miscanthus, the largest rate decreases were observed for the hydrolysis of the hemicellulosic portion. This rate decrease was attributed to the chemical linkage between hemicellulose and lignin in miscanthus, which could be broken with chemical pretreatment. While chemical pretreatment increased the rate of the hydrolysis of the hemicellulosic component, delignification showed no further benefit. The rate of hydrolysis was determined to be first order in concentrations of β-1,4 glycosidic linkage and acid, and zero order in water concentration. The activation energy for the hydrolysis of the glycosidic linkages in the cellulosic and hemicellulosic components were determined to be 95 kJ mol−1 and 114 kJ mol−1 respectively. Progressive addition of water during the first hour of the reaction increased conversion and selectivity to saccharine products, while limiting dehydration of the sugars formed. The conversion of the cellulosic portion of miscanthus could be increased after the first hour of the reaction by increasing the reactor temperature. While miscanthus is only partially soluble in [Emim][Cl], it was found that the initial miscanthus loading could be increased to 9 wt% before significant yield decreases attributed to solubility limitations of the cellulosic component were observed. By proper adjustment of reaction conditions, it was possible to achieve yields of sugars approaching 84% from the cellulosic and hemicellulosic components of miscanthus, with minimal dehydration of the sugars to furans. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
6. Composite fibers spun directly from solutions of raw lignocellulosic biomass dissolved in ionic liquids.
- Author
-
Sun, Ning, Li, Weiying, Stoner, Breena, Jiang, Xinyu, Lu, Xingmei, and Rogers, Robin D.
- Subjects
FIBROUS composites ,RAW materials ,LIGNOCELLULOSE ,BIOMASS ,IONIC liquids ,IMIDAZOLES ,LIGNINS ,GLASS transition temperature - Abstract
Lignocellulosic biomass composite fibers (southern yellow pine and bagasse) were successfully prepared directly from the ionic liquid, 1-ethyl-3-methylimidazolium acetate ([C
2 mim]OAc) with a dry-jet wet spinning process using short dissolution times (10–30 min) and temperatures above the glass transition temperature of lignin. Fibers could not be spun at all from solutions of pine dissolved using previously reported dissolution methods (110 °C, 16 h), while bagasse fibers spun using the higher temperature/shorter time method were stronger than those obtained using the lower temperature/longer time method. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.