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Title: | Uncovering the potentialities of protic ionic liquids based on alkanolammonium and carboxylate ions and their aqueous solutions as non-derivatizing solvents of Kraft lignin |
Author: | Dias, Rafael M. Lopes, André M. da Costa Silvestre, Armando J.D. Coutinho, João A. P. Costa, Mariana C. da |
Keywords: | Protic ionic liquids Kraft lignin solubility Hydrotropic effect Ionic liquid recycling Non-derivatizing solvents |
Issue Date: | Jan-2020 |
Publisher: | Elsevier |
Abstract: | The present study scrutinized in depth the ability of alkanolammonium-based Protic Ionic Liquids (PILs) with carboxylate anions to dissolve Kraft lignin at 323.15 K. A focus was put on understanding the role of both PIL ions and water on the dissolution process. The results demonstrated that the anion plays a more important role in lignin dissolution than the cation. Furthermore, lignin dissolution was favored by increasing the alkyl chain of the carboxylate anion, while a smaller cation with lower number of hydroxyalkyl groups performed better. Among the studied solvents, the 2-hydroxyethylammonium hexanoate (HEAH) displayed the highest lignin solubility (37 wt%). In general, the addition of water had a negative influence on lignin solubility with the tested PILs. A sharp decrease in lignin solubility curves of 2-hydroxyethylammonium formate (HEAF) and acetate (HEAA) was observed, while a more softly effect was observed for 2-hydroxyethylammonium propionate (HEAP) and HEAH with the addition of water. However, a distinct behavior was observed for 2-hydroxyethylammonium octanoate (HEAO) that acted as hydrotrope enhancing lignin solubility in aqueous solutions to a maximum value at 40 wt% water content. Furthermore, by increasing the temperature, the lignin solubility was favored due to endothermic behavior of lignin dissolution process. The dissolution of Kraft lignin was also performed at 393.15 K to unravel any lignin modification unleashed by PILs. GPC, FTIR-ATR and 2D NMR were employed for lignin characterization and the changes observed between native lignin and recovered lignin samples were negligible demonstrating the non-derivatizing char- acter of the PILs. Moreover, the recycle of 2-hydroxyethylammonium propionate (HEAP) was successfully de- monstrated for at least 3 cycles. In this way, PILs are herein revealed as promising solvents to apply in lignin valorization towards more efficient and eco-friendly processes. |
Peer review: | yes |
URI: | http://hdl.handle.net/10773/28200 |
DOI: | 10.1016/j.indcrop.2019.111866 |
ISSN: | 0926-6690 |
Appears in Collections: | CICECO - Artigos |
Files in This Item:
File | Description | Size | Format | |
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j.indcrop.2019.111866.pdf | 2.84 MB | Adobe PDF | View/Open |
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