Thermal aging of 1-alkyl-3-methylimidazolium ionic liquids and its effect on dissolved cellulose
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Falk Liebner
Abstract
The thermal degradation products of 1-alkyl-3-methyl-imidazolium-type ionic liquids (e.g., BMIM, EMIM), which are commonly used in cellulose chemistry, were identified. Imidazole (5), N-methylimidazole (6), and N-alkylimidazoles (7, 8) are the main products. Moreover, dimeric substituted imidazoles (9–11) were found carrying a methylene bridge formed from the N-methyl structure. The former 1-alkyl group (butyl or ethyl) was not present in any of the dimeric compounds. The N-methylene intermediate (12) acts as a precursor for the substituted imidazoles linked by a methylene group. All thermal degradation products are bases and catalyze the previously described reaction between the reducing end of celluloses and 1-alkyl-3-imidazolium cations. To minimize this side reaction, ionic liquids have to be liberated from such basic compounds prior to application as cellulose solvents. In this regard, the usage of “recycled” (and unpurified) ionic liquids has to be treated with caution.
©2010 by Walter de Gruyter Berlin New York
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- Meetings
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Articles in the same Issue
- Original Papers
- Recombinant manganese peroxidase (rMnP) from Pichia pastoris. Part 1: Kraft pulp delignification
- Recombinant manganese peroxidase (rMnP) from Pichia pastoris. Part 2: Application in TCF and ECF bleaching
- The role of hydroxyl and oxyl anion radicals in selectivity of oxygen delignification
- Thermal aging of 1-alkyl-3-methylimidazolium ionic liquids and its effect on dissolved cellulose
- Synchrotron X-ray fiber diffraction study on the thermal expansion behavior of cellulose crystals in tension wood of Japanese poplar in the low-temperature region
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- Obituary
- Dion Chen-Loung Chen (1930–2009)
- Meetings
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