Enhancing the stability of ionic liquid media for cellulose processing: acetal protection or carbene suppression?

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Title: Enhancing the stability of ionic liquid media for cellulose processing: acetal protection or carbene suppression?
Authors: Welton, T
Griffith, J
Clough, M
Kuzmina, O
Item Type: Journal Article
Abstract: Although excellent candidate solvents for cellulose, capa-ble of dissolving 20 wt% of the carbohydrate for electro-spinning processes, dialky-limidazolium carboxylate ionic liquids undergo unde-sirable side reactions with the reducing end of saccharides, terminating in an equilibrium concentration of a 2-(hydroxymethyl)-substituted imidazolium ‘adduct’. The addition of small molar quantities of a benign, non-toxic and inexpensive co-solvent, e.g. glycerol, mini-mises the rate of adduct ac-cumulation, thereby enhanc-ing the long-term thermal stability and recyclability of the expensive ionic liquid component. NMR, UV-vis and mass spectrometry ex-periments reveal that the im-proved stability is likely at-tributable to suppression of the transient dialkylimidazol-2-ylidene carbene, via hy-drogen-donation by the pro-tic co-solvent, rather than by cyclic acetal protection of the carbohydrate. The incor-poration of (up to) 10 wt% of glycerol into the solvent mix-ture does not exacerbate the rate of cellulose depolymeri-sation compared to in the neat ionic liquid, and high solubility of cellulose is main-tained. Furthermore, a col-ourimetric comparison of the recovered solvents, following cellulose re-precipitation, demonstrates that glycerol does not increase the concen-tration of contaminant re-ducing sugars in the organic electrolyte.
Issue Date: 4-Apr-2016
Date of Acceptance: 4-Apr-2016
URI: http://hdl.handle.net/10044/1/30607
DOI: https://dx.doi.org/10.1039/C6GC00027D
ISSN: 1463-9262
Publisher: Royal Society of Chemistry
Start Page: 3758
End Page: 3766
Journal / Book Title: Green Chemistry
Volume: 18
Copyright Statement: © The Royal Society of Chemistry 2016
Sponsor/Funder: Engineering & Physical Science Research Council (E
Funder's Grant Number: AERO RB1717
Keywords: Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Science & Technology - Other Topics
Organic Chemistry
03 Chemical Sciences
Publication Status: Published
Appears in Collections:Chemistry
Catalysis and Advanced Materials
Faculty of Natural Sciences

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