Room-Temperature Ionic Liquids (RTILs) are typically constituted of bulky, asymmetric and charge-diffuse ions,1 and are characterised by their high densities and vanishingly low vapour pressures. Over the course of the past two decades, the applications of ionic liquids have become very varied and far-reaching, foremost as solvents for sustainable processes, electrolytes, and recently in deconstruction of lignocellulosic biomass.2 Cellulose is the world’s largest biorenewable resource. Strong intermolecular and intramolecular H-bonds hold together the individual polymer strands, rendering cellulose insoluble in the majority of conventional solvents; this ‘recalcitrant’ behaviour presents a major challenge to harvesting such an abundant resource. Carboxylate, chloride and dialkyl phosphate ionic liquids are capable of solvating cellulose,2 and represent promising alternatives to the existing and far-from-ideal ‘Lyocell’ and ‘Viscose’ technologies. However, the possibility of decomposition reactions occurring between solvent and solute must be carefully considered. Mixtures of ionic liquids with cellulose, and subsequently with smaller model compounds, were heated to temperatures analogous to cellulose dissolution processes (100 - 120 °C), and were periodically investigated employing a broad range of spectroscopic and chromatographic techniques.3 Dialkylimidazolium carboxylate ionic liquids are not inert towards cellulose, and their tendency to form N-Heterocyclic Carbenes,4 their so- called ‘non-innocent’ nature, plays a vital role. By contrast, chloride anologues retain the beneficial property of good cellulose solubility, whilst lacking the undesirable tendency of form adduct side-products. References 1. J. P. Hallett and T. Welton, Chem. Rev., 2011, 111, 3508. 2. A. Brandt, J. Gräsvik, J. P. Hallett and T. Welton, Green Chem., 2013, 15, 550. 3. M. T. Clough et al., submitted to Green Chem. 4. M. T. Clough, K. Geyer, P. A. Hunt, J. Mertes and T. Welton, Phys. Chem. Chem. Phys., 2013, 15, 20480.

Ionic liquids: Not always innocent solvents for cellulose

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.