, Volume 10, Issue 3, pp 227-236

Inorganic Molten Salts as Solvents for Cellulose

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Abstract

Inorganic molten salts can be used as efficient solvents for cellulose in a wide range of degrees of polymerization. Furthermore, molten salts can be applied as reaction medium for the derivatization of cellulose. For both dissolution and derivatization of cellulose, knowledge of the solution state as well as information about chemical interactions with the solvent system is essential. Using the melts of LiClO4·3H2O, NaSCN/KSCN/LiSCN·2H2O and LiCl/ZnCl2/H2O as cellulose solvents, factors which determine the dissolving ability will be discussed. Besides the specific structure of the molten salt hydrate, the cation and the water content of the melt are the most important factors for the dissolving capability of a molten salt hydrate system. FT-Raman spectroscopy, 7Li and 13C NMR spectroscopy were applied to describe solvent–cellulose interactions and the state of cellulose dissolved in the molten salts. Using Raman and solid state NMR spectroscopy it was proved that cellulose is amorphous in the frozen solvent system. The application of inorganic molten salts as a medium for cellulose functionalization is demonstrated for cellulose carboxymethylation and acetylation.