Thermostability of imidazolium ionic liquids as direct solvents for cellulose

Abstract

Ionic liquids (ILs) exhibit a far lower degradation potential compared to the established direct cellulose solvent N-methylmorpholine- N-oxide monohydrate used in the Lyocell process. Safety parameters such as onset temperature, pressure rise and heat release during exothermicity were measured in imidazolium ILs and solutions of cellulose in ILs by means of DSC, dynamic reaction calorimetry and UV/VIS spectroscopy with a special designed cuvette. Onset temperatures were determined using pressure rise measurement at a threshold value. Initial thermal activities in ILs occurred at much lower temperatures compared to DSC measurements and TGA literature data. For 1-ethyl-3-methylimidazolium acetate (EMIMAc) and 1-butyl-3-methylimidazolium acetate (BMIMAc) the onset temperatures 181 and 179 °C, respectively, were stated first time. Endothermic decomposition of pure EMIMAc is turned to an exothermic event by addition of cellulose accompanied by increased slope of pressure.