Aerocellulose from cellulose–ionic liquid solutions: Preparation, properties and comparison with cellulose–NaOH and cellulose–NMMO routes

Ultra-light and highly porous cellulose material, aerocellulose, is prepared via cellulose dissolution in imidazolium-based ionic liquids, 1-ethyl-3-methylimidazolium acetate (EMIMAc) and 1-butyl-3-methylimidazolium chloride (BMIMCl), followed by regeneration and drying in supercritical CO2 conditions. Regeneration kinetics of cellulose in water is studied. The diffusion coefficients of EMIMAc and BMIMCl were obtained using a Fickian approach; they are analysed as a function of cellulose concentration and compared with the previously obtained values for NaOH and N-methyl-morpholine N-oxide (NMMO). Density, morphology and porosity of aerocellulose from cellulose–ionic liquid solutions are investigated and compared with the corresponding values from NaOH and NMMO routes. The mechanical properties of aerocelluloses under compression from all three routes are studied and correlated with the moduli obtained from mercury porosimetry. For the ionic liquid and NaOH routes the Young's modulus scales aerocellulose density with the exponent close to three, a value typical for silica aerogels.