AbstractPhase transformations in microcrystalline cellulose (MCC) were studied following dissolution of 5, 10, and 20 wt. % MCC in the ionic liquid 1-butyl-3-methylimidazolium formate (BMIMFmO) and regeneration via water. BMIMFmO was found to be useful as a non-derivatizing solvent for cellulose without the need for any pre-treatment. Wide angle X-ray scattering indicated that a phase transformation from cellulose I to either a poorly crystalline form of cellulose I and/or cellulose II occurs during regeneration after dissolution in BMIMFmO. The dissolution time affected the resulting microstructure of the regenerated cellulose. Thermogravi-metric analysis showed that regeneration from the ionic liquid lowers the decomposition onset temperature and increases the char yield when compared with the as-received MCC.