Gas Hold-up Profiles Investigation in Ionic Liquid Column

Ionic liquids (ILs) are melts of salts which have much lower melting points than normal salts, usually less than 373K. The compounds contain many ion-pairs, not like molecular compounds, such as water and many other organic solvents. In contrast with salt solutions, the ILs consist solely of ions, without the presence of any solvent. They have a non-measurable vapour pressure, high thermal stability, ionic conductivity and a large electrochemical window and are able to solvate a variety of organic and inorganic species. These intrinsically useful characteristics have led to ionic liquids being regarded as greener alternatives to volatile organic solvents, namely as reaction media for synthesis, catalysis and biocatalysis In present work, the gas phase was air and the liquid phase was BMImBF4. The electrical resistance tomography (ERT) has been for the first time extended to measure void fraction wave characteristics in a bubble column (Fig.1, 0.203m diameter, 2.5m height) under high temperature (up to 473K) and high pressure (up to 3MPa). The effects of IL¡¯s temperatures, column pressure, axial liquid height (HD/D) and superficial gas velocities for radial variation of gas hold up and local holdup have been investigated. The holdup derived from ERT was also compared with the hold-up values measured by pressure transmitters. The hold-up profiles were found to depend strongly on superficial gas velocities and IL¡¯s temperature (Fig.2), while column pressure and axial liquid height (HD/D) influenced slightly(Fig.3). Key words: Ionic liquid; Bubble column; Hold up; Electrical resistance tomography. Acknowledgement: This work was supported by the National Natural Science Funds for Distinguished Young Scholar (No. 20625618) and the Instrument Developing Project of the Chinese Academy of Sciences( No. Y2005013)