(272d) Bubble Behavior in Ionic Liquid [Bmim]BF4
Ionic liquids (ILs) have been widely considered as potential green substitutes for traditional organic solvents in a variety of chemical processes. However, knowledge related to the hydrodynamics of ionic liquids especially the bubble behavior is still very limited compared with the conventional molecular solvents. In this work, a photographic image analysis method was established to study the bubble behavior in ionic liquid [bmim]BF4 by using high speed image pick-up system, operated at 500 frames per second with a resolution of 1280×1024 pixels. The bubble behavior, such asbubble size distribution, average gas holdup, Sauter mean diameter and interfacial area at different gas superficial velocities, liquid temperatures as well as axis positions of the bubble column were investigated. The experimental results showed that the bubble diameter in [bmim]BF4 increased as gas superficial velocity and axis position were raised but decreased with increasing temperature. The total gas holdup in [bmim]BF4increased at increasing temperature due to the decrease of liquid viscosity. The total gas holdup also increased at increasing gas superficial velocity due to the increase of gas momentum which favored the formation of small bubbles. A new correlation based on the experimental data was proposed for the prediction of bubble Sauter diameter in [bmim]BF4. The values predicted by the new correlation are in good agreement with the experimental results with a relative error less than 10%.
 Krishna, R., Ellenberger, J., 1996. Gas holdup in bubble column reactors operating in the churn-turbulent flow regime. AIChE Journal 42, 2627-2634.
 Dong, H., Wang, X., Liu, L., Zhang, X., Zhang, S., 2010. The rise and deformation of a single bubble in ionic liquids. Chemical Engineering Science 65, 3240-3248.