Revealing the effect of water on the CO2-ionic liquid system in microchannels: Physical properties, hydrodynamics and mass transfer behavior

Microchannels and ionic liquids as media of process intensification have stimulated researchers’ attention. Herein, the effect of water on the physical properties, hydrodynamics, and mass transfer behavior of CO 2 -ionic liquid systems in microchannels was unraveled. The introduced water resulted in a significant reduction in viscosity, an increase in bubble size, a shift of the transition line between bubble and Taylor flow towards a low-speed region, and a transformation of bubble morphology from bullet-shaped to ideal bubbles. As a result, bubble length and gas–liquid contact area increased. However, the added water weakened the hydrogen-bond network structure of [BMIM]BF 4 in solutions, accelerated saturation of the liquid film, and reduced the mass transfer rate ( k L ). The predominant drop in k L caused a reduction in the liquid-phase volume mass transfer coefficient ( k L a ), even though the gas–liquid contact area ( a ) increased. Additionally, correlations for predicting bubble length and liquid-phase volume mass transfer coefficients were proposed.