Dispersion of supercritical carbon dioxide to [Emim] [BF4] with a T-junction tubing connector

The two-phase mixtures organized by ionic liquids (ILs) and carbon dioxide (CO2 ) are green systems for creation and purification of fine chemicals and natural products. Owing to the very low vapor pressure of ILs, the mixture of supercritical CO2 (ScCO2 ) and IL has asymmetrical solubility, which is special for engineering application. However, due to the high viscosity of IL and the large density difference between IL and ScCO2 , they are difficult to well mix in common chemical engineering equipment. To intensify the contact of ScCO2 and IL, we proposed a micromixing technique to disperse ScCO2 into a representative IL, 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4] as sub-millimeter scaled bubbles. The results showed that 0.3-1.2 mm average diameter's ScCO2 bubbles were cut ruptured by the continuous [Emim] [BF4] phase in a 0.75 mm inner diameter T-junction connector. To further investigate the bubble generation law, the viscosity of CO2 saturated [Emim] [BF4] was determined at different temperatures and pressures. The trend of size variation exhibited that the bubbles were generated from dripping flow at Ca < 0.05, but from jetting flow at Ca > 0.05. In addition, the normalized bubble diameters fit well with the two-phase microflow models obtained at atmosphere pressure.