Mass transfer and kinetic behavior studies on cycloaddition of carbon dioxide with propylene oxide catalyzed by ionic liquid in microchannel reactor

The synthesis of propylene carbonate (PC) from CO 2 and propylene oxide (PO) is a typical gas-liquid biphasic system, where gas-liquid mass transfer efficiency significantly influences CO 2 cycloaddition reactions. Here, we proposed a microchannel reaction system for the CO 2 cycloaddition reaction catalyzed by ionic liquid within an aqueous environment. The effect of liquid flow rate, temperature and residence time on gas-liquid flow pattern, catalytic performance and mass transfer were systematically investigated. The results revealed that the PC generation rate reached 560.11 mmol·ml −1 ·h −1 ) at a 50 cm of flow distance under reaction conditions of 105 °C, 2.5 MPa, Q G =176 sccm and Q L =0.3 ml·min −1 . Variations in mass transfer rate and reaction rate at different flow distances were experimentally studied. The reaction efficiency gradually decreased with increasing flow distance, which were attributed to the reduction of mass transfer caused by decreasing bubble velocity. Optimizing bubble velocity at an appropriate position enhanced reaction efficiency by improving mass transfer, achieving a 97.7% PC yield within 2.85 min. Furthermore, a kinetic model coupling intrinsic kinetics with gas-liquid mass transfer was developed for CO 2 cycloaddition reaction. The kinetic model was applied to predict PC reaction rates in microchannel reactors at various temperatures and liquid flow rates, achieving an average relative error of 9.6%.