Efficient fixation of CO2 into propylene carbonate with [BMIM]Br in a continuous-flow microreaction system

Utilization of carbon dioxide (CO2) is of great significance in the development of CO2 absorption and the solution of greenhouse gas effect. Highly efficient conversion of CO2 into cyclic carbonate with green catalysts is essential for the more sustainable expansion of CO2 fixation. Traditional batch reactor is limited by low efficiency, high cost and low security. Meanwhile, continuous flow system showcased a myriad of virtues, including shortening the residence time from hours to seconds, and decreasing reaction temperature, and possessing the nature of easy industrial scale-up. In this paper, a continuous-flow microreaction system was developed to synthesis propylene carbonate (PC) from propylene oxide (PO) and CO2 using 1-butyl-3-methylimidazolium bromide ([BMIM]Br) as catalyst. By observing the flow patterns inside microreaction system, the effects of reaction temperature, molar fraction of catalyst, operating pressure, residence time, molar ratio of CO2/PO as well as recycling performance of catalyst on the overall performances were comprehensively evaluated into details. Under different reaction conditions, the flow patterns were set to vary between slug flow and annular flow. The results showed that the yield of propylene carbonate (PC) can reach 99.7% at 140 °C and 3.0 MPa with the residence time of 166 s, while the recycling performance of the designed system greatly conforms the future trend of green chemistry.