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The combination of ultrasound and microreactor is an emerging and promising area, but the report of designing high-power ultrasonic microreactor (USMR) is still limited. This work presents a robust, high-power and highly efficient USMR by directly coupling a microreactor plate with a Langevin-type transducer. The USMR is designed as a longitudinal half wavelength resonator, for which the antinode plane of the highest sound intensity is located at the microreactor. According to one dimension design theory, numerical simulation and impedance analysis, a USMR with a maximum power of 100 W and a resonance frequency of 20 kHz was built. The strong and uniform sound field in the USMR was then applied to intensify gas–liquid mass transfer of slug flow in a microfluidic channel. Non-inertial cavitation with multiple surface wave oscillation was excited on the slug bubbles, enhancing the overall mass transfer coefficient by 3.3–5.7 times. [ABSTRACT FROM AUTHOR]

The development of highly efficient processes for the cycloaddition of CO2 with epoxides to produce five-membered cyclic carbonates is a very attractive topic. In this work, the cycloaddition of propylene oxide (PO) and CO2 to give propylene carbonate (PC) is studied in a microreactor using a HETBAB ionic liquid catalyst. The microreactor performance is evaluated by studying the effects of different operating conditions, including reaction temperature, operating pressure, residence time, molar ratio of CO2/PO, and the catalyst concentration in PO. The process characteristics of the reaction concerning the gas–liquid mass transfer and the intrinsic kinetics perspectives are discussed. The results show that the residence time can be dramatically reduced from several hours in a conventional stirred reactor to about 10 s in a microreactor. The yield of PC at 3.5 MPa can reach 99.8% at a residence time of 14 s. The turnover frequency (TOF) value varies in the range of 3000 to 14 000 h−1 compared to 60 h−1 in the conventional stirred reactor. The space time yield (STY) or the overall reaction rate ranges from 650 to 4500 gprod. (gcat. h)−1, which is much larger than the value [ca. 19 gprod. (gcat. h)−1] for the conventional stirred reactor. To some extent, the present study has also demonstrated the concept of ‘Novel Process Windows’. [ABSTRACT FROM AUTHOR]