Bubble dynamics and mass transfer enhancement in split–and–recombine (SAR) microreactor with rapid chemical reaction

•Bubble dynamics and gas-liquid mass transfer in the SAR microreactor were studied.•The bubble axial pulsation associated to SAR structure is analyzed.•The squeezing mechanism for parent bubble breakup is revealed.•The energy efficiency of the SAR microreactor is comparable to Corning AFR. In this study, a split–and–recombine (SAR) microreactor which is composed of convergent–divergent arc channel and rectangular obstacles was designed, and its enhancement characteristics in gas–liquid rapid chemical absorption system were explored. In the SAR microreactor, the deformation, splitting, stretching and breakup of bubbles are monitored by a high–speed camera. Accordingly, the bubble velocity pulsation caused by SAR structure is analyzed. The squeezing mechanism for bubble breakup located on the front surface of the obstacle is revealed. Two breakup patterns, namely complete and partial breakup, are observed, and the mass transfer performance is highly related to them. The mass transfer enhancement factor (Eka) of SAR structure increases with gas/liquid flow rate in complete breakup pattern while decreases in partial breakup pattern. The increase of gas–liquid flow rates and the number of SAR units, or slower reaction rate strengthens the velocity fluctuation and bubble breakup, resulting in an increase in Eka, with a maximum value of 2.74. Overall, the SAR microreactor performs comparable to Corning Advanced Flow Reactor in term of mass transfer energy efficiency. This work guides the application of SAR microreactor in rapid gas–liquid chemical reaction system.