Bubble size distribution, gas holdup, and mass transfer in tubular membrane reactor: Effect of membrane wettability

In this work, three types of tubular membrane were prepared and characterized: hydrophilic, Janus, and hydrophobic. In the MDEA/water-N₂ system, the hydrophilic membrane tube generates the smallest bubble size (161–256 μm) with narrow distribution and hydrophobic membrane tube produces the largest bubble size (3378–4357 μm) with a broader distribution, while the Janus membrane tube yields bubbles with an average size ranging from 668 to 927 μm. For the ethanol-N₂ system, the differences in bubble size among the different membrane tubes are less pronounced. The hydrophilic, hydrophobic, and Janus membrane tube produces bubbles size of 300–477 μm, 376–633 μm, and 413–697 μm, respectively. The bubble size distribution for three types of membrane tube follows a Rosin-Rammler (R-R) distribution. A gas holdup of 4–35.3% and gas–liquid interfacial area of 91–8859 m²/m³ can be obtained for three types of membrane tubes. Based on 0.2 mol/L MDEA-CO₂ mass transfer system, Janus membrane shows the superior mass transfer coefficient performance due to the appropriate bubble size and narrow bubble size distribution. Predictive models for average bubble size, gas holdup, and gas–liquid mass transfer coefficient of three types of membrane tube were developed, showing good agreement with measured values.