Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

• Published in: Chinese journal of chemical engineering Vol. 55; no. 3; pp. 84 - 92
• Main Authors: Han, Qi, Zhang, Xin-Yuan, Wu, Hai-Bo, Zhou, Xian-Tai, Ji, Hong-Bing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-03-2023; Fine Chemical Industry Research Institute,School of Chemical Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,China%Huizhou Research Institute,Sun Yat-sen University,Huizhou 516081,China%Fine Chemical Industry Research Institute,School of Chemical Engineering and Technology,Sun Yat-sen University,Zhuhai 519082,China; Huizhou Research Institute,Sun Yat-sen University,Huizhou 516081,China%Fine Chemical Industry Research Institute,School of Chemistry,Sun Yat-sen University,Guangzhou 510275,China
• Subjects: Benzyl alcohol; Bubble column reactor; Computational fluid dynamics (CFD); Gas–liquid flow; Mass transfer; Membrane microchannel reactor; Membrane microchannel reactor; Gas–liquid flow; Bubble column reactor; Benzyl alcohol; Mass transfer; Computational fluid dynamics (CFD); Computational fluid dynamics(CFD); Gas-liquid flow
• ISSN: 1004-9541; 2210-321X
• DOI: 10.1016/j.cjche.2022.05.020

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The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated (CoTPP: cobalt (II) meso-tetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel (MMC) reactor and a bubble column (BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor, and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup (2.9 times higher than that of BC reactor), liquid film mass transfer coefficient (8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area (3.8 times higher than that of BC reactor). Moreover, the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.