Mechanism and kinetics of the aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin in a membrane microchannel reactor

• Qi Han^a
• Xian-Tai Zhou^a
• Xiao-Qi He^d
• Hong-Bing Ji^{b, c}

• ^aFine Chemical Industry Research Institute, School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China
• ^bFine Chemical Industry Research Institute, School of Chemistry, Sun Yat -sen University, Guangzhou 510275, China
• ^cSchool of Chemical Engineering, Guangdong University of Petrochemical Technology, Maoming 525000, China
• ^dHuizhou Research Institute, Sun Yat-sen University, Huizhou 516081, China

The highly efficient selective aerobic oxidation of benzyl alcohol to benzaldehyde catalyzed by cobalt porphyrin was achieved in a membrane microchannel reactor. The efficiency of benzyl alcohol oxidation was remarkably improved in the micro-structured chemical system, achieving a conversion and benzaldehyde selectivity of 82% and 98%, respectively, in 6.5 min. The classification and transfer of free radicals, as well as the oxygen-transfer mechanism, were determined by in situ EPR (electron paramagnetic resonance) and in situ UV–visible spectroscopy. Further kinetic studies revealed that the oxidation of benzyl alcohol follows the Michaelis–Menten kinetics, with Km = 0.133 mol/L.A mathematic kinetic model was proposed, and the kinetic model fitted the experimental data well. The mathematical model can predict the reaction process at a wide range of benzyl alcohol concentrations, which is beneficial for the process optimization and reactor design.

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