Liquid-phase oxidation of cyclohexane with air in a microreactor: Kinetics and process intensification

The oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA oil) is a crucial liquid-phase reaction in industry. However, the conventional stirred-tank reactor and bubble column reactor suffer from poor heat and mass transfer performance, resulting in low efficiency and poor safety. In this work, a gas-liquid microreactor platform is constructed to intensify cyclohexane oxidation in a high-T,p new process window. A new reaction kinetic model is proposed and validated. The reaction rate constants and activation energy are determined under high-T,p conditions (160-200degree celsius, 2.5-4.5 MPa), which have been rarely involved in previous studies. Under the guidance of kinetic model, the impact of temperature, pressure, and the amount of oxygen on both reaction rate and product distribution are investigated. Furthermore, a two-zone temperature control strategy is suggested. A 5.5% conversion of cyclohexane with 85% selectivity towards desired products can be achieved at a residence time of 370 s.