The two-fluid model was applied to simulate the hydrodynamics based on the process conditions in a cyclohexane oxidation airlift loop reactor (ALR). A lab-scale ALR was first investigated to validate the simulation methods and the simulated gas holdup and liquid velocity agree well with the experimental data. Following the validation, computational fluid dynamics (CFD) was then extended to study the industrial scale cyclohexane oxidation ALR. The CFD results indicate that the key hydrodynamic parameters for the circulation flow are the liquid circulation velocity and liquid circulation flux. The increasing liquid circulation flux in the downcomer enhances the downcomer gas holdup, while the increasing liquid circulation velocity in the riser reduces the riser gas holdup. The factor influencing the gas phase entrainment in the draft-tube is the liquid circulation flux rather than the liquid circulation velocity. With a constant reactor diameter, the gas holdup and liquid circulation flux increases with the increasing cross-sectional area ratio of downcomer to riser. The draft-tube with a horn-mouth can efficiently enhances the gas-liquid separation at the reactor top. Within a certain range, the axial position height of the draft-tube can influence the circulation driving force and resistance loss in the reactor. The results of this study are significant for guiding production, the optimization and scale-up study of this kind of reactors.(C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.