In order to address the uneven flow velocity of catalytic reactors and to solve problems such as wear and soaring temperatures in catalysts, a three-dimensional mathematical model of a catalytic reactor was established. A comparison of the physical model and the simulation results revealed that the experimental results were a good fit to the mathematic model. The optimization results revealed the following: advantageous placement of the catalyst was 12.5-17.5 mm from the optimization site; the cross plate + porous plate was preferential; and the area-weighted uniformity index reached 0.93. When the catalyst was placed 25-30 mm from the optimization site, the cross plate + strip plate + hole or cross + grid + plate was preferential and the area-weighted uniformity index reached 0.93. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.