Dependences of catalyst layer thickness and pellet grading mode on partial oxidation of n-butane

•Industrial-scale reactor-pellet coupled model is successfully established.•Suitable catalyst layer thickness contributes to enhancing maleic anhydride yield.•Optimal pellet grading mode effectively mitigates hot spot temperatures.•Temperature sequence for improved maleic anhydride selectivity is proposed. An industrial-scale reactor-pellet coupled model incorporating realistic radial bed voidage is established for n-butane partial oxidation to maleic anhydride (MA) process. Simulation results demonstrate that the reactor packed with CLT-2.75 cylindrical pellets exhibits intense exothermic behavior at the front end of reactor, resulting in the over-oxidation of n-butane within the interior zone of the pellet. Although reducing the thickness of catalyst layers effectively mitigates heat release and prevents n-butane over-oxidation within the pellets’ interior zone, pellets with excessively thin catalyst layers would lead to lower n-butane conversion, making the reactor packed with CLT-0.825 pellets exhibiting improved MA selectivity and reduced hot spot temperature. The ultimate optimization of pellet grading with CLT-0.275/1.10 pellets indicates that implementing a temperature sequence characterized by lower temperature at the front end and higher temperature at the back end of the reactor could further notably reduce the hot spot temperature while maintaining a high MA yield.