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

An industrial-scale reactor-pellet coupled model incorporating realistic radial bed voidage is established for nbutane 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.