−− The aim of this work was to model the catalytic oxidation of n-butane and butenes (Raffinate II) mixture to maleic anhydride (MAN) over a vanadium-phosphorus oxide (VPO) catalyst in a fluidized bed reactor (FBR). The three phase Kunni–Levenspiel hydrodynamic model (K-L) was used to describe the reactor. The obtained differential equations were solved by the fourth order Runge–Kutta numeric method. The K-L model was validated by a fitting comparison with reported experimental data for MAN production from nbutane. For the n-butane and Raffinate mixture, the maximum calculated MAN yield was about 52% over the FBR emulsion with a 49% of Raffinate conversion, and 51% of MAN selectivity. As a conclusion, the simulation program demonstrated a suitable performance to predict MAN selectivity, reactants conversion, and MAN and reactants concentration profiles. Keywords−− Maleic Anhydride, Fluidized Bed Reactor, n-butane, Raffinate II.