The oxidation of butane to maleic anhydride in a new reactor is described. This reactor is a two-zone fluidized bed, where butane and oxygen are fed at different levels, providing separated zones for catalyst oxidation and for butane reaction/catalyst reduction. The solid mixing characteristic of fluidized beds provides the circulation of solid, in such way that the fed oxygen enters to the reducing zone as part of the solid structure; thus, the butane reacts with lattice oxygen in the catalyst. The effect of some operating variables on conversion and selectivity is described. High yields to maleic anhydride may be achieved by means of this operation system. The oxygen and butane concentrations at a point below the butane entry are also reported. This is to ensure the operation is outside flammability limits and to quantify the backmixing of the gas in the bed. Therefore, this system allows feeding butane concentrations higher than those industrially employed in fixed bed reactors but avoids the formation of explosive mixtures. The yield to maleic anhydride obtained with high butane concentrations is similar to that in other reactors where the catalyst operates in reduction-oxidation cycles but avoids an unsteady-state operation or the use of a circulating fluidized bed.