The n-butane selective oxidation has been studied in a membrane reactor, using high butane concentrations. Thanks to the oxygen distribution by the membrane, it is possible to keep the local composition outside the flammability zone. A MFI ceramic membrane was used to distribute oxygen (or part of it) in the catalyst bed, made of a VPO mixed oxide, either conventional or Co-doped. In a first step, the effect of the oxygen distribution has been studied, showing that, under standard reactant mixtures (O-2/butane = 12, low butane concentration), the membrane reactor performed very close to the conventional one. Under high butane concentrations, the VPO system suffered from a drastic decrease of the selectivity towards maleic anhydride (MA). The addition of cobalt to the VPO catalyst allowed keeping the MA selectivity at a high level (75%). The combination of the CoVPO catalyst and the MFI membrane was used to explore the membrane reactor performance with high butane concentrations in the feed, corresponding to the flammability zone in a conventional reactor. For these conditions, the MA productivity was three times higher than that observed with the conventional reactor. (c) 2005 Elsevier B.V. All rights reserved.