The kinetics of n-butane oxidation for the production of maleic anhydride (MA) over a commercial VPO catalyst has been investigated under aerobic and anaerobic conditions and at a temperature range of 400-435 degrees C. A kinetic model that can be applied under both aerobic and anaerobic conditions is presented. The model considers three types of oxygen: adsorbed oxygen, surface lattice oxygen and sub-surface lattice oxygen. Both adsorbed and surface lattice oxygen are considered active for the production of maleic anhydride and CO,. (c) 2006 Elsevier Ltd. All rights reserved.