Maleic anhydride (MSA) is produced by the selective catalytic oxidation of butane on vanadium phosphorus oxide (VPO) catalysts. The heat of reaction released in the industrial process leads to the formation of pronounced hotspots and the associated risks with regard to the stability and safety of the process. In addition, the activity of the VPO catalyst changes depending on the reaction conditions. Precise control of the reaction process is therefore essential for safe operation of the reactor. Industrially, very small quantities of suitable phosphorus compounds are used for this purpose, which have a dampening effect on the catalyst activity.