The oxidation of n-butane to maleic anhydride over an industrial vanadyl pyrophosphate oxide catalyst was investigated experimentally in millistructured reactors with varying slit widths to investigate the process intensification potential of this reaction. Although the smaller reactor behaved isothermally, even in the presence of high n-butane concentrations, moderate hot spots never exceeding more than 15K above the salt bath temperature occurred in the larger catalyst channel. After exposure to high n-butane concentrations, a certain amount of catalyst deactivation was observed, which could be partly restored through reoxidation with pure oxygen. The reactor-specific maleic anhydride productivities obtained are much larger than those in conventional multitubular reactors.