The dynamic nature of vanadyl pyrophosphate, catalyst for the selective oxidation of n-butane to maleic anhydride

The reactivity of vanadyl pyrophosphate (VO)2P2O7, catalyst for n-butane oxidation to maleic anhydride, was investigated under steady and unsteady conditions, in order to obtain information on the status of the active surface in reaction conditions. Specific treatments of hydrolysis and oxidation were applied in order to modify the characteristics of the surface layer of the catalyst, and then the unsteady catalytic performance was followed along with the reaction time, until the steady original behavior was restored. It was found that the transformations occurring on the vanadyl pyrophosphate surface depend on the catalyst characteristics (i.e., on the P/V atomic ratio) and on the reaction conditions.