Modeling the dynamic behavior of industrial fixed bed reactors for the manufacture of maleic anhydride

- Detailed model for oxidation of n-butane in fixed bed reactors is proposed.
- Moderating effect of phosphorus on the n-butane oxidation is described.
- Kinetic model combined with activity model accounting for this phosphorus dynamics.
- Various interactions between phosphorus and water included.
- Model successfully applied to fixed bed pilot reactor experiments over 500 h.

The industrially important selective oxidation of n-butane over vanadium phosphorus oxide catalysts in fixed bed reactors is affected by phosphorus induced dynamic changes of the catalyst activity. An economic process management therefore requires an adequate control of the operating conditions including the precise addition of a phosphorus containing compound in the ppm range. In a previous work (Lesser et al., 2016) we experimentally investigated these phenomena and related our findings to the diverse literature discussions abound reaction mechanism and active sites. Based on our conclusions, the present work provides a detailed model for the phosphorus dynamics which is connected to a two-dimensional heterogeneous reactor model. The model is able to describe the reactor behavior properly over 500 h time on stream including many variations of the operating conditions. The dynamically changing activity profiles reflect the evolution of temperature profiles and product compositions with only minor deviations.