Modeling the selective oxidation of n-butane to maleic anhydride: From active site to industrial reactor

Abstract

In this contribution to the Special Issue honoring 100 very successful years of Casale S.A., we review and critically discuss the current status of modeling the most demanding selective partial oxidation reaction industrially applied: the partial oxidation of n-butane to maleic anhydride. We examine theoretical model descriptions of this partial oxidation reaction covering all relevant length scales: from modeling the active site and elementary steps, microkinetic and macrokinetic models, to reactor models on all length scales from laboratory reactors up to industrial-size production reactors. We also include in our manuscript the latest CFD developments aiming at a better understanding of heat and mass transfer in industrial catalyst beds as well as effects of the local bed structure. The contribution also covers relevant experimental findings with respect to the catalytically active species or sites on the catalyst surface, the reaction mechanism as well as microkinetic considerations. 60 years of research have greatly improved our understanding of the selective partial oxidation reaction. However, a critical review of the different aspects of the n-butane oxidation and its industrially used catalyst reveals on all length scales that there still remain unanswered questions, and that there are still some inconsistencies in our fundamental understanding. This situation arises from the fact that the catalyst for n-butane partial oxidation is a highly complex and dynamic system and its performance depends on all details of its generation and its operational history.