(394e) Probing the Mechanism of Propane Ammoxidation Over Mo-V-Te-Nb-O Catalyst – Insights From First-Principles Calculations

Kaliappan, M., University of Cincinnati
Yu, J., University of Cincinnati
Xu, Y., Oak Ridge National Laboratory
Guliants, V. V., University of Cincinnati

The crystalline M1 phase of the Mo-V-Te-Nb-O mixed metal oxide possesses the unique ability to convert propane directly into acrylonitrile. This process consists of a series of steps involving propane, ammonia and O2 activation, oxidative dehydrogenation (ODH), and N-insertion. However, the detailed mechanism remains poorly understood despite a great deal of research on this complex catalytic system, which hinders further improvement of acrylonitrile selectivity required for practical applications. To shed light on this topic, we have performed density functional theory (DFT) calculations to explore the reaction pathways for propane ammoxidation on cluster models of the proposed active and selective site present in the surface ab plane of the M1 phase. Our earlier results showed that Te oxo may play an important role in initial H abstraction from propane, and that the adsorption energies of surface intermediates were strongly dependent on the number of ab planes in the cluster, indicating the need to employ multilayer cluster models to correctly account for the energetics of surface chemistry on this mixed metal oxide catalyst. In this talk, we present our results that provide mechanistic insights into the activation of propane to a π-allyllic intermediate via ODH steps and elucidate catalytic roles of the different surface metal cations in successive hydrogen abstraction steps.