Propane ammoxidation over Mo-V-Te-Nb-O M1 phase: Density functional theory study of propane oxidative dehydrogenation steps

Document Type

Article

Publication Date

1-1-2014

Abstract

Propane ammoxidation to acrylonitrile catalyzed by the bulk Mo-V-Te-Nb oxides has received considerable attention because it is more environmentally benign than the current process of propylene ammoxidation and relies on a more abundant feedstock. This process is proposed to consist of a series of elementary steps including propane oxidative dehydrogenation (ODH), ammonia and O2 activation, NHx insertion into C3 surface intermediates, etc. Density functional theory calculations were performed here to investigate the three sequential H abstraction steps that successively convert propane into isopropyl, propene, and π-allyl on cation sites in the proposed selective and active center present in the ab plane of the Mo-V-Te-Nb-O M1 phase. The initial H abstraction from propane was found to be the rate-limiting step of this process, consistent with both the proposed reaction mechanism for propane ammoxidation on the Mo-V-Te-Nb oxides and current understanding of V5+ as the active site for alkane activation on V-based oxides. Te=O was found to be significantly more active than V5+=O for the H abstraction from propane, which suggests that the surface and bulk Te species may be different. The role of Mo=O is most likely limited to being an H acceptor from isopropyl to form propene under ammoxidation conditions.

Publication Source (Journal or Book title)

Catalysis Today

First Page

28

Last Page

34

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