Active Sites on Molybdate Surfaces, Mechanistic Considerations for Selective Oxidation, and Ammoxidation of Propene

Abstract

Molybdates involving various metal additives play a dominant role in such industrially important catalytic processes as selective oxidation (propene to acrolein) and ammoxidation (propene to acrylonitrile); however, the details of the reaction mechanism and of the surface sites responsible are yet quite uncertain. In order to establish the thermochemistry and detailed mechanistic steps involved with such reactions, we have performed ab initio quantum chemical calculations [generalized valence bond (GVB) and configuration interaction (CI)]. These studies indicate a special importance of multiple surface dioxo Mo sites (possessing two Mo-O double bonds and hence spectator oxo groups) arranged together so as to provide the means for promoting the sequence of transformations.