Selective Oxidation and Ammoxidation Catalysis: Mechanism and Commercial Practice

Abstract

The mechanisms of the oxidation and ammoxidation of propylene over heterogeneous catalysts involve the chemisorption of propylene on Mo centers and formation of a radical-like Mo-complexed π-allylic intermediate viarate-determining H- abstraction by Bi-O. Subsequent O-insertion by the Mo=O moiety of a dioxo species forms a σ-O allyl complex, the acrolein precursor,. In ammoxidation analogous π-and σ-allyl species lead to acrylonitrile after activation of NH3via Mo=(NH) 2formation. Bi is also important in facilitating the conversion of the 0 and N σ-species via 1, 4-H shift to selective products.