Effects of Local Structural Changes of Orthorhombic Mo₃VO_<i>x</i> Induced by High-Temperature Heat Treatment on Catalytic Ammoxidation of Propane

The orthorhombic Mo3VOx (MoVO) crystal catalyst has a crystal structure analogous to that of the industrial catalyst for propane ammoxidation. However, it has been observed that MoVO exhibits poor selectivity for the formation of acrylonitrile (AN). Here, we found that a higher AN yield was attainable over the MoVO heat-treated at higher temperatures (600 °C) in a pure nitrogen stream. Structural analyses revealed that high-temperature heat treatment caused local structural changes through the migration and the segregation of VO2+ without altering the basic crystal structure of MoVO. This resulted in the change in the chemical formula from Mo30.66V11.34O114 to Mo30.66V7.22O104. The kinetic analysis revealed that the local structure after the segregation of VO2+ exhibited improved catalytic activity for the ammoxidation of propylene as the primary product for this reaction, resulting in a high AN yield in the propane ammoxidation. The obtained results offer a new insight into the catalytically active structure of the Mo–V-based mixed metal oxide for the ammoxidation of propane.