Support effect on the structure and reactivity of VSbO4 catalysts for propane ammoxidation to acrylonitrile

A new synthesis method for Sb-V-O based catalysts is proposed. VSbO4 phase is supported both in alumina and in niobia because it is known that such structure is the active phase for acrylonitrile formation. The relevance of the support on the structure and performance of the VSbO4 phase is evaluated by X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy and in the ammoxidation of propane to acrylonitrile. The role of segregated antimony oxide for the VSbO4 phase is confirmed in VSbO4/Al2O3. In this system, segregated antimony oxide is critical for the redox cycle of vanadium sites. However, a new catalytic phase forms in VSbO4/Nb2O5. Niobia support affords an efficient phase other than VSbO4 that is selective to acrylonitrile formation. This phase appears to be a Sb-promoted V-Nb-O one.