Effect of Fe, Ga, Ti and Nb substitution in ≈SbVO 4 for propane ammoxidation

Abstract

Substitution in rutile-type ≈SbVO 4 was made with Fe 3+ and Ga 3+ replacing V 3+, and Nb 5+ replacing Sb 5+. Moreover, preparations with Ti were synthesised where Ti 4+ ions substitute for both V 4+ and V 3+/Sb 5+ pairs. ≈SbVO 4-related phases containing Ti together with Fe and Ga were also prepared. The samples were characterised using X-ray diffraction, DRIFT and Raman spectroscopy. The characterisations show the formation of a cation deficient single rutile-type phase. Use of the samples in propane ammoxidation to produce acrylonitrile reveals, compared with the pure ≈SbVO 4 phase, that Fe, Ga and Ti substitution in ≈SbVO 4 results in lower activity but considerably higher selectivity to acrylonitrile at the same level of propane conversion. Niobium substitution, on the contrary, gives no improved catalytic properties. Correlations are presented between the catalytic and structural properties of the catalysts. It is demonstrated that isolation in the structure of the propane activating V–O . sites in a surrounding of nitrogen inserting Sb-sites results in improved selectivity for acrylonitrile formation.