Affiliation: | a Dipartimento di Chimica Industriale e dei Materiali, Viale Risorgimento 4, 40136, Bologna, Italy b INSTM, UdR, Bologna, Italy c EniTecnologie SpA, via Maritano 26, 20097, S. Donato, MI, Italy d Snamprogetti SpA, via Maritano 26, 20097, S. Donato, MI, Italy |
Abstract: | Rutile-type Cr/V/Sb mixed oxides, catalysts for the ammoxidation of propane to acrylonitrile, were prepared and characterized. For atomic ratios between components equal to Cr/V/Sb 1/x/1 and 1/x/2 the systems were monophasic, but different types of compounds formed depending on the ratio between the three metals. The compositional parameter which most affected the nature of the compound formed was the (Cr+V)/Sb atomic ratio. When this ratio was between 2 and ≈1, a rutile Cr3+/V4+/Sb5+ mixed oxide of composition Cr1VxSb1O4+2x developed (0<x<1), which in practice corresponds to a solid solution between 1 CrSbO4 and x VO2. When the (Cr+V)/Sb ratio was between 0.5 and ≈1, a rutile Cr3+/V3+/Sb3+/Sb5+ mixed oxide of composition CrVxSb1+x+2zO4+4x+4z developed (0<x<1), which corresponds to a solid solution between 1 Cr3+Sbz3+Sb1+z5+O4+4z and x VSbO4. The distinction between the two classes of compounds was not clear-cut, and when the (Cr+V)/Sb atomic ratio was around 1, mixed oxides containing both V3+ and V4+ formed. Values of the (Cr+V)/Sb atomic ratio lower than ≈0.5 led to the additional formation of antimony oxide. |