DEPENDENCE OF THE CATALYTIC BEHAVIOR OF V-SB-OXIDES IN PROPANE AMMOXIDATION TO ACRYLONITRILE FROM THE METHOD OF PREPARATION

The catalytic behavior in propane ammoxidation to acrylonitrile of V-S b-oxides prepared by four different methods and with a Sb : V ratio in the 0.8-3.0 range was studied and analyzed in relation to the structu ral/composition features of these samples determined by XRD, IR and SE M-EDX techniques. In particular, the following aspects are discussed: (i) composition, (ii) local homogeneity and morphology of the samples, () presence, amount and dimensions of crystalline phases, (iv) presen ce and nature of the amorphous phases, and (v) crystallographic and no n-stoichiometric features of the approximate to VSbO4 phase. It is sug gested that the selective behavior in propane ammoxidation is related principally to the nonstoichiometry of the approximate to VSbO4 phase and especially the creation of a Sb-rich approximate to VSbO4 phase, t he formation of which depends on the microstructure of the catalyst, c hemistry of preparation and Sb : V ratio. (C) 1997 Elsevier Science B. V.