Synthesis of acrylonitrile from propane on V-Sb-based mixed oxides

The catalytic behavior of propane ammoxidn. to acrylonitrile of pure VSbO4 + Sb2O4 (VSbO) samples (V:Sb at. ratio in the range 0.2-1), of modified VSbO samples with Al2O3, TiO2 or SiO2 and of further promoted systems with W or Mo is analyzed. V-Sb-Al2O3 based systems show an interesting potential for the development of a new process of acrylonitrile formation directly from propane. Al-oxide does not act merely as a support for the VSbO phase, but has a specific structural effect and greatly promotes the formation of propylene from propane. Catalytic and characterization results suggest that the active phase in propane ammoxidn. is not a pure VSbO4 rutile phase plus Sb2O4, but rather an amorphous VSbO4/Sb2O4 system epitaxially intergrown with AlSbO4 rutile phase whose formation is catalyzed by the presence of V. This system may be further promoted by the addn. of W or Mo. Kinetic anal. of the propane ammoxidn. shows that acrylonitrile forms by two parallel pathways, one directly from propane and the second through the intermediate formation of propylene, the latter being the prevalent path. In all cases propylene is the main reaction product obsd., esp. at low conversion, with selectivities up to about 80%. [on SciFinder(R)]