Influence of preparation method on the properties of V-Sb-O catalysts for the ammoxidation of propane

Abstract

The characteristics of V-Sb-O catalysts for the ammoxidation of propane prepared according tothe different procedures reported in patents and open literature (solid state reaction, redox reaction in solution, sol-gel preparation and coprecipitation methods) as a function of the Sb:V ratio, heat treatment and changes during catalytic reaction are discussed. Results show the influence of the preparation method on the final characteristics of the catlayst due to the competition between the formation of the VSbO4 rutile-like phase and oxidation of vanadium to form V5+-microdomains. During the catalytic reaction the V5+-oxide reduces to form an intergrown rutile-like V2O4 phase, but depending on the preparation method the V-oxide may not be accessible to the gaseous reactants. It is also shown that Sb5+-oxide on the surface of vanadium-antimonate is active in the synthesis of acrylonitrile and that vanadium catalyzes the reoxidation of antimony, as well as plays other roles in the mechanism of oxidative dehydrogenation of propane to propylene and in the side reaction of ammonia oxidation to N2.