ACTIVITIES OF VANADIUM-OXIDES IN AMMOXIDATION OF 3-PICOLINE

Ammoxidation of 3-picoline to nicotinonitrile was studied on V2O5, V6O13, and V2O4 catalysts in a fixed-bed integral reactor. The activity studies showed that V6O13 was the most active and selective catalyst of the pure oxides, with a maximum yield of 76% nicotinonitrile at 365 °C. The maximum yield on V2O5 catalyst was 34%, and was obtained at a higher temperature, 458 °C. V2O4 was found to be inactive under the conditions studied. The activities and selectivities of the oxides changed rapidly with reaction time when V6O13 and V2O4 were studied. By means of X-ray diffraction and a titrimetric method, the average oxidation number of vanadium was determined, V6O13 was both oxidized and reduced during the reaction; V2O4 was oxidized, while a relatively smaller reduction of V2O5 could be detected. The experiments showed that the V6O13 catalyst used, with both V2O5 and V6O13 phases present, was more selective than any of the pure oxides. This may be explained by active boundary surfaces. Also a mechanism of formation of nicotinonitrile is proposed, which includes a step in which an adsorbed aldehyde complex reacts with ammonia. © 1979.