Preparation, characterisation and catalytic evaluation of MgF2 supported V2O5 catalysts for ammoxidation of 3-picoline Original Research Article

Non-conventional MgF2 supported V2O5 catalysts with different vanadia contents (2–15 wt.%) were prepared by impregnation (using NH4VO3), characterised and catalytically evaluated for selective ammoxidation of 3-picoline to nicotinonitrile. Oxygen and ammonia chemisorption uptakes increased continuously from 60 to over 600 μmol g−1 and 275 to >750 μmol g−1, respectively, with rise in V2O5 proportion indicating that the redox as well as acidic sites are increasing with increase in V2O5 content. Thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) analysis revealed endothermic as well as exothermic thermal effects mainly due to liberation of water and ammonia, and also due to structural changes. XRD patterns showed the formation of crystalline V2O5 in the fresh solids having 8 wt.% V2O5 and above and NH4VO3 phase in the spent samples. The conversion of 3-picoline is observed to increase continuously with increase in V2O5 loading. However, the selectivity of nicotinonitrile is found to be independent on conversion of 3-picoline. The catalyst with the highest V2O5 loading (15.7 wt.%) displayed the best activity (X > 90%) and selectivity (S > 95%) compared to all other catalysts of this series. The 3-picoline conversion of 10% at 548 K is increased to almost 100% with rise in temperature to 663 K. Increase in 3-picoline feed rate and NH3: 3-picoline ratio exhibited an inhibiting effect on the conversion, while an increase in air: 3-picoline ratio has no significant influence on the performance.