Influence Of The Formation Of Aluminum Spinel, Alvo4, On The Catalytic Activity Of V2o5 Supported On Gamma-Alumina

Vanadium pentoxide catalysts supported on gamma-alumina (1 - 50 mole %) were prepared by impregnation method and calcined at 400 and 680 degrees C for 4 h. The structure of the original and calcined samples was characterized by DTA and X-ray diffraction. The electrical conductivity measurements of the calcined samples reveal that the conductance increases while the Fermi potential decreases on increasing V2O5 content up to 50 mole %. The catalytic dehydration of isopropanol was carried out at 250 degrees C using a flow system. The results showed an observable increase in the extent of catalytic dehydration of the alcohol on increasing V2O5 content from 5 mole % to 50 mole % with the samples calcined at 400 degrees C, The catalysts calcined at 680 degrees C were found to exhibit maximum activity at the composition of 20 mole % V2O5. Above the maximum a sharp decrease in the conversion and the yield towards propylene was found due to formation of aluminium vanadate, i.e. AlVO4 spinel. The low activity associated with the existence of this spinel was correlated with the sharp decrease in the Fermi potential.