We noticed a gradual decrease in th

We noticed a gradual decrease in the intensity of the IR band at high frequency, corresponding to the most basic hydroxyl groups of the Al–Zr support, with increase in vanadia loading. This was due to the preferential reaction of active vanadia species with the basic hydroxyl groups of the support. In the present investigation also, a gradual decrease in the intensity of the IR vibration at 3603 cm−1 could be seen, with increase in V2O5 content suggesting consumption of the most basic hydroxyl groups of the Ti–Zr support with the active component. Eberhardt et al. [25] in their IR studies on V/Al2O3 catalysts have shown that the most basic surface hydroxyl groups exhibit high IR frequency and sequential consumption of hydroxyl groups of the alumina support with vanadia starting with the most basic –OH groups of the support.