Characterization of Vanadium Oxide–Zirconia Catalyst

Vanadium oxide–zirconia catalysts were prepared by dryimpregnation of powdered Zr(OH)4with an aqueous solution ofNH4VO3. The surface characterization ofprepared catalystswas performed using FTIR, DSC,51V solid state NMR, and XRD,and by the measurement of surface area. The addition of vanadiumoxide up to 9 mol% to zirconia shifted the phase transitions ofZrO2from amorphous to tetragonal toward higher temperaturesdue to the interaction between vanadium oxide and zirconia. Onthe basis of results of IR, XRD, and DSC, it is concluded thatthe content of V2O5monolayer covering most of the availablezirconia is 9 mol%, giving 2.3 V2O5molecules/nm2. Sincethe ZrO2dispersed vanadium oxide, the crystalline V2O5wasobserved only with the samples containing V2O5contentexceeding the formation of complete monolayer (9 mol%) on thesurface of ZrO2. For the samples calcined at 673 K the acidityand surface area increase abruptly upon the addition of0.2 mol% V2O5to ZrO2, and then both of them increase withincreasing V2O5content up to 5 mol%, showing the presenceof Brønsted and Lewis acid sites on the V2O5/ZrO2catalyst.