CHARACTERIZATION OF VANADIUM OXIDE-ZIRCONIA CATALYST

Vanadium oxide-zirconia catalysts were prepared by dry impregnation of powdered Zr(OH)(4) with an aqueous solution of NH4VO3. The surface ch aracterization of prepared catalysts was performed using FTIR, DSC, V- 51 solid state NMR, and XRD, and by the measurement of surface area. T he addition of vanadium oxide up to 9 mol% to zirconia shifted the pha se transitions of ZrO2 from amorphous to tetragonal toward higher temp eratures due to the interaction between vanadium oxide and zirconia. O n the basis of results of IR, XRD, and DSC, it is concluded that the c ontent of V2O5 monolayer covering most of the available zirconia is 9 mol%, giving 2.3 V2O5 molecules/nm(2). Since the ZyO(2) dispersed vana dium oxide, the crystalline V2O5 was observed only with the samples co ntaining V2O5 content exceeding the formation of complete monolayer (9 mol%) on the surface of ZrO2. For the samples calcined at 673 K the a cidity and surface area increase abruptly upon the addition of 0.2 mol % V2O5 to ZrO2, and then both of them increase with increasing V2O5 co ntent up to 5 mol%, showing the presence of Bronsted and Lewis acid si tes on the V2O5/ZrO2 catalyst. (C) 1996 Academic Press, Inc.