J. R. Sohn, S. G. Cho, Y. I. Pae, and S. Hayashi
[Journal of Catalysis, Vol. 159, pp. 170-177, 1996]

Vanadium oxide-zirconia catalysts were prepared by dry impregnation of powdered Zr(OH)₄ with an aqueous solution of NH₄VO₃. The surface characterization of prepared catalysts was performed using FTIR, DSC, ⁵¹V solid state NMR, and XRD, and by the measurement of surface area. Figure 1 shows ⁵¹V NMR spectra. The addition of vanadium oxide up to 9 mol% to zirconia shifted the phase transitions of ZrO₂ from amorphous to tetragonal toward higher temperatures due to the interaction between vanadium oxide and zirconia. On the basis of the results of IR, XRD, and DSC, it is concluded that the content of V₂O₅ monolayer covering most of the available zirconia is 9 mol%, giving 2.3 V₂O₅ molecules/nm². Since the ZrO₂ dispersed vanadium oxide, the crystalline V₂O₅ was observed only with the samples containing V₂O₅ content exceeding the formation of a complete monolayer (9 mol%) on the surface of ZrO₂. For the samples calcined at 673 K, the acidity and surface area increase abruptly upon the addition of 0.2 mol% V₂O₅ to ZrO₂, and then both of them increase with increasing V₂O₅ content up to 5 mol%, showing the presence of Broested and Lewis acid sites on the V₂O₅/ZrO₂ catalyst.