Effect of vanadium modification on structure and catalytic properties of SO42-/ZrO2-Al2O3 solid acid catalyst

The V-promoted SO42-/ZrO2-Al2O3 solid superacid catalyst was prepared by the coprecipitation and impregnation method under different conditions. The catalytic properties of the samples were evaluated through esterification of acetic acid and n-butanol and characterized by thermogravimetry (TG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area measurement, and X-ray photoelectron spectroscopy (XPS). The results show that among all the prepared samples the one that was calcined at 600 degrees C, aged at 0 degrees C, and impregnated with a solution containing 0.005 mol/l, NH4VO3 after impregnation with sulfuric acid has the highest esterification rate of 99.71% For this sample there was no significant change in the catalytic activity after being recycled 5 times (averaged 98.59%). An analysis of XRD patterns reveals that the incorporation of vanadium into tetragonal zirconia stabilizes the compound, the aging facilitates the formation of tetragonal zirconia microcrystals, and the calcination increases the reactivity of the catalyst. by producing a greater fraction of active tetragonal zirconia with a larger surface area. It can be seen from the FT-IR spectra that superacid structures are formed in the Catalysts and the absorption peak for the S=O bond is strengthened remarkably. The XPS results indicate that there are strong interactions between the V(V) ions and their surroundings. The TG plots show that the samples aged at 0 degrees C exhibited less stability in despite of better catalytic activity.