Synthesis, characterization, and catalytic activity of SO4/Zr1−xSnxO2 Original Research Article

The Sn-doped zirconia catalysts, SO4/Zr1−xSnxO2 (x=0, 0.05, 0.10, 0.175, 0.25, 0.35), SO4/ZrO2, and SO4/SnO2, were prepared by hydroxide precipitation. The freeze-dried hydroxides were sulfated with (NH4)2SO4 and calcined at 500 °C for 3 h in O2. The X-ray powder diffraction (XRD) study show that the crystallinity of SO4/Zr1−xSnxO2 decreases with the incorporation of Sn. The BET surface areas of SO4/Zr1−xSnxO2 (x=0.05–0.35) range from 90 to 124 m2/g. SO4/ZrO2 has a surface area of 87 m2/g. The surface areas of SO4/SnO2 with 2.16 and 2.88 wt.% S are 152 and 101 m2/g, respectively. The FTIR photoacoustic spectrum of SO4/ZrO2 shows Brønsted acid site bands, whereas SO4/Zr1−xSnxO2 and SO4/SnO2 have both Brønsted and Lewis acid site bands. Temperature-programmed desorption of ammonia (NH3-TPD) results show that acid site distribution are similar for SO4/Zr1−xSnxO2 (x=0.05–0.35), but differ from those of SO4/ZrO2 and SO4/SnO2. Activities of these catalysts were examined for the benzoylation of anisole with benzoyl chloride and benzoic anhydride. The surface acidities and catalytic activities of SO4/Zr1−xSnxO2 were compared with those of SO4/ZrO2 and SO4/SnO2.