Synthesis, characterization, and catalytic activity of SO 4/Zr 1− xSn xO 2

Abstract

The Sn-doped zirconia catalysts, SO 4/Zr 1− x Sn x O 2 ( x=0, 0.05, 0.10, 0.175, 0.25, 0.35), SO 4/ZrO 2, and SO 4/SnO 2, were prepared by hydroxide precipitation. The freeze-dried hydroxides were sulfated with (NH 4) 2SO 4 and calcined at 500 °C for 3 h in O 2. The X-ray powder diffraction (XRD) study show that the crystallinity of SO 4/Zr 1− x Sn x O 2 decreases with the incorporation of Sn. The BET surface areas of SO 4/Zr 1− x Sn x O 2 ( x=0.05–0.35) range from 90 to 124 m 2/g. SO 4/ZrO 2 has a surface area of 87 m 2/g. The surface areas of SO 4/SnO 2 with 2.16 and 2.88 wt.% S are 152 and 101 m 2/g, respectively. The FTIR photoacoustic spectrum of SO 4/ZrO 2 shows Brønsted acid site bands, whereas SO 4/Zr 1− x Sn x O 2 and SO 4/SnO 2 have both Brønsted and Lewis acid site bands. Temperature-programmed desorption of ammonia (NH 3-TPD) results show that acid site distribution are similar for SO 4/Zr 1− x Sn x O 2 ( x=0.05–0.35), but differ from those of SO 4/ZrO 2 and SO 4/SnO 2. Activities of these catalysts were examined for the benzoylation of anisole with benzoyl chloride and benzoic anhydride. The surface acidities and catalytic activities of SO 4/Zr 1− x Sn x O 2 were compared with those of SO 4/ZrO 2 and SO 4/SnO 2.