Study of acidic and catalytic properties of sulfated zirconia prepared by sol-gel process: influence of preparation conditions

摘要

Two different processes were used in this study to prepare sulfated zirconia. The effect of both the hydrolysis ratio H_2O/Zr and S/Zr molar ratio were examined. Sample characterization was carried out using XRD, NH_3-TPD, N_2 adsorption-desorption and FT-IR spectroscopy using adsorbed probe-molecules (C_6H_6 and pyridine). Surface content before and after n-hexane isomerization reaction were emasured. We found that samples obtained by sol-gel process retain high amount of sulfur and exhibit important BET surface areas. The decrease of the hydrolysis ratio improves considerably acidic and catalytic properties. Lewis and Bronsted acid sites coexist but the Lewis ones are predominant. It was alos found that the increase of the Pt lowding in mechanical mixture of Pt/Al_2O_3 and sulfated zirconia enhances the catalytic activity and selectivity at moderate activation temperature.