Characterization of SO4 2−/TiO2 and its catalytic activity in the epoxidation reaction

The solid acid catalysts SO 4 2− /TiO 2 were prepared by the impregnation technique under two preparation conditions which were different in calcination temperature and concentration of impregnation solution of H 2 SO 4 . The characterization was carried out by using Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), temperature programmed desorption of NH 3 (NH 3 -TPD), N 2 -BET, X-ray fluorescence and thermal gravity (TG)–differential scanning calorimetry (DSC). The characteristic peaks in the FTIR spectrum were essentially the same within the calcination temperature range of 400–600 °C. The XRD results indicated that the sample could show partial specific peaks of the anatase phase as the calcination temperature was higher than 400 °C. The obvious strong acid and superacid sites of the prepared SO 4 2− /TiO 2 were conformed by the NH 3 -TPD results. The BET surface areas of 102–206 m 2 /g were measured by the N 2 -BET method, and the pore size distributions were essentially mesoporous. The TG–DSC results showed that SO 4 2− /TiO 2 would decompose at about 500 °C in the air. The solid acid SO 4 2− /TiO 2 were used for the epoxidation of castor oil. The lowest iodine value of the product was 52.65/100 g when the reaction temperature was 65 °C, reaction time was 10 h and catalyst loading was 15 wt.%.