Characterization and catalytic performance of Au/Ti-HMS catalysts on the oxidative desulphurization using in situ H2O2: Effect of method catalysts preparation

Au/Ti-HMS was prepared by in situ method, NH₃ deposition–precipitation (NH₃ DP) and urea deposition–precipitation (Urea DP), respectively. The catalysts were characterized by a series of techniques including ICP, powder XRD, N₂ sorption, UV–visible spectroscopy, TEM and H₂-TPR. Using n-octane containing BT, DBT and 4,6-DMDBT as model compound, the performance of the catalysts in oxidative desulfurization (ODS) using in situ generated H₂O₂ from H₂ and O₂ were investigated. The results show that preparation method influences porous structure of the support and gold particles size. In situ sample has maintained the intrinsic structure of Ti-HMS, whereas, the gold particles are not as uniform and small as that of DP sample. NH₃ DP sample still possesses the wormhole structure of HMS despite the absence of typical XRD peak. The mesoporous structure of urea DP sample has been damaged seriously. Au³⁺ on outer surface of the support is easier to be reduced than that in pores, as confirmed by H₂-TPR. In addition, the three samples exhibit different catalytic activities in ODS using in situ H₂O₂ as oxidant. For the removal of BT and DBT, Au/Ti-HMS (NH₃ DP) exhibits the highest catalytic activities. Regarding the removal of 4,6-DMDBT, the optimum catalyst is Au/Ti-HMS (In situ); however, Au/Ti-HMS (Urea DP) nearly loses catalytic activity.