Effect of the properties of hydrous zirconia prepared under various hydrothermal conditions on the isomerization activity of Pt/WO₃-ZrO₂

A series of hydrous zirconia samples were prepared by hydrothermal method and the effects of the properties of hydrous zirconia on the catalytic activity of Pt/WO₃-ZrO₂ in the hexane isomerization were investigated. The catalysts were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and differential thermal analysis (TDA), H₂-temperature programmed reduction (H₂-TPR) and NH₃-temperature programmed desorption (NH₃-TPD). The results showed that the hydrothermal treatment under different times and pH values led to remarkable changes in the properties (such as hydroxyl group, ordering degree and thermal stability) of hydrous zirconia. Moreover, the isomerization activity of Pt/WO₃-ZrO₂ varied distinctly with the hydrothermal treatment condition of hydrous zirconia. The correlation between the properties of hydrous zirconia and the isomerization activity of the catalyst was primarily established. It was proposed that the isomerization activity was strongly dependent on the stability and ordering degree of hydrous zirconia, while it was irrelevant to the amount of hydroxyl groups in hydrous zirconia.