The effect of the preparation procedure on thermal phase transitions in zirconium oxide modified by sulfate ions

The thermal properties and phase transitions of zirconium oxides modified by sulfate ions were studied by the thermogravimetry, X-ray diffraction, and low-temperature krypton adsorption methods. The strength of bonds between sulfate groups and the surface of zirconium oxide and the number of surface sulfate groups were shown to depend on the preparation procedure. Modification of amorphous zirconium hydroxide Save samples with 0.8 mg/m(2) of SO4 groups, whereas the content of sulfate groups in crystalline samples was 0.3 mg/m(2) Samples prepared from amorphous zirconium hydroxide and crystalline ZrO2 were thermally stable up to 820 and 920 K, respectively. Sulfate groups were found to influence thermal phase transitions and the specific surface of modified zirconium hydroxide. Recommendations on the use of these samples as catalysts are given.