Influence of preparation methods on properties of nanosized ZrO2/Al2O3 composite supports

The impregnation- precipitation method was adopted to prepare the nano-sized ZrO2/Al2O3 composite supports. The effects of impregnation and drying methods on the surface properties, thermal stability, and crystal structure of composite supports were characterized by X-ray diffraction, N-2 physical adsorption, differential scanning calorimetry (DSC), and temperature- programmed desorption. The results showed that there was no ZrO2-Al2O3 mixture or solid solution formed in the composite, and the nano-ZrO2 was only loaded on the surface of Al2O3. The specific surface area of ZrO2/Al2O3 dried under microwave (158.7 m(2) /g) was large with the most probable pore size of 19.4 nm, and the particle size of ZrO2 was about 4.2 nm with a tetragonal phase. Microwave induced the formation of new acid-base centers and enhanced the interaction between ZrO2 particles and Al2O3. The ZrO2/Al2O3 Composite support prepared by microwave drying had better thermal stability, and there was no absorption peak in the range of 873 - 1073 K in the DSC curves. The ZrO2/Al2O3 composite supports prepared by other methods have an obvious endothermic peak in the range of 903 - 1023 K, indicating that some of the tetragonal ZrO2 crystals on the composite support surface transformed into monoclinic ZrO2. Microwave drying could enhance the interaction between the nano-ZrO2 particles and Al2O3 Of the ZrO2/Al2O3 COMposite support prepared using the ultrasonic method and make the ZrO2 particle size (3.4 nm) smaller, without changing the crystal structure of ZrO2