Abstract: 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 byX-raydiffraction, N2 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 m2/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 873-1073K in the DSC curves. The ZrO2/Al2O3 composite supports prepared by other methods have an obvious endothermic peak in the range of 903-1023K, 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.

Key words: nano-material, zirconia, alumina, composite support, microwave drying