Preparation and Characterization of Titania-Alumina Mixed Oxides with Hierarchically Macro-/Mesoporous Structures

A series of hierarchically macro-/mesoporous structured TiO2-Al2O3 mixed oxides with various molar ratios of Ti to Al was synthesized under different preparation conditions. The physical properties, that is, textural, morphological, and crystalline phase features of the prepared and calcined TiO2-Al2O3 materials were detailedly characterized by N-2 adsorption-desorption, scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermal analysis techniques. The results showed that the preparation conditions, such as the solution pH, the water concentration, the molar ratio of Ti to Al, and the surfactant, can greatly influence the sizes of macropores and mesopores, the specific surface area, the pore volume, and the crystallization process of the mixed oxides. Calcination treatments of the prepared materials revealed their high thermal stability. The 800 degrees C calcined samples were thermally stable and retained the hierarchically macro-/mesoporous structure. Compared with pure TiO2 and pure Al2O3, the presence of Al2O3 in the TiO2-Al2O3 mixed oxides retarded the anatase-to-rutile phase transformation, while the incorporation of TiO2 promoted the formation of the alpha-Al2O3 a. phase in the mixed oxides. The hierarchically structured porous TiO2-Al2O3 materials had high potential applications as catalyst supports.