Effect of preparation methods on properties of alumina/titanias

Alumina/titanias have been prepared by three methods: complexing-agent-assisted sol–gel; coprecipitation; and hydrogel kneading. The relationship between the preparation methods and the properties of the alumina/titanias was investigated by thermal gravimetry and differential thermal analysis (TG–DTA), X-ray powder diffraction, laser Raman spectroscopy, solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), ammonia temperature-programmed desorption (TPD) and nitrogen adsorption. Of the three preparation methods, the complexing-agent-assisted sol–gel method gave the most homogeneous alumina/titanias, and their acidities and specific surface areas depended on complexing agents used in the preparation and the Ti:Al ratios of the raw materials. In contrast, kneading alumina/titanias were relatively heterogeneous and their properties did not depend on the Ti:Al ratio. Regarding the dependences of properties of alumina/titanias on the Ti:Al ratio, coprecipitation alumina/titanias are intermediate between complexing-agent-assisted sol–gel and kneading ones.