EFFECT OF THE TYPE OF PREPARATION ON THE PROPERTIES OF TITANIA SILICAS

Titania/silicas were prepared by four methods: (i) complexing-agent assisted sol-gel, (ii) coprecipitation, (iii) hydrogel kneading and (iv) xerogel kneading. The properties of these titania/silicas were investigated by thermal gravimetry and differential thermal analysis (TG-DTA), X-ray powder diffraction, solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), ammonia temperature programmed desorption (TPD) and nitrogen adsorption. Of the four methods, the complexing-agent assisted sol-gel method gave the most homogeneous titania/silicas. Their Ti-O-Si bond formation, acidities, and specific surface areas depended on complexing agents used in the preparations and the Ti/Si ratios of raw materials. In contrast, the kneading titania/silicas were heterogeneous and their properties did not depend on the Ti/Si ratio. The dependence of properties of coprecipitated titania/silicas on their Ti/Si ratio were intermediate between those of complexing-agent assisted sol-gel and kneading.