Structural study of mesoporous titania and titanium stearic acid complex prepared from titanium alkoxide

A mesoporous titania was prepared from titanium tetraisopropoxide and stearic acid (STA). The pore size of the titania increases linearly from ca. 5 to 15 nm with increase in the STA/Ti ratio (X) for X < 1.5, while the change becomes negligible for X > 1.5. A mol equivalent of STA coordinates with Ti atom forming a bidentate carboxy group and excess STA forms propyl stearate. Upon calcination, the propyl stearate is removed at a lower temperature by vaporization, and does not affect the pore structure of the titania. The Ti-STA precursor has the layered structure of the Ti-STA complex, whose interplanar distance increases with increasing STA content, while the mesoporous titania is composed of aggregates of crystallites of anatase. During calcination of the precursor, decomposition of the complex and crystallization of anatase occur concurrently. The crystallization process is considered to be affected by the interplanar distance of the layered structure in the precursor, so that both the pore size and the pore volume increase with increase in the STA/Ti ratio.