Mesoporous Titania Prepared in the Presence of Alkylamine.

Abstract

Mesoporous titania with high specific surface area was prepared by the hydration and condensation of titanium tetraisopropoxide (TTIP) in presence of alkylamine, which was used as a ligand-assisted template. The peak in the lower angle region of XRD patterns for as-synthesized titania powder was observed. This pattern of XRD suggests that the powder has an ordered nanostructure. The preparing method to obtain the sharp XRD pattern of as-synthesized powder is as follows; The precipitates, which were obtained by adding the distilled water without pH control to the mixing solution of the 2:1 TTIP to alkylamine molar ratio, were aged for 7 days at 25°C. The d(100)-spacing value is linearly increased with the alkyl chain length of alkylamine. The slope of the correlation line is larger than that in MCM-41, which has a hexagonally packed array of noninterconnecting cylindrical pores. The d-spacing value of the ordered nanostructure in MCM-41 is greatly increased by the addition of mesitylene, but the d(100)-spacing of the prepared titania in this study is slightly increased with the mesitylene concentration. These results may be caused by the difference in the ordered structure. It is presumed that the ordered nanostructure of the titania is a lamellar structure, but the nanostructure can not be confirmed by the other measurements. The surfactants in titania were removed by calcination and solvent extraction methods. The ordered nanostructure was destroyed by the removing surfactants. The BET specific surface area of the titania powder, in which the surfactants was removed with solvent extraction, is much larger than that with calcination. The specific surface area and pore volume increase with the addition of mesitylene and the largest surface area is 688 m2/g.