Investigation on the delaminated-pillared structure of TiO2-PILC synthesized by TiCl4 hydrolysis method

Abstract

TiO2-PILCs were synthesized by the reaction between montmorillonite and acidic solutions of hydrolyzed TiCl4. Unlike commonly reported microporous pillared structure, a meso-microporous delaminated structure containing pillared fragments was observed in the resulting TiO2-PILC, based on the combined analyses of powder X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, chemical analysis, thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses. Air-drying after ethanol extraction (EAD) is shown to be more effective than air-drying (AD) in preserving the delaminated structure in the resultant Ti-clay. A broad XRD peak at low 2? angle with a high d-spacing of ca. 6.6 nm was firstly reported and it was proposed to be correlated with the mesoporous delaminated structure rather than the (001) reflection of intercalated/pillared periodic structure. The resulting TiO2-PILC exhibits a good thermal stability as indicated by its surface area after calcination at 600 degrees Celsius. Moreover, calcination above 300 degrees Celsius results in the formation of nanocrystalline anatase in the TiO2-PILC, and the grain size of anatase increases with the increment of calcination temperature. However, no phase transformation from anatase to rutile was observed even under calcination at 1000 degrees Celsius. These fundamental results provide new insights about the structure of TiO2-PILC synthesized by TiCl4 hydrolysis method