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

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 2θ angle with a high d-spacing of ≈6.6 nm was firstly reported and it was proposed to be correlated with the mesoporous delaminated structure rather than the (0 0 1) 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 °C. Moreover, calcination above 300 °C 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 °C. These fundamental results provide new insights about the structure of TiO2-PILC synthesized by TiCl4 hydrolysis method.