Multilayered SiO2/TiO2 nanosol particles in two-dimensional aluminosilicate catalyst-support

A new layered nanocomposite, which is one-to-one interstratified with a montmorillonite layer and a mixed SiO2/TiO2 sol particle one, has been prepared by ion exchange reaction of the Na+ ion in montmorillonite with the positively charged SiO2/TiO2 sol particles. The ion exchange reaction was performed at three different temperatures of 45, 60, and 75 degrees C by mixing an aqueous suspension of 1 wt % Na+ montmorillonite with SiO2/TiO2 sol solution where the molar ratio of Si/Ti was selected as 20/2. According to the powder X-ray diffraction analysis, the basal spacings of layered nanocomposites calcined at 400 degrees C were found to increase from 35.4 Angstrom, to 47.3 Angstrom, and to 60.0 Angstrom as the ion exchange reaction temperature was raised from 40 degrees C, to 60 degrees C, and to 75 degrees C. Their BET and Langmuir specific surface areas and porosities, estimated from nitrogen adsorption-desorption isotherms, become larger with the increment of basal spacing, and the highest BET specific surface area and the largest porosity are found to be 683 m(2)/g and 0.50 mL/g, respectively. Despite the large increment of the basal spacing, the porous properties such as specific surface areas, porosities, and pore sizes, those which are calculated from t-plots and chemical shift of Xe-129 NMR, respectively, are determined to be almost constant. From the UV/vis spectra, the blue shift of the absorption edge was observed, indicating that the TiO2 sol particles in the interlayer are quantum sized. It is therefore proposed that the products are intercalation-type nanocomposites with the multistacked structure of the SiO2/TiO2 nanoparticles in the interlayer space of montmorillonite.