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Multilayered SiO 2 /TiO 2 Nanosol Particles in Two-Dimensional Aluminosilicate Catalyst−Support

1998; American Chemical Society; Volume: 102; Issue: 31 Linguagem: Inglês

10.1021/jp9815863

1520-6106

Jin‐Ho Choy, Joo-Hyoung Park, Joo‐Byoung Yoon,

Layered Double Hydroxides Synthesis and Applications

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 °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 °C were found to increase from 35.4 Å, to 47.3 Å, and to 60.0 Å as the ion exchange reaction temperature was raised from 40 °C, to 60 °C, and to 75 °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 m2/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 129Xe 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.