TiO2/SiO2 mixed oxide catalysts prepared by sol—gel techniques. Characterization by solid state CP/MAS spectroscopy

29Si CPMAS NMR and near-IR study of sol–gel microporous silica with tunable surface area

“…The efficiency of the magnetization transfer from the 1 H nuclei to silicon nuclei is governed by the characteristic proton spin-lattice relaxation time in the rotating frame (T 1q ) and the silicon-proton cross-polarization time (T SiH ). Considering that the 29 Si-1 H cross-polarization is more efficient in magnetization transfer for those silicon nuclei with directly bound hydroxyl groups [25][26][27][28][29], this method provides information about the surface of the silica. Thus, Q 4 contribution in the CPMAS spectra are considerable lower respect to MAS spectra, since only Q 4 groups close to the surface are detected.…”

“…Signal to noise ratio for the low abundant 29 Si nucleus can be improved through the combination of MAS with cross polarization technique [25][26][27][28]. The efficiency of the magnetization transfer from the 1 H nuclei to silicon nuclei is governed by the characteristic proton spin-lattice relaxation time in the rotating frame (T 1q ) and the silicon-proton cross-polarization time (T SiH ).…”

Solid State NMR Interaction Parameters of Oxygens Linking Titanium and Silicon in Crystalline Cyclic Titanodiphenylsiloxanes

“…Oxygen bridges of the type Si-O-Ti are central to these properties but, until now, there is little knowledge concerning the existence, and in particular the amount, of these heterometal bonds in such amorphous solids. Techniques like IR or Raman spectroscopies [4], X-ray absorption [5], and 29 Si NMR [6,7] can be used to characterize the presence of Si-O-Ti bonds. There has been considerable interest in using 29 Si NMR to investigate the effect of titanium in a wide range of TiO 2 -SiO 2 materials.…”

Inhomogeneities in acid-catalyzed titania–silica and zirconia–silica xerogels as revealed by small-angle x-ray scattering

“…A sol of water and metal alkoxide(s) undergoes hydrolysis and condensation reactions to produce a gel. They have previously been investigated using diffraction, [6][7][8][9] ultraviolet, 10 infrared, [10][11][12][13] nuclear magnetic resonance (NMR), 11,12,14 and x-ray absorption spectroscopies. This becomes similar to a melt-quenced glass during heat treatment (up to ∼1000°C).…”