Mastikhin VM, Terskikh VV, Lapina OB, Filimonova SV, Seidl M, Knözinger H. 1H, 51V and 15N nuclear magnetic resonance studies of structure and properties of vanadia supported on TiO chi/SiO2.
SOLID STATE NUCLEAR MAGNETIC RESONANCE 1995;
4:369-379. [PMID:
8581435 DOI:
10.1016/0926-2040(95)00020-q]
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Abstract
1H magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of TiO chi/SiO2 catalysts suggest the interaction of surface TiO chi species with Si-OH groups of the silica. Simultaneously, Ti-OH groups from surface titania species appear. The distribution of TiO chi species over SiO2 is non-uniform, since a considerable part of surface OH groups remains unreacted with supported titania. Supported vanadia species interact both with Si-OH and Ti-OH groups. 51V NMR spectra suggest the interaction of vanadia with supported titania species and show the non-uniform distribution of titania over the SiO2 surface. Deposition of titania as well as vanadia produces strong electron-accepting (Lewis) sites which interact with the terminal N atom of adsorbed N2O molecules, resulting in a downfield shift of the resonance in 15N NMR spectra. The acid strength of electron-accepting sites is similar in both cases. Only about 10% of the total amount of supported titania and vanadia create Lewis sites.
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