1H, 51V and 15N nuclear magnetic resonance studies of structure and properties of vanadia supported on [formula omitted

Abstract

1H magic-angle spinning nuclear magnetic resonance (MAS NMR) spectra of TiO x SiO 2 catalysts suggest the interaction of surface TiO x . species with Si-OH groups of the silica. Simultaneously, Ti-OH groups from surface titania species appear. The distribution of TiO x species over SiO 2 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 SiO 2 surface. Deposition of titania as well as vanadia produces strong electron-accepting (Lewis) sites which interact with the terminal N atom of adsorbed N 2O 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.