Xe NMR Study of Ti 02 ( Anatase )-Supported v 2 0 5 Catalysts

Ti02 (anatase), V2O5, and V2OdTi02 (anatase) catalysts with 1.3%, 3.0%, and 9.8% weight loadings of V2O5 have been studied using temperature-dependent xenon129 NMR spectroscopy. The intrinsic chemical shift values due to the interaction of xenon with the surface are 109 f 3 ppm for Ti02 (anatase) and 93 f 5 ppm for V2O5. The V2O5/TiO2 catalysts provide strong adsorption sites for xenon which cause an initial decrease of the chemical shift values at low xenon loadings. Additionally, the spectra of pure V2O5 reveal two distinct environments for the xenon atoms, consistent with the hysteresis of the isotherm and the existence of pores. Two-dimensional exchange spectroscopy was used to measure the rates and activation energy of xenon moving between these two environments.