129Xe NMR study of 12-tungstophosphoric heteropoly acid supported on silica

The structure of 12-tungstophosphoric heteropoly acid (H₃PW₁₂O₄₀) supported on silica has been studied by¹²⁹Xe NMR of adsorbed xenon. The¹²⁹Xe NMR spectra are found to depend on the surface HPA concentration. The¹²⁹Xe NMR data provide evidence for the presence of an organized microporous structure within HPA overlayers. These results are in agreement with nitrogen adsorption and capillary condensation (77 K) measurements. The high sensitivity of the¹²⁹Xe NMR method and its applicability for testing of silica-based HPA catalysts are demonstrated.A preliminary report of this work was presented to the Second European Congress on Catalysis EUROPACAT-II, Maastricht, The Netherlands, 3–8 September 1995.Deceased.