XE-129 NMR-STUDY OF 12-TUNGSTOPHOSPHORIC HETEROPOLY ACID SUPPORTED ONSILICA

The structure of 12-tungstophosphoric heteropoly acid (H3PW12O40) supp orted on silica has been studied by Xe-129 NMR of adsorbed xenon. The Xe-129 NMR spectra are found to depend on the surface HPA concentratio n. The Xe-129 NMR data provide evidence for the presence of an organiz ed microporous structure within HPA overlayers. These results are in a greement with nitrogen adsorption and capillary condensation (77 K) me asurements. The high sensitivity of the Xe-129 NMR method and its appl icability for testing of silica-based HPA catalysts are demonstrated.