Infrared study of water and pyridine adsorption on the surface of anhydrous vanadyl pyrophosphate

Abstract

Infrared spectra of vanadyl pyrophosphate contained a broad maximum at 2550–3550 cm^–1 which exchange experiments with deuterium oxide showed could be primarily attributed to residual OH-containing species in the bulk crystal lattice. However, the presence of Brønsted-acidic surface hydroxy groups was exhibited by the generation of adsorbed pyridinium ions when (VO)₂P₂O₇ was exposed to pyridine vapour. Pyridine was also adsorbed on Lewis-acidic surface sites, some of which were converted to Brønsted-acidic sites by the adsorption of water.