Surface chemical structures of V//2O//5-P//2O//5 catalysts were investigated by using X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), temperature-programmed desorption (TPD) of NH//3, infrared spectra of adsorbed NH//3 and pyridine, and the NARP (nitric oxide-ammonia rectangular pulse) technique. The concentration of the surface V equals O species remarkably increased with P//2O//5 content below P/V equals 1. 0, but it decreased on further addition of P//2O//5. The increase in the surface V equals O species was attributed to the lower oxidation state of vanadium ions in the bulk of the V//2O//5-P//2O//5 catalysts. The addition of P//2O//5 increased the surface concentration and the strength of acid sites, which consist mostly of Bronsted acid sites and of a slight amount of Lewis acid sites.
|Number of pages||8|
|Journal||Journal of physical chemistry|
|Publication status||Published - 1988 Jan 1|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry