Abstract
The influence of water on the dispersion and structure of silica SBA-15-supported vanadia model catalysts has been studied using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, which were combined within one experimental setup, as well as UV−vis diffuse reflectance spectroscopy. By performing time-dependent XPS experiments, the influence of UHV/X-ray radiation could be eliminated by extrapolation of the observed temporal changes to t = 0. XPS characterization reveals that the V2p3/2 emission consists of two contributions, which are assigned to vanadia with distinctly different cluster size. Dehydration by treatment in oxygen flow at elevated temperatures leads to a significant increase in total intensity and a substantial redistribution of spectral weight to higher binding energies as a result of an increase in the vanadia dispersion. The V/Si XPS intensity ratio of the dehydrated samples closely follows the corresponding bulk ratio over the whole range of vanadium loadings (0−22 wt % V) st...
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