Studies on catalytically active surface compounds. 7

The catalytic properties of silica supported vanadium-chromium catalysts for the oxidation of ethanol, butane, propene, and butene are described and completed by ESR measurements. Differences in catalytic activity of chromium-free vanadium catalysts which are caused by different values of the silanol group concentration of the support are shown to become levelled by the addition of chromium. V-O-Cr species of medium catalytic activity are considered to be the catalytic active center. ESR spectra taken after the reaction show the existence of Cr3+ and VO+2 species. A correlation between the intensity of the VO2+ signal and the catalytic activity of the samples is observed. (author)