, Volume 21, Issue 3-4, pp 303-308

Effects of adsorbed oxygen containing molecules on the XANES of Pt in supported Pt/SiO2 catalysts

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Abstract

The variation of the X-ray absorption coefficient above the Pt-LIII edge after adsorption of crotonaldehyde, butyraldehyde, crotylalcohol and butanol on a Pt/SiO2 catalyst was studied by means of X-ray absorption spectroscopy. The adsorption of these molecules caused the intensity of the white line to decrease in the order CrHO>CrOH∼BuHO≫>BuOH. From this we concluded that adsorbed unsaturated compounds donate electrons from their double bonds to Pt. The magnitude of the observed effects was approximately equal for the C=O and the C=C group. Over the Pt/SiC2 catalysts studied, crotonaldehyde was concluded to be adsorbed via both double bonds. The interaction of the free electron pairs of the oxygen was concluded to be significantly weaker than the interaction of the electrons in the π-bonds.