DETERMINATION OF THE ACCESSIBLE METALLIC SURFACE OF SUPPORTED PLATINUM - QUANTITATIVE INFRARED SPECTROSCOPIC STUDY OF CARBON-MONOXIDE ADSORPTION

Catalysts containing platinum on carriers which do not exhibit strong metal support interaction (SMSI) behaviour have been prepared. Metal dispersion was measured by volumetric chemisorption measurements. Adsorption of carbon monoxide on the same samples was followed by infrared spectroscopy. A linear relationship was found between the optical density of the band due to carbon monoxide linearly bonded to platinum and the metallic area accessible to gases measured either by hydrogen and oxygen chemisorptions or by hydrogen-oxygen titration. Platinum supported on carriers liable to exhibit a SMSI character has also been examined. When direct chemisorption of hydrogen is higher than the experimental error, the value of the metallic area so obtained is in good agreement with the corresponding infrared determination. Hydrogen-oxygen titration measurements are not suited to the determination of the metallic surface for catalysts exhibiting a SMSI behaviour. The spectroscopic method seems to be suitable for the measurement of the metallic surface area of automotive post combustion catalysts. © 1990.