HYDROGENATION OF CARBON-MONOXIDE - EVIDENCE OF A STRONG METAL SUPPORT INTERACTION IN RH/ZRO2 CATALYSTS

Temperature-programmed desorption (TPD) studies are reported on a series of Rh catalysts dispersed on ZrO2 and γ-Al2O3 and activated under H2 flow at 250, 400, and 600°C. While the high temperature of activation did not show any significant difference in the Rh γ-Al2O3 samples, in the case or Rh ZrO2 a pronounced effect is quite evident. The experimental observations have been associated to a modification of the metal-support interface, for which a possible model is suggested. Parallel experiments in the hydrogenation of carbon monoxide at 220°C and P = 1 atm have shown a sharp decrease in the overall activity while the selectivity was virtually unaffected by the temperature of reduction.