CO- and N2-FTIR Characterisation of Oxidised Rhodium Species Supported on Ce0.68Zr0.32O2
Résumé
The identification of Rh oxidised species of a Rh(0.29)/Ce0.68Zr0.32O2 catalyst, exhibiting peculiar CO-O2 kinetics [Manuel et al., J. Catal. 2004, 224, 269], is addressed. For this purpose, various catalysts are studied by XANES, CO- and N2-FTIR, and benzene hydrogenation. The results obtained, and more particularly N2-FTIR, which is, to our knowledge, reported for the first time on this kind of catalyst, suggest that Rh is mainly stabilised as electron-deficient clusters (Rhn Δ+) on a Rh(0.29)/Ce0.68Zr0.32O2 catalyst after reduction at 500 °C under H2. The existence of these species, which would be due to electron perturbation induced on the metal by the reduced support or electron withdrawal from the metal clusters by inductive effect of the neighbouring Cl anions, is also revealed through CO-FTIR experiments. In the presence of CO, however, evidence of RhI(CO)2 species is provided as well.