DRIFTS, XPS, XAS, AND AB-INITIO STUDY OF LANTHANIDE OXIDES SUPPORTED ON GAMMA-AL2O3

DRIFTS, XPS, and XAS experiments have been carried out on Ln(2)O(3)/gamma-Al2O3 catalysts. The experimental results have also been modeled by using SCF MO ab initio calculations on clusters simulating the La2O3/gamma-Al2O3 catalysts. A strong interaction between the supported phase and the support is observed that results in the modification of the stretching frequency of Al-O bonds, the binding energy of the lanthanide cations, and the white Line intensity at the lanthanide L(III) XAS spectrum. All these modifications can be explained in light of the ab initio calculations as a result of charge redistribution between aluminium and lanthanide cations through an oxygen bridge. This charge redistribution is a function of the number and nature of the cations of the second coordination sphere of the lanthanide element, which justify the differences in chemical reactivity of the catalysts as a function of the loading and calcination temperature.