TDPAC CHARACTERIZATION OF MO SPECIES SUPPORTED ON ALUMINA MODIFIED BYTITANIA

The TDPAC (time differential perturbed angular correlation) technique, already applied to the study of molybdenum oxide species supported on alumina, is used to investigate the same oxide on the novel support T iO2/Al2O3. Mo-99 obtained by neutron irradiation of natural molybdenum in the samples is used as a TDPAC probe. Measurements in the range fr om room temperature to 280 degrees C are pet-formed on samples with 16 and 8 wt% MoO3 to find out the dispersion of adsorbed species. The ab ove-mentioned dispersion is the main characteristic that has influence on the catalytic properties in the heterogeneous catalyst. The corres ponding results allow us to determine the hyperfine parameters and con centrations of both MoO3 and two-dimensional Mo oxides on this support . Two of the three different Mo environments in the samples can be att ributed to the presence of monolayer species. This is compatible with the presence of Mo-O crystallites with a surface of approximately 10 n m(2).