| Popis: |
The La2O3/Al2O3 composite oxides were characterized in terms of their point of zero charge (pzc) and surface area. A model, describing lanthana dispersed as hemispherical clusters, was used to analyze the results. The model parameters calculated from experimental results are in general agreement with those obtained by X-ray diffraction results. The model was used to estimate the surface area of the individual components, lanthana and alumina, in the composite oxide. As the lanthana weight loading increases, the surface area of the lanthana dispersed in a La2O3/Al2O3 composite oxide increases and reaches a plateau at 8% La2O3 loading. The total BET surface area of the composite oxide decreases sharply as the lanthana loading increases above 8%. The surface area considerations suggest that the optimum lanthana loading (maximum in supported lanthana surface area per gram of composite oxide used) in a composite oxide is ∼ 8%. |
