High Dispersion Metal Oxide/Molecular Sieves: New Bifunctional Shape Selective Catalysts

Highly dispersed metal oxide/molecular sieve catalysts can be prepared through modification of metallosilicate molecular sieves. The resulting materials have been shown to exhibit enhanced catalytic activities for selected reactions. The metallosilicates examined include the gallosilicates, iron (ferri-) silicates and cobalt silicates. The size of the metal oxide particles as well as their location (in the pores or on the surface) can be controlled through post-synthesis methods. Thermal or mild hydrothermal treatment of the metallosilicate produces a highly dispersed metal oxide phase, while higher temperatures or longer treatment causes the metal oxide to migrate and form larger agglomerates of the metal oxide phase. The size of these agglomerates are strongly dependent on the conditions of hydrothermal treatment. Dispersion, location and agglomeration of the metal oxide phase have been characterized for the iron silicates using both physical and catalytic techniques. The magnetic properties of the iron silicates are described.