Faujasite transition metal forms

The number of reactions catalyzed by zeolites is continually increasing. Synthetic faujasites containing transition metal cations are active for the complete oxidation of H2, CO, C2H4, NH3 (9). Upon interaction of NH3 with 02 over CrY and AgY, N20 and N2 are formed (9). Mahida et al. (21) investigated the oxidation of propylene over Cu2+Y. Depending on the temperature and on the water vapor content in the reaction mixture,... 

Upon exposure of transition metal (Mn11, Fem, Cu11, Co11) exchanged zeolites to dicyanobenzene (DCB), encapsulated MePc complexes are formed in the faujasite supercages, according to the following stoichiometry ... 

The ship-in-a-bottle technique is perhaps the most common method for encapsulation of transition metal complexes. In this way the tetradentate Schiff base ligand SALEN (bis-salicylidene) ethylenediamine can diffuse through the 12 MR windows of faujasite. Then, when complexed with a previously exchanged metal ion, nearly square planar coordination geometry is formed inside the a-cages [97-100], Mn complexes with a chiral ligand, prepared by the ship-in-a-bottle technique inside Y and EMT zeolites, have enantioselectively carried at the epoxidation of olefins [101,102]. 

Gentle treatment under a CO atmosphere is sufficient to convert some transition metal ions in zeolites into zeolite entrapped metal carbonyl clusters. Such clusters are usually formed under milder conditions in faujasite cages than in solution. This comparison illustrates the excellent solvating abilities of the cages. 

Zeolite catalysts have also been proposed for stationary SCR applications, mainly in gas-fired cogeneration plants. Zeolites in the acid form, in which transition metal ions (eg, Fe, Co, Cu, Ni) are introduced in the structure to improve the SCR activity, guarantee high de-NOx activity even at high temperatures to a maximum of 600° C, where metal oxide based catalysts are thermally unstable. The use of metal-exchanged zeolite-based catalysts with distinct structures has been proposed, for example, mordenite, faujasite (both of X and Y types), and ZSM-5 (21,22). Techniques to remove the aluminum oxide from the crystal matrix can be conveniently applied to increase the Si/Al ratio and accordingly the thermal stability of the zeolite and at the same time to limit its tendency to sulfatation. 

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