Where is the metal in metallosilicate molecular sieves ? An examination of some vanadosilicates

Abstract

Metallosilicate molecular sieves result when the Al³⁺ ions in zeolitic materials (aluminosilicate) are replaced (isomorphous substitution) by other ions. A large number of metal ions have reportedly been incorporated in zeolite lattices. However, doubts arise regarding the location of these metal ions in the framework in many cases. Detailed characterization of the metallosilicates is necessary to identity the nature and location of the metal ions. As an example, the types of V-ions present in vanadosilicate molecular sieves of MEL, MFI and BEA structure types are discussed based on detailed physicochemical characterization of these materials. Also, the influence of preparation methods on the type and location of the V-ions are reported.