V–Ti and V–Al silicate molecular sieves of MFI topology: synthesis and characteristics

Abstract

Doubly substituted V–Ti and V–Al derivatives of silicalite-1 have been synthesized hydrothermally with full yield and crystallinity. The materials have been examined using XRD, SEM, EPM, ICP, SIMS, XRF, DTG/DTA, TPD of ammonia, EPR, static and MAS NMR, UV–VIS, FTIR and Raman spectroscopy. The investigation indicate incorporation of the heteroelements into the framework, give further support for the framework siting of V ions in MFI-type materials and reveal the good thermal and chemical stabilities of the substituted materials. The vanadium ions occur in several different coordinations and can be reversibly oxidized and reduced between V⁴⁺ and V⁵⁺. Introduction of Al or Ti together with V does not influence the state and/or coordination of the V ions.