V-TI AND V-AL SILICATE MOLECULAR-SIEVES OF MFI TOPOLOGY - SYNTHESIS AND CHARACTERISTICS

Doubly substituted V-Ti and V-Al derivatives of silicalite-1 have been synthesized hydrothermally with full yield and crystallinity. The mat erials 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 spec troscopy. The investigations indicate incorporation of the heteroeleme nts into the framework, give further support for the framework siting of V ions in MFI-type materials and reveal the good thermal and chemic al stabilities of the substituted materials. The vanadium ions occur i n several different coordinations and can be reversibly oxidized and r educed between V4+ and V5+. Introduction of Al or Ti together with V d oes not influence the state and/or coordination of the V ions.