The effect of the framework structure on the chemical properties of the vanadium oxide species incorporated within zeolites

• Published in: Catalysis today Vol. 78; no. 1; pp. 211 - 217
• Main Authors: Anpo, Masakazu, Higashimoto, Shinya, Matsuoka, Masaya, Zhanpeisov, Nurbosyn, Shioya, Yasushi, Dzwigaj, Stanislaw, Che, Michel
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 28.02.2003; Elsevier Science
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; ESR; Exact sciences and technology; General and physical chemistry; Ion-exchange; Photoluminescence; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Vanadium silicalites; XAFS; Zeolites: preparations and properties; Vanadium silicalites; ESR; XAFS; Photoluminescence; Transition metal Compounds; EPR spectrometry; Vanadium; Zeolite; Experimental study; Supported catalyst; EXAFS spectrometry; Molecular sieve; Heterogeneous catalysis; Local structure; Preparation; Silicon Oxides; Vanadium oxide; Hydrothermal condition; Modified material; Crystalline structure
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/S0920-5861(02)00339-5

V-silicalite catalysts (VS-1 and VS-2) prepared by hydrothermal synthesis have been studied by ESR, XAFS (XANES and EXAFS) and photoluminescence spectroscopy. The in situ characterization of these V-silicalites shows that vanadium is present within the zeolitic framework as a highly dispersed tetrahedrally coordinated V-oxides, VO 4 unit, having a short VO bond length. Photoluminescence spectroscopy in static and dynamic mode, as well as XAFS studies allow to detect in the V-silicalites different V species than that present in V-HMS or V/SiO 2, in terms of VO bond length, vibrational energy, ▪ bond angle and lifetime of the excited triplet state. It is suggested that the combined contribution of the neighboring SiOH group attached to the VO 4 unit and the zeolitic rigid framework structure of V-silicalites cause a more significant and pronounced effect on the chemical properties of the VO 4 unit than the flexible structure of V-HMS or V/SiO 2. Moreover, the dynamic quenching of the phosphorescence by the addition of reactant molecules such as NO or propane indicates that the V species in the excited triplet state can be expected to be the active sites for the photocatalytic reactions.