Studies on crystalline microporous vandium silicates

Journal Article · Tue Jun 01 04:00:00 EDT 1993 · Journal of Catalysis; (United States)

OSTI ID:6154118

Hari Prasad Rao, P R; Belhekar, A A; Hegde, S G; Ramaswamy, A V; Ratnasamy, P ^[1]

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1. National Chemical Laboratory, Pune (India)

Three crystalline, microporous, vanadium silicates, VS-2 (Si/V = 79,122, and 161, respectively) with MEL structure have been synthesized. The spectroscopic (IR, NMR, and ESR) features and catalytic properties (in the oxidation of toluene and xylenes by H[sub 2]O[sub 2]) have been elucidated. IR spectra of the adsorbed ammonia and pyridine reveal the presence of both weak Bronsted and Lewis acid sites. There is a direct correlation between the concentration of hydrogen-bonded hydroxyl groups and the amount of vanadium incorporated in the material. In carefully prepared samples of VS-2, the [sup 51]V MAS-NMR studies reveal the presence of only a single vanadium species with a chemical shift parameter (-573 ppm) and a signal linewidth (50 ppm) similar to those observed in monomeric orthovanadates having tetrahedrally coordinated vanadium ions. Clusters of vanadium as well as V[sub 2]O[sub 5]-like phases are absent. A linear increase in the intensity of the ESR peaks with both the vanadium content and unit cell volume of the MEL phase suggests that the V[sup 4+] ions are associated, in a manner yet undefined, with the MEL lattice. VS-2 oxidizes toluene to a mixture of cresols, benzyls alcohol, and benzaldehyde. The differences in the rates of oxidation of xylene isomers confirms that most of the V ions are located inside the channel system of MEL. 23 refs., 6 figs., 2 tabs.

• OSTI ID: 6154118
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 141:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ALKYLATED AROMATICS
AROMATICS
BROENSTED ACIDS
CATALYSIS
CATALYTIC EFFECTS
CHARGED PARTICLES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMICAL SHIFT
ELECTRON SPIN RESONANCE
HETEROGENEOUS CATALYSIS
HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INTERMEDIATE MASS NUCLEI
IONS
ISOMERS
ISOTOPES
KINETICS
LEWIS ACIDS
MAGNETIC RESONANCE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
OXIDATION
OXYGEN COMPOUNDS
POROSITY
REACTION KINETICS
RESONANCE
SILICATES
SILICON COMPOUNDS
SPECTROSCOPY
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
TOLUENE
TRANSITION ELEMENT COMPOUNDS
VANADIUM 51
VANADIUM COMPOUNDS
VANADIUM IONS
VANADIUM ISOTOPES
VANADIUM SILICATES
XYLENES