EPR studies of the coverage effects in TiO[sub 2](B)-supported vanadia catalysts for toluene ammoxidation

Journal Article · Sun Nov 01 00:00:00 EST 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90008-6· OSTI ID:5650295

Jansen, S; Tu, Y; Palmieri, M J ^[1]; Sanati, M; Andersson, A ^[2]

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1. Temple Univ., Philadelphia, PA (United States)
2. Univ. of Lund (Sweden)

EPR spectroscopy has been employed to determine the nature of vanadium (+4) species in the TiO[sub 2](B)-supported vanadia catalysts. IR and EPR studies show that multiple vanadia species are observed as a function of loading. At coverages greater than 3.5 theoretical layers, the EPR signal is reminiscent of bulk V[sub 2]O[sub 5]. At lower coverages, a different magnetic species dominates the resonance and may be attributable to tetrahedral states of vanadium at the oxide interference. The spin concentration and [g] suggest two distinct vanadia phases as a function of coverage. In this study, we have also analyzed catalysts after use in ammoxidation of toluene. These samples show strikingly different features compared with the freshly prepared samples. Changes in both the g-anisotropy and hyperfine coupling were observed relative to the fresh catalysts. Though EPR is not surface sensitive, inference into the nature of the catalytic surface can be made by comparison of catalysts of different coverage and studies of monolayer samples. A study of the TiO[sub 2](B)-vanadia interface was made by comparing monolayer catalysts prepared from slightly different techniques. Our measurements show strikingly different features in V[sup 4[minus]] species as a function of preparation. 45 refs., 6 figs., 2 tabs.

• OSTI ID: 5650295
• Journal Information: Journal of Catalysis; (United States), Vol. 138:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
TITANIUM OXIDES
CATALYTIC EFFECTS
TOLUENE
OXIDATION
VANADIUM OXIDES
ANISOTROPY
CATALYST SUPPORTS
CATALYSTS
ELECTRON SPIN RESONANCE
HETEROGENEOUS CATALYSIS
LAYERS
ALKYLATED AROMATICS
AROMATICS
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
HYDROCARBONS
MAGNETIC RESONANCE
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RESONANCE
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties