Reaction mechanism of photooxidation of propane over alkali-metal-ion-modified silica-supported vanadium pentaoxide under irradiation by visible light

Tanaka, Sakae; Tanaka, Tsunehiro; Funabiki, Takuzo; Yoshida, Satohiro

doi:10.1039/a704794k

Cited by 27 publications

(21 citation statements)

References 2 publications

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“…The onset wavelength in the excitation spectrum of CsVS (410 nm) was longer than that of VS (370 nm). This is consistent with results showing that alkali-ion-modified VS excited at 400-nm light emits phosphorescence as reported by Takenaka et al [15,16]. The excitations are assignable to transition from O 2p nonbonding orbitals to π*-like molecular orbitals of V=O and O-V-O moiety for VS and potassium-ion-modified VS (KVS), respectively [17].…”

Section: Resultssupporting

confidence: 80%

Alkali Metal Ion-Modified Vanadium Mononuclear Complex for Photocatalytic Mineralization of Organic Compounds

2010

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Modification of silica-supported vanadium oxide (VS) photocatalysts with alkali metal ions enhanced the photocatalytic activity of the vanadium(V) mononuclear complex for oxidative decomposition of gaseous organic compounds into carbon dioxide. Action spectrum analysis revealed that the onset wavelength for cesium-ion-modified VS was 420 nm, which was ca. 20 nm longer than that with a titania photocatalyst, P25.

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Section: Resultssupporting

confidence: 80%

Alkali Metal Ion-Modified Vanadium Mononuclear Complex for Photocatalytic Mineralization of Organic Compounds

2010

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“…Evidence is based on the observation of transient loss of V-O-H absorption upon photoreaction and the fact that hydroxylated vanadyl centers absorb in the blue spectral region while isolated vanadyl groups in a completely dehydrated state do not. On the other hand, it has been reported that vanadia centers in the hydrated state are not active in photo-oxidation reactions [3,24]. This is confirmed in the present study, since accumulation of water on the catalyst leads to a significantly lower activity in the photo-oxidation of cyclohexene.…”

Section: 2supporting

confidence: 87%

“…Supported vanadium oxides are effective photocatalysts in selective hydrocarbon oxidation, both in gas phase applications [1][2][3] as well as in liquid phase [4].Typically the active vanadia sites are completely dehydrated during reaction and, without promoters, UV radiation is required to photo-activate the catalytic centers [2,3]. Generally water is reported to deteriorate the photocatalytic performance of vanadia catalysts [5] even though hydration shifts the absorption spectrum of these catalysts into the visible [6,7].…”

Section: Introductionmentioning

confidence: 99%

Cyclohexene photo-oxidation over vanadia catalyst analyzed by time resolved ATR-FT-IR spectroscopy

Mul

Wasylenko

Hamdy

et al. 2008

Phys. Chem. Chem. Phys.

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Vanadia was incorporated in the 3-dimensional mesoporous material TUD-1 with a loading of 2% w/w vanadia. The performance in the selective photo-oxidation of liquid cyclohexene was investigated using ATR-FT-IR spectroscopy. Under continuous illumination at 458 nm a significant amount of product, i.e. cyclohexenone, was identified. This demonstrates for the first time that hydroxylated vanadia centers in mesoporous materials can be activated by visible light to induce oxidation reactions. Using the rapid scan method, a strong perturbation of the vanadyl environment could be observed in the selective oxidation process induced by a 458 nm laser pulse of 480 ms duration. This is proposed to be caused by interaction of the catalytic centre with a cyclohexenyl hydroperoxide intermediate. The restoration of the vanadyl environment could be kinetically correlated to the rate of formation of cyclohexenone, and is explained by molecular rearrangement and dissociation of the peroxide to ketone and water. The ketone diffuses away from the active center and ATR infrared probing zone, resulting in a decreasing ketone signal on the tens of seconds time scale after initiation of the photoreaction. This study demonstrates the high potential of time resolved ATR FT-IR spectroscopy for mechanistic studies of liquid phase reactions by monitoring not only intermediates and products, but by correlating the temporal behavior of these species to molecular changes of the vanadyl catalytic site.

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“…We cannot advocate a similar explanation, because, in our case, the (VO x ) n overlayer does not possess the characteristics of phase oxides as in the cited work. As an alternative explanation we advance the possibility that electrons can be released into TiO 2 from the (-V IV -O − ) * excited states [37].…”

Section: Materials Characterization Results Of Ov(or) 3 Uptake By Timentioning

confidence: 93%

Selective Photooxidation and Photoreduction Processes at Surface-Modified by Grafted Vanadyl

Амаделли

Samiolo

Maldotti

et al. 2011

International Journal of Photoenergy

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Titanium dioxide was surface-modified by grafting vanadyl species using vanadyl triisopropoxide as a precursor. The resulting material, (VOx)n/TiO2, was characterized by Raman spectroscopy and photoelectrochemical methods. Photocatalytic oxidation of benzyl alcohol and cyclohexene were used to test oxidation selectivity and 4-nitro-benzaldehyde to assess selective photoreduction. The surface-modified TiO2exhibits an enhanced selectivity to benzaldehyde in the photocatalytic oxidation of benzyl alcohol in an aqueous medium and an increase of cyclohexenol formation in the case of cyclohexene in nonaqueous solvent. The salient result is the 100% selective reduction of the nitrogroup in 4-nitro-benzaldehyde achieved under mild experimental conditions.

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Reaction mechanism of photooxidation of propane over alkali-metal-ion-modified silica-supported vanadium pentaoxide under irradiation by visible light

Cited by 27 publications

References 2 publications

Alkali Metal Ion-Modified Vanadium Mononuclear Complex for Photocatalytic Mineralization of Organic Compounds

Alkali Metal Ion-Modified Vanadium Mononuclear Complex for Photocatalytic Mineralization of Organic Compounds

Cyclohexene photo-oxidation over vanadia catalyst analyzed by time resolved ATR-FT-IR spectroscopy

Selective Photooxidation and Photoreduction Processes at Surface-Modified by Grafted Vanadyl

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