2010
DOI: 10.1021/jp103269w
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Molecular Structural Determination of Molybdena in Different Environments: Aqueous Solutions, Bulk Mixed Oxides, and Supported MoO3 Catalysts

Abstract: UV-vis diffuse reflectance spectroscopy (DRS) and Raman spectroscopy were used to examine the electronic and molecular structures, respectively, of well-defined Mo(VI) bulk mixed oxide reference compounds ((i) isolated MoO 4 or MoO 6 monomers, (ii) dimeric O 3 Mo-O-MoO 3 , (iii) chains of alternating MoO 4 and MoO 6 units, (iv) MoO 6 -coordinated Mo 7 -Mo 12 clusters, and (v) infinite layered sheets of MoO 5 units), aqueous molybdate anions as a function of solution pH, and supported MoO 3 catalysts (MoO 3 /Si… Show more

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Cited by 170 publications
(221 citation statements)
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“…[36] We can thus confirmt he presence of Keggin-type heteropolyanion structurea fter 300 8Ca nd 400 8Ct reatment in scCO 2, previously observed by X-ray diffraction ( Figure 1). The three spectra are quite similar,a lthough one can suspectf rom minor structure distortion in sample scMoP(400 8C, 1h)b yc omparing n Mo-Od bands intensities ratio (bands centereda t9 87 cm À1 and 962 cm…”
supporting
confidence: 83%
See 1 more Smart Citation
“…[36] We can thus confirmt he presence of Keggin-type heteropolyanion structurea fter 300 8Ca nd 400 8Ct reatment in scCO 2, previously observed by X-ray diffraction ( Figure 1). The three spectra are quite similar,a lthough one can suspectf rom minor structure distortion in sample scMoP(400 8C, 1h)b yc omparing n Mo-Od bands intensities ratio (bands centereda t9 87 cm À1 and 962 cm…”
supporting
confidence: 83%
“…One can observe sharp bandsa t9 84-986cm À1 and 961-967 cm À1 assigned to n Mo-Od symmetric and n Mo-Od asymmetric MoO 6 stretch, respectively, [35,36] Bands centered at around 600 cm À1 (interval 500-700 cm…”
Section: Introductionmentioning
confidence: 99%
“…It was reported by Wachs and co-workers [33,34] that this band is attributed to the presence of di-oxo chromate species (Si O) 2 Cr( O) 2 . Moreover, a very small shoulder was also observed at 1012 cm −1 (clearly visible in Cr-2.5 spectrum), this shoulder was described to be attributed to the presence of monoxo chromate species (Si O) 3 Cr( O).…”
Section: Samplementioning
confidence: 77%
“…Moreover, a very small shoulder was also observed at 1012 cm −1 (clearly visible in Cr-2.5 spectrum), this shoulder was described to be attributed to the presence of monoxo chromate species (Si O) 3 Cr( O). The bands between 325 and 400 cm −1 are attributed to the O Cr O bending modes [33,34]. Fig.…”
Section: Samplementioning
confidence: 95%
“…[248][249]506] Under fully oxidized conditions,d i-oxo (SiO) 2 W(=O) 2 and mono-oxo (SiO) 4 W(=O) sites are observed, in addition to WO 3 nanoparticles/clusters.T he relative amounts of these species depend on the Wl oading. [510][511][512][513] At coverages above one monolayer (4.6 Mo nm À2 ), crystalline MoO 3 nanoparticles are also found. [446] The molecular structures of fully oxidized Mo catalysts on different supports (SiO 2 ,A l 2 O 3 ,a nd SiO 2 -Al 2 O 3 )w ere also extensively studied by in situ Raman, IR, and UV/Vis spectroscopy as well as DRS and XAS.T hese methods [507] as well as DFT calculations [508,509] indicate that surface di-oxo 4 Mo-( = O) sites are formed at higher coverage.…”
Section: Surface Sites In Industrial Catalystsmentioning
confidence: 98%