Characterization of Vanadium and Titanium Oxide Supported SBA-15

Segura, Yolanda; Cool, Pegie; Kuśtrowski, Piotr; Chmielarz, Lucjan; Dziembaj, R.; Vansant, E. F.

doi:10.1021/jp0507750

Cited by 55 publications

(42 citation statements)

References 27 publications

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“…Furthermore, the broadness of the 915 cm À1 Raman band was attributed to thermal movement of the bound oxygen molecule. Most papers in the literature, however, suggest a Raman band in this area to be a V-O-support vibration [55,56,67,81,82,[85][86][87][88][89]. Our data of the dehydrated catalysts show that the Raman band at 915 cm À1 is present at all vanadium oxide loadings, and since the EXAFS results exclude di-or polymeric species, this eliminates the spectral assignment to a V-O-V vibration.…”

mentioning

confidence: 48%

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

Keller

Visser

Soulimani

et al. 2007

Vibrational Spectroscopy

125

130

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The effect of hydration on the molecular structure of silica-supported vanadium oxide catalysts with loadings of 1-16 wt.% V has been systematically investigated by infrared, Raman, UV-vis and EXAFS spectroscopy. IR and Raman spectra recorded during hydration revealed the formation of V-OH groups, characterized by a band at 3660 cm À1. Hydroxylation was found to start instantaneously upon exposure to traces of water, reflecting a very high sensitivity of the supported vanadium oxide catalysts for H 2 O. Further hydration resulted in the appearance of a V-O-V vibration band located around 700 cm À1 pointing to the formation of di-or polymeric species. EXAFS analysis at 77 K indicated structural changes as the oxygen coordination changed from four to five. Moreover, a VÁ Á ÁV contribution was detected for the hydrated species. The IR, Raman and UV-vis data suggested a pyramidal anchoring of the dehydrated VO x species, whereas, the EXAFS data pointed to the presence of single V-O-Si bonded VO x species. This difference is attributed to water condensation effects at 77 K during EXAFS acquisition, resulting in a partial re-hydroxylation of the dehydrated samples, as confirmed by complementary IR and Raman analysis. as well as literature led to a reaction scheme in which a monomeric VO x species anchored by three Si-O-V bonds to the silica support (pyramidal-type structure) is transformed into a monomeric VO x species anchored by one Si-O-V bond (umbrella-type structure) by partial hydration of the catalyst material. This results in the formation of both V-O-H and Si-O-H bonds. At higher water pressures, larger vanadium oxide clusters are formed due to full hydration of the catalyst surface and a de-attachment of the vanadium oxide from the support surface. The results of this study provide evidence, that an umbrella-type structure (i.e., Si-O-V O(OH) 2 ) could be present under catalytic conditions where H 2 O is a reaction product (e.g., partial oxidation of methanol to formaldehyde and oxidative dehydrogenation of alkanes). In other words, both the pyramidal ((Si-O) 3 -V O) and the umbrella (Si-O-V O(OH) 2 ) model can exist at a support surface, their relative ratio depending on the hydration degree of the catalyst material. This study also illustrates that a corroborative characterization requires the use of multiple spectroscopic techniques applied at the same samples under almost identical measuring conditions. #

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mentioning

confidence: 48%

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

Keller

Visser

Soulimani

et al. 2007

Vibrational Spectroscopy

125

130

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“…The pore-size distribution was determined from the desorption branch of the isotherm using the BJH method. Transmission electron microscopy (TEM) was performed using a Philips CM 200 LaB 6 at an acceleration voltage of 200 kV.…”

Section: Physical Characterizationmentioning

confidence: 99%

“…Furthermore, it opens the possibility to study catalysis on well-defined, spatially separated transition metal centers. Despite its great potential use for catalytic applications, there have been only few reports on the preparation and application of SBA-15 supported vanadium oxide catalysts [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Employing spectroscopic techniques such as infrared, UV-Vis, Raman, NMR, and EXAFS, the formation of the adsorbed precursor and the final catalyst were characterized [32]. By using molecular designed dispersion (MDD) of VO(acac) 2 , highly dispersed VO x species have been grafted onto SBA-15 [6]. In this study, the structure of the adsorbed VO(acac) 2 precursor and the final catalyst have been studied using FTIR, Raman spectroscopy and thermogravimetric analysis (TGA), respectively.…”

Section: Introductionmentioning

confidence: 99%

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The mechanism for the controlled synthesis of highly dispersed vanadia supported on silica SBA-15

Heß

Wild

Schlögl

2006

Microporous and Mesoporous Materials

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The mechanism for the controlled synthesis of highly dispersed vanadia supported on mesoporous silica SBA-15 (VO x /SBA-15) is elucidated using X-ray photoelectron spectroscopy (XPS), Raman and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). The synthesis consists of functionalization of SBA-15 using 3-aminopropyltrimethoxysilane (APTMS) followed by HCl treatment, anion exchange of decavanadate (V 10 O 28 6-) and calcination to yield the final material. Spectroscopic analysis yields that APTMS is grafted onto the surface via hydroxyl groups. Under ambient conditions, protonated APTMS on SBA-15 is largely hydrolyzed and present in its bidentate and tridentate form. Detailed XPS analysis reveals a strong influence of surface water on the resulting structure of APTMS on SBA-15. Under dry conditions, the protonated APTMS molecules on SBA-15 adopt the monodentate and bidentate form. During the anion exchange reaction, decavanadate is incorporated intactly into the pores, without any changes in the structure of the organic framework. In the calcination step, decavanadate is decomposed and vanadia is anchored onto the surface of SBA-15 via silanol groups resulting in highly dispersed surface vanadia species, while the organic resiues are fully removed from the pores of the silica matrix. d

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“…Recently, direct synthesis of Ti-substituted SBA-15 with structural integrity under hydrothermal conditions in the absence of acid has also been studied using titanium tetrachloride and tetraethyl orthosilicate as the titanium and silica sources, respectively [9]. In addition, several strategies for the post-synthesis have been used to prepare Ti-containing mesoporous silicas, such as molecular dispersion [10,11], grafting [12][13][14] and impregnation [15][16][17]. These post-synthesis methods, in general, incorporate titanium species both in the pore channel and on the external surface of mesoporous silicas.…”

Section: Introductionmentioning

confidence: 99%

Post-synthesis of TiO2 Dispersed Inside the Pore Channels of SBA-15 and its Photocatalytic Activity for the Degradation of Methylene Blue

Shindo

Koizumi

Hatakeyama

et al. 2011

Int.J.Soc.Mater.Eng.Resour.

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TiO 2 -SBA-15 mesoporous materials in which titanium oxide species were dispersed inside the pore channels of SBA-15 were prepared by a novel post-synthesis method. In this method, cetyltrimethylammonium bromide surfactant molecules were incorporated inside the channels of the mesopores of SBA-15 followed by the addition of titanium tetraethoxide. Effect of hydrolysis conditions of titanium tetraethoxide on the formation and properties of Ti oxides in TiO 2 -SBA-15 materials was investigated. Physico-chemical properties of TiO 2 -SBA-15 materials were characterized by XRD, N 2 adsorption, SEM and UV-vis. Size and morphology of Ti oxide species in TiO 2 -SBA-15 materials were dependent on the hydrolysis conditions of titanium tetraethoxide, i.e., H 2 O/Ti molar ratio. Dispersed titanium oxide species were mainly formed on the internal surface of SBA-15, i.e., on the surface of mesopore walls of the TiO 2 -SBA-15 samples when synthesized at low H 2 O/Ti ratios of 2 and 4, whereas large TiO 2 anatase particles were predominantly formed on the external surface of SBA-15 when the samples were prepared at high H 2 O/Ti molar ratios. The photocatalytic activity of the TiO 2 -SBA-15 samples was investigated for the degradation of methylene blue, MB, and compared with that of pure TiO 2 , P25. The TiO 2 -SBA-15 samples, in which titanium oxide species were dispersed on the internal surface of SBA-15, showed higher and more stable photocatalytic activity in the degradation and/or decolorization of MB than P25 and TiO 2 -SBA-15 which has TiO 2 particles on the outer surface of SBA-15.

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Characterization of Vanadium and Titanium Oxide Supported SBA-15

Cited by 55 publications

References 27 publications

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

Hydration effects on the molecular structure of silica-supported vanadium oxide catalysts: A combined IR, Raman, UV–vis and EXAFS study

The mechanism for the controlled synthesis of highly dispersed vanadia supported on silica SBA-15

Post-synthesis of TiO2 Dispersed Inside the Pore Channels of SBA-15 and its Photocatalytic Activity for the Degradation of Methylene Blue

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