Structure Of Vanadium Oxide Research Articles

Metal–promoter interactions in vanadium oxide promoted Rh/SiO2catalysts

The influence of the calcination temperature on the structure and morphology of vanadium oxide promoted, silica-supported rhodium catalysts was studied. Pure Rh/SiO2 and VOx/SiO2 served as reference systems. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), FTIR spectroscopy of adsorbed CO and BET surface-area measurements. BET, XRD and TEM investigations revealed a strong sintering of the silica support at calcination temperatures at and above 973 K. There is a crystalline silica phase, which was found exclusively in the promoted Rh/SiO2 catalyst calcined at 1173 K. XRD, TPR and TEM gave evidence for the formation of rhodium–Vanadium mixed oxide on the catalyst surface at 973 K calcination. After high-temperature reduction (HTR = 773 K) highly dispersed metal is formed from this ternary oxide phase. A C- and O-bonded carbonyl species probably located at the metal/promoter interface was detected by FTIR spectroscopy at 83 K.

ChemInform Abstract: Structure and Acidity of Vanadium Oxide Layered on Titania (Anatase and Rutile).

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

FTIR investigation of the structure of vanadium oxides on ZrO2 and oxidation of toluene on it

The oxidation of toluene has been studied on V2O5/ZrO2 by both FTIR spectroscopy and pulse method. The results suggest that Lewis-acidic sites play a significant role in the formation of benzaldehyde from toluene.

Structure and acidity of vanadium oxide layered on titania (anatase and rutile)

The adsorption of pyridine on, and the structure of, two series of V2O5/TiO2(anatase and rutile) samples, prepared by the gas-phase method (1.2–3.4 wt.%), have been studied. V–Ti oxides show both Brønsted- and Lewis-acidic sites. The Brønsted sites increases with increasing vanadium loadings. The number of Lewis sites on the anatase samples is greater than on the rutile form. From Raman and in situ FTIR studies the vanadium oxides on both series are composed mainly of surface vanadia species. These are stable during heat treatment at 673 K. The VO character of a monolayer rutile sample is different from that of a monolayer anatase sample, and resembles that of multilayer samples.

Structure of vanadium oxides on ZrO2 and the oxidation of butene

The oxidation of butene on V–Zr oxides prepared by the gas-phase and the impregnation method has been studied by F.t.i.r. spectroscopy as well as the microcatalytic method. V–Zr catalysts above 6.0 wt % vanadium loading show almost constant activity. V–Zr catalysts at low vanadium loadings show high selectivities to furan and buta -1.3-diene, while high vanadium loading catalysts show high selectivities to acetaldehyde and acetic acid. The formation of a dihydrofuran-like intermediate before the formation of furan has been proposed. The oxyhydrative scission mechanism is proposed in the formation of acetaldehyde and acetic acid. This formation is attributed to the presence of Brønsted acidity.

ChemInform Abstract: Quantum Chemical Study of Metal Oxide Catalysts. Structures of Vanadium Oxide and Niobium Oxide Clusters Supported on Silica and Alumina

Abstractas well as the unsupported catalysts are investigated by using the ab initio MO method.

Quantum chemical study of metal oxide catalysts: structures of vanadium oxide and niobium oxide clusters supported on silica and alumina

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantum chemical study of metal oxide catalysts: structures of vanadium oxide and niobium oxide clusters supported on silica and aluminaHisayoshi Kobayashi, Masaru Yamaguchi, Tsunehiro Tanaka, Yasuo Nishimura, Hiroshi Kawakami, and Satohiro YoshidaCite this: J. Phys. Chem. 1988, 92, 9, 2516–2520Publication Date (Print):May 1, 1988Publication History Published online1 May 2002Published inissue 1 May 1988https://doi.org/10.1021/j100320a025RIGHTS & PERMISSIONSArticle Views132Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (617 KB) Get e-Alerts

ChemInform Abstract: Surface Structure and Reactivity of Vanadium Oxide Supported on Titanium Dioxide. V2O5/TiO2 (Rutile) Catalysts Prepared by Hydrolysis.

AbstractV‐Ti‐O catalysts of different V2O5 content are prepared by hydrolysis of V(IV)‐Ti(IV) solutions and low‐temp.

Surface structure and reactivity of vanadium oxide supported on titanium dioxide. V2O5/TiO2(rutile) Catalysts prepared by Hydrolysis

V–Ti–O (rutile) catalysts have been prepared by hydrolysis of VIV–TiIV solutions and low-temperature calcination (673 K). The catalysts were characterized by chemical analyses, X.r.d., e.s.r. and F.t.i.r. spectroscopies, and thermogravimetry and tested in the oxidation of o-xylene to phthalic anhydride and in the ammoxidation of toluene to benzonitrile. Different vanadia species were identified: (i) a VIV species present in substitutional solid solution within the rutile lattice, which is stable as regards both oxidation and reduction, (ii) a VV species, chemically interacting with the rutile surface and constituting the so-called monolayer which is easily reducible to VIV, (iii) surface VO2+ ions formed by reduction during the catalytic tests from the VV monolayer species and (iv) highly disordered and poorly crystalline V2O5. The VO2+ surface ions formed during the catalytic tests are thought to be the active sites of hydrocarbon activation during both oxidation and ammoxidation. A modification of the chemical structure occurs during permanence in the reaction environment, this modification depending on the reductive power of the gas phase. In the case of the ammoxidation of toluene a change in the relative amounts of the different vanadia species occurs, while in the case of o-xylene oxidation only an higher average degree of reduction is observed, as compared to the samples before reaction. A comparison with V–Ti–O (anatase) samples suggests that the crystalline structure of TiO2 does not influence the activity of the V–Ti–O catalysts, but possibly the number of surface VO2+ ions does, and is strongly related to the method of preparation and to the activation procedure.

Structure of vanadium oxide on supports as measured by the benzaldehyde-ammonia titration method

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure of vanadium oxide on supports as measured by the benzaldehyde-ammonia titration methodMiki. Niwa, Yoshihito. Matsuoka, and Yuichi. MurakamiCite this: J. Phys. Chem. 1987, 91, 17, 4519–4524Publication Date (Print):August 1, 1987Publication History Published online1 May 2002Published inissue 1 August 1987https://doi.org/10.1021/j100301a020RIGHTS & PERMISSIONSArticle Views125Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (724 KB) Get e-Alerts

Fourier-transform infrared investigation of structures of vanadium oxide on various supports

Surface structures of vanadium oxides supported on various metal oxides (titania, alumina, zirconia and silica gel) formed by wet impregnation and by gas-phase preparation have been studied by Fourier-transform infrared spectroscopy. The V content ranged from 1.4 to 12 wt %. The application of band-shape analysis to the severely overlapped and weak bands using a small computer system has provided quantitative information for the surface vanadates. The surface vanadium oxides on titania are composed of three species. On catalysts prepared by the gas-phase method a new phase of vanadate is observed in i.r. spectra. The surface vanadates vary with the preparation methods as well as the repeat time of VOCl3 circulation.

An ab initio MO calculation on the structures of vanadium oxide and niobium oxide clusters supported on silica and alumina.

Geometrical structures of vanadium oxide and niobium oxide clusters supported on silica and alumina are investigated by means of ab initio molecular orbital method. Optimized geometries are searched using the energy gradient technique. For the clusters supported on silica and alumina, mono-oxo and di-oxo structures are more stable respectively. Stabilization of the di-oxo structure is ascribed to the bond formation between the oxygen and aluminum atoms in the cluster. Bond lengths estimated by the above calculations are 1.56A (1.77A) and 1.58A (1.95A) for V-O double (single) bond on silica and alumina, respectively, and 1.72A (1.92A) and 1.73A (2.11A) were obtained for Nb-O double (single) bond. Calculated values are compared with available data from EXAFS measurements, and good agreement, as a whole, is given for the systems examined here.

Loss functions and electronic structure of titanium and vanadium oxides

The relations between the optical reflectivity data and the electron-energy-loss spectra of the transition metal oxides, titanium oxides (TiO 2, Ti 2O 3) and vanadium oxides (VO 2, V 2O 3), have been investigated. Our results are in agreement with predictions of the energy band model based on the study of insulator-to-metal transitions in some of these oxides, and provide a useful check of the interpretation of the recent electron-energy-loss spectra obtained by Henrich for bulk titanium oxide (Ti 2O 3) and titanium oxide (TiO 2) surface reduced by argon ion bombardment.

X-ray emission spectra and quantum chemical calculations of electronic structure of vanadium oxides

Electronic structure calculations for clusters in VO, V 2O 3, VO 2, and V 2O 5 have been carried out by the Mulliken-Wolfsberg-Helmholtz method with self-consistency on charges and configurations. The results of the calculations agree quite well with available experimental data and allow us to give a complete interpretation of X-ray emission and ESCA spectra. The effective charges and electron configurations for vanadium atoms in oxides have been obtained and chemical bonding effects are discussed.