Combined Raman and IR study of MOx–V2O5/Al2O3(MOx= MoO3, WO3, NiO, CoO) catalysts under dehydrated conditions

Vuurman, Michael A.; Stufkens, Derk J.; Oskam, A.; Deo, Goutam; Wachs, Israel E.

doi:10.1039/ft9969203259

Cited by 115 publications

(63 citation statements)

References 47 publications

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“…9, 49,[87][88][89][90] Moreover, the ambiguity in the assignment of the Raman bands of CoO has recently been reported. 91 Similarly, the interpretation of Raman spectra of the well-known compound wüstite (FeO) is still unclear.…”

Section: Specular Reflectance Uv-vis-nir Spectrophotometrymentioning

confidence: 99%

Optical and Physical Properties of Cobalt Oxide Films Electrogenerated in Bicarbonate Aqueous Media

2006

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For the first time, cobalt oxide films that are highly protective against localized corrosion and depicting a wide variety of bright and uniform colors due to light interference, have been successfully electrogenerated on polycrystalline cobalt disk electrodes under potentiostatic polarization in a mild aqueous bicarbonate medium. Open circuit potential measurements have shown the formation of a film with a bilayered structure, organized as a thin Co 3 O 4 outer layer and a thick CoO inner layer. The existence of Co 3 O 4 as a thin outer layer, previously postulated from galvanostatic reduction experiments, has been confirmed from XPS analysis. Raman spectroscopy, performed using a very low laser intensity, has shown that the films are mainly composed of CoO. The broadness of the Raman bands observed is associated to the amorphous character of the film, a result that has been confirmed by spectroscopic ellipsometry and X-ray diffraction analysis. Overall film thicknesses, well controlled by the anodization duration, were determined and correlated using mechanical (atomic force microscopy and profilometry) and spectroscopic (specular UV-vis-NIR reflectance and ellipsometry) techniques. Spectroscopic ellipsometry, using a simple amorphous dispersion model, has proved efficient for measuring thicknesses of films ranging from 31 to 290 nm with very low standard deviations. The real part of the complex refractive indices of these films, ranging from 1.8 to 2.2 (at λ ) 632.8 nm) depending on the anodization duration, is in good agreement with values reported in the literature for CoO. The film with the highest refractive index, and consequently the more densely packed structure, was obtained following a 30-minute anodization period.

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Section: Specular Reflectance Uv-vis-nir Spectrophotometrymentioning

confidence: 99%

Optical and Physical Properties of Cobalt Oxide Films Electrogenerated in Bicarbonate Aqueous Media

2006

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“…Instead of the absorption band of the ν(-Ti-O) stretching mode, there was a broad band at 750 cm -1 seemingly indicating severe distortion of the titanium-oxygen octahedron in the structures of the forming compounds 31,32 . In addition, the spectra of the samples shown in Figure 3 revealed a band at around 2000 cm -1 which was assigned to the V=O bond overtone vibration 33 . The intensity of the overtone band might be predicted to be continuously increased with an enhanced vanadia loading.…”

Section: Catalyst Characterization Resultsmentioning

confidence: 99%

Physicochemical Properties and Catalytic Performances of Nanostructured V2O5 over TiO2 and γ-Al2O3 for Oxidative Dehydrogenation of Propane

Kazemeini

Nikkhah

Fattahi

et al. 2016

Chem.Biochem.Eng.Q.

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Samples of V 2 O 5 catalysts supported on nanostructures of TiO 2 and γ-Al 2 O 3 were synthesized through the hydrothermal method and used for the oxidative dehydrogenation of propane (ODHP) to propylene. The TiO 2 support was utilized in both commercial microstructure and synthesized nanostructure forms. Moreover, the γ-Al 2 O 3 support was synthesized through chemical and precipitation methods. The vanadium catalyst was then deposited onto the hybrid of the TiO 2 and γ-Al 2 O 3 materials. All prepared catalysts were characterized through the BET, FESEM, FTIR, XRD and TPR techniques. Performances of the synthesized catalysts were subsequently examined in a fixed-bed reactor. The main products were propylene, ethylene and CO x . The prepared catalysts over TiO 2 and γ-Al 2 O 3 were evaluated under reactor test conditions of 500 °C, feed of C 3 H 8 /air with molar ratio of 0.6, and total feed flow rate of 90 mL min -1 . These resulted in optimum values of 35.53 and 23.88 % for the propylene selectivity and propane conversion, respectively 6 h after the start of the reaction. The comparison of performances made between the synthesized materials and those available in the open literature for the ODHP reaction was indeed satisfactory.

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“…Many authors have used a solution of VOCl 3 in CCl 4 or in benzene to obtain a dispersed VO x phase on various inorganic oxides [149]. Non-aqueous solutions of VO(O i Bu) 3 have also been successfully used [150][151][152][153]. Multiple grafting followed by calcination will result in a monolayer of vanadium oxides on the surface of a support oxide.…”

Section: Preparation Methods Of Supported Vanadium Oxide Catalystsmentioning

confidence: 99%

Chemistry, Spectroscopy and the Role of Supported Vanadium Oxides in Heterogeneous Catalysis

Weckhuysen

Keller

2003

ChemInform

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Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular structure of vanadium in water and in the solid state and an overview of the spectroscopic techniques enabling to study the chemistry of supported vanadium oxides. In the second part, it will be shown that advanced spectroscopic tools can be used to obtain detailed information about the coordination environment and oxidation state of vanadium oxides during each stage of the life-span of a heterogeneous catalyst. Three topics will be discussed: (1) the molecular structure of supported vanadium oxide catalysts under hydrated, dehydrated and reduced conditions, including the parameters, which influence the molecular structures formed at the surface of the support oxide; (2) elucidation of the active surface vanadium oxide during the oxidation of methanol to formaldehyde, the reaction mechanism and the vanadium oxide-support effect; and (3) deactivation of fluid catalytic cracking (FCC) catalysts by migration of vanadium oxides and the development of a method preventing the structural breakdown of zeolites by trapping the mobile vanadium oxides in an aluminum oxide coating.

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Combined Raman and IR study of MO_x–V₂O₅/Al₂O₃(MO_x= MoO₃, WO₃, NiO, CoO) catalysts under dehydrated conditions

Cited by 115 publications

References 47 publications

Optical and Physical Properties of Cobalt Oxide Films Electrogenerated in Bicarbonate Aqueous Media

Optical and Physical Properties of Cobalt Oxide Films Electrogenerated in Bicarbonate Aqueous Media

Physicochemical Properties and Catalytic Performances of Nanostructured V2O5 over TiO2 and γ-Al2O3 for Oxidative Dehydrogenation of Propane

Chemistry, Spectroscopy and the Role of Supported Vanadium Oxides in Heterogeneous Catalysis

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