Effects of Excitation Wavelength on the Raman Spectra of Vanadium(V) Oxo Compounds

Panitz, Jan‐Christoph; Wokaun, Alexander

doi:10.1021/jp961923c

Cited by 7 publications

(7 citation statements)

References 32 publications

(59 reference statements)

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“…Consequently, they are not resonantly enhanced. We assign the first two bands to C–H deformation vibrations and the third band to a C–H stretching vibration, in agreement with the literature. ,− …”

Section: Discussionsupporting

confidence: 90%

“…Furthermore, the intensity of the combination band at 1151 cm –1 also decreases. In the literature, the Raman band located at 662 cm –1 in Figure a has been assigned to VO stretching vibrations of vanadium alkoxides. ,− Please note that in the time-resolved experiments discussed later this adsorbate-related band will also be referred to as ν c , which results from the fact that, owing to strong overlap, the Raman band of the metal oxide at 695 cm –1 cannot be deconvoluted from the adsorbate band at 662 cm –1 during fitting analysis.…”

Section: Resultsmentioning

confidence: 99%

“…The bands at 809 and 1460 cm –1 as well as the features around 2941 cm –1 belong to this category. In the literature, they are assigned to bending and stretching vibrations of the CH 2 /CH 3 groups of ethoxide, respectively. ,− …”

Section: Resultsmentioning

confidence: 99%

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Operando Multiwavelength and Time-Resolved Raman Spectroscopy: Structural Dynamics of a Supported Vanadia Catalyst at Work

2018

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A novel operando spectroscopic approach combining multiwavelength and time-resolved Raman spectroscopy with gasphase Fourier transform infrared (FTIR) spectroscopy is presented, supported by in situ UV−vis diffuse reflectance (DR) spectroscopy. The potential of this approach is demonstrated in a case study of the oxidative dehydrogenation (ODH) of ethanol over a silica-supported vanadia catalyst. The structural dynamics of the catalyst upon switching from oxidative to reactive conditions was extensively studied by Raman spectroscopy with different excitation wavelengths in the visible and UV, exploiting resonance effects in a targeted manner. Time-dependent correlation of Raman and IR spectra over several reaction cycles allows identification of active vanadia surface structures. Detailed Raman spectroscopic analysis reveals that the adsorption of ethoxy species onto dispersed VO x structures occurs via opening of both V−O−Si and V−O−V bonds. During reaction, large oligomeric VO x structures are decomposed into smaller units. Combined Raman and UV−vis results show that these structural changes cannot be completely regenerated.

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Section: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

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Operando Multiwavelength and Time-Resolved Raman Spectroscopy: Structural Dynamics of a Supported Vanadia Catalyst at Work

2018

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“…Intense band at 902 cm -1 observed in the Raman spectrum of the MIL-47(V) is caused by V IV =O group's stretching vibration [67]. The Raman spectrum of the intermediary VO(OiPr)3@MIL-101(Cr) exhibits intense band at 910 cm -1 accompanied by a few poorly distinguished bands in 1030-920 cm -1 region originating from the triisopropoxide moieties (most likely caused by O=V(-O-)n vibration [68]. The Raman spectrum of the VOx@MIL-101(Cr) sample after hydrolysis reveals that typical Raman bands of the MIL-101(Cr) support are preserved while the spectral features of the triisopropoxide moiety disappeared and new bands located at 1021 and 934 cm -1 , which are assigned to terminal V=O and bridging V-O-V vibrations [69] respectively, showed up in the spectrum.…”

Section: *-R Denotes Sample After Reaction Testmentioning

confidence: 99%

Efficient oxidative dehydrogenation of ethanol by VOx@MIL-101: On par with VOx/ZrO2 and much better than MIL-47(V)

et al. 2019

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The possibility to apply metal organic framework (MOF) based catalysts for oxidation reaction in gas phase was explored. Catalytic activity of the vanadium oxide catalyst incorporated in MIL-101(Cr) as support was investigated in gas phase ethanol oxidative dehydrogenation (EtOH-ODH) and compared to that of MIL-47(V) metal organic framework material containing vanadium as central metal in the framework structure and to a classical VOx/ZrO2 supported vanadium oxide catalyst. It was found that vanadium species, incorporated in MIL-101(Cr) support by a variant of vapor deposition method, are stabilized in the form of well dispersed VOx species (no vanadium pentoxide clusters was detected in the catalyst). The obtained VOx@MIL-101(Cr) catalyst exhibited high selectivity towards acetaldehyde (up to 99%) at reaction temperatures not exceeding 200°C. The catalytic activity of VOx@MIL-101(Cr) catalyst reached an activity level comparable to that of the classical VOx/ZrO2 catalyst, but the specific productivity of acetaldehyde (3 kgAA kgcat-1 h-1) was higher by 75% compared with productivity on VOx/ZrO2 due to much higher content of vanadium species, which could be hosted by the MOF. On the other hand, MIL-47(V) catalyst exhibited negligible activity seemingly due to coordinatively saturated character of the vanadium centers and/or too high stability of the V IV oxidation state. This proof-of-concept study proved that application of MOF materials as host matrices for heterogeneous catalysts aiming oxidation reaction in gas phase could be efficient as demonstrated on the example of oxidative dehydrogenation of ethanol.

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“…[10][11][12] Analysis of vanadium oxide layers on catalysts where the intensities ratios varies depending on the use of the 482.5 or 676.5 nm laser lines and vanadium type. 13 However, until now there has been scarce information in the literature on the Raman scattering analysis of MOs using different excitation wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Multiwavelength Raman Spectroscopic Analysis of Superficial Iron–Chromium Oxides Generated Using Laser Irradiation

et al. 2018

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In order to characterize iron-chromium oxides generated by laser irradiation on the surface of stainless steel plates, an ultraviolet-visible (UV-Vis) near-infrared (NIR) multiwavelength excitation Raman analysis has been performed using both austenitic SS304 and ferritic SS430 stainless steel samples. Raman spectra were obtained using five different excitation wavelengths from blue (455 nm) to NIR (830 nm). These measurements have allowed us to observe and identify four Raman bands, among which two have not been previously observed for iron-chromium oxides, and characterize the existence of different resonant excitation conditions for the different excitation wavelengths. For example, when using 455 nm as excitation wavelength the band at 485 cm did not show up, although that when using 830 nm as excitation wavelength is a clear characteristic band for iron-chromium oxide. In addition, the dependence of the spectra profile with the excitation wavelength for films and microspheres features was observed. This experimental Raman analysis shows the importance of the excitation wavelength for the characterization of metallic oxides with different features.

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Effects of Excitation Wavelength on the Raman Spectra of Vanadium(V) Oxo Compounds

Cited by 7 publications

References 32 publications

Operando Multiwavelength and Time-Resolved Raman Spectroscopy: Structural Dynamics of a Supported Vanadia Catalyst at Work

Operando Multiwavelength and Time-Resolved Raman Spectroscopy: Structural Dynamics of a Supported Vanadia Catalyst at Work

Efficient oxidative dehydrogenation of ethanol by VOx@MIL-101: On par with VOx/ZrO2 and much better than MIL-47(V)

Multiwavelength Raman Spectroscopic Analysis of Superficial Iron–Chromium Oxides Generated Using Laser Irradiation

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