Restructuring of silica supported vanadia during propane oxidative dehydrogenation studied by combined synchrotron radiation based in situ soft X-ray absorption and photoemission

Hävecker, Michael; Düngen, Pascal; Buller, Saskia; Knop‐Gericke, Axel; Trunschke, Annette; Schlögl, Robert

doi:10.1080/2055074x.2017.1287535

Cited by 5 publications

(2 citation statements)

References 38 publications

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“…The analysis of V L-edge presented above suggests that the V 5+ species on CoVO x catalysts are not octahedrally coordinated as expected for V 2 O 5 bulk oxide, but tetrahedrally. However, the shape and position of the photoemission and absorption spectra of CoVO x do not exactly match neither with two-dimensional vanadium oxides , nor with octahedral cobalt vanadate compounds (e.g., Co 3 V 2 O 8 ) ,,, and therefore do not allow a direct and unambiguous identification of the arrangement at the interface in our case.…”

Section: Discussionmentioning

confidence: 63%

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

et al. 2021

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Preferential oxidation of CO (COPrOx) is a catalytic reaction targeting the removal of trace amounts of CO from hydrogen-rich gas mixtures. Non-noble metal catalysts, such as Cu and Co, can be equally active to Pt for the reaction; however, their commercialization is limited by their poor stability. We have recently shown that CoO is the most active state of cobalt for COPrOx, but under certain reaction conditions, it is readily oxidized to Co3O4 and deactivates. Here, we report a simple method to stabilize the Co 2+ state by vanadium addition. The V promoted cobalt catalyst exhibits considerably higher activity and stability than pure cobalt. The nature of the catalytic active sites during COPrOx was established by operando NAP-XPS and NEXAFS, while the stability of the Co 2+ state on the surface was verified by in situ NEXAFS at 1 bar pressure. The active phase consists of an ultra-thin cobalt-vanadate surface layer, containing tetrahedral V 5+ and octahedral Co 2+ cations, with an electronic and geometric structure that is deviating from the standard mixed bulk oxides. In addition, V addition helps to maintain the population of Co 2+ species involved in the reaction, inhibiting carbonate species formation that are responsible for the deactivation. The promoting effect of V is discussed in terms of enhancement of CoO redox stability on the surface induced by electronic and structural modifications. These results demonstrate that V-promoted cobalt is a promising COPrOx catalyst and validate the application of in situ spectroscopy to provide the concept for designing better performing catalysts.

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Section: Discussionmentioning

confidence: 63%

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

et al. 2021

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“…For disordered vanadium oxides, such as powder and polycrystalline samples, the structure of the L 3 edge is less distinct [ 51 ], which is the case of desilicated V-HY deSi zeolite ( Figure 1 B). The O-K-edge spectrum region below 535 eV is determined by O-V bonding [ 52 ]. The lines at 529.5 eV and 532 eV correspond to the electronic transitions from the O 1s core to the O 2p–V 3d(t 2g ) and O 2p–V 3d(e g ) states, respectively [ 53 ].…”

Section: Resultsmentioning

confidence: 99%

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites

Smoliło-Utrata

Tarach

Samson

et al. 2022

IJMS

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The commercially available zeolite HY and its desilicated analogue were subjected to a classical wet impregnation procedure with NH4VO3 to produce catalysts differentiated in acidic and redox properties. Various spectroscopic techniques (in situ probe molecules adsorption and time-resolved propane transformation FT-IR studies, XAS, 51V MAS NMR, and 2D COS UV-vis) were employed to study speciation, local coordination, and reducibility of the vanadium species introduced into the hierarchical faujasite zeolite. The acid-based redox properties of V centres were linked to catalytic activity in the oxidative dehydrogenation of propane. The modification of zeolite via caustic treatment is an effective method of adjusting its basicity—a parameter that plays an important role in the ODH process. The developed mesopore surface ensured the attachment of vanadium species to silanol groups and formation of isolated (SiO)2(HO)V=O and (SiO)3V=O sites or polymeric, highly dispersed forms located in the zeolite micropores. The higher basicity of HYdeSi, due to the presence of the Al-rich shell, aided the activation of the C−H bond leading to a higher selectivity to propene. Its polymerisation and coke formation were inhibited by the lower acid strength of the protonic sites in desilicated zeolite. The Al-rich shell was also beneficial for anchoring V species and thus their reducibility. The operando UV-vis experiments revealed higher reactivity of the bridging oxygens V-O-V over the oxo-group V=O. The (SiO)3V=O species were found to be ineffective in propane oxidation when temperature does not exceed 400 °C.

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Structural Modification of Ru‐Bi Catalysts and its Impact on One‐Pot Synthesis of 2,3,5‐trimethyl‐1,4‐benzoquinone with Hydrogen Peroxide

Lekgetho,

Mabena,

Tukulula

et al. 2024

ChemistrySelect

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Oxidative transformation of phenols is an efficient route towards the production of moieties for naturally occurring quinones with a wide range of biological activities. Silica supported Ru−Bi catalysts were prepared by microwave‐assisted loading (MW) and deposition (DP) methods. The as‐prepared catalysts were characterized by XRD (X‐ray diffraction), N2 physisoption, SEM (Scanning electron microscopy), TEM (Transmission electron microscopy) and XPS (X‐ray photoelectron spectrometry) techniques. Catalysts with low Bi loading, 5 %Ru‐1 %Bi, have narrow particle size distributions that correspond to an average particle size of 2.21–2.59 nm. 5 %Ru‐5 %Bi catalysts consist of Ru−Bi nanochains. The outcome of the catalytic oxidation of 2,3,5‐trimethylhydroquinone (TMHQ, 1) to 2,3,5‐trimethyl‐1,4‐benzoquinone (TMBQ, 2) depends on the catalyst preparation method, promoter loading, solvent and temperature used. MW‐5Ru1Bi is the most active catalyst with conversions that range between 99–100 % at both room temperature (r.t) and under refluxing MeNO2 and MeOH. The highest yields of TMBQ (100 %) were obtained over MW‐5 %Ru‐1 %Bi and DP‐5 %Ru‐5 %Bi catalysts.

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Restructuring of silica supported vanadia during propane oxidative dehydrogenation studied by combined synchrotron radiation based in situ soft X-ray absorption and photoemission

Cited by 5 publications

References 38 publications

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

Improving the Catalytic Performance of Cobalt for CO Preferential Oxidation by Stabilizing the Active Phase through Vanadium Promotion

Modulation of ODH Propane Selectivity by Zeolite Support Desilication: Vanadium Species Anchored to Al-Rich Shell as Crucial Active Sites

Structural Modification of Ru‐Bi Catalysts and its Impact on One‐Pot Synthesis of 2,3,5‐trimethyl‐1,4‐benzoquinone with Hydrogen Peroxide

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