Effect of additives on properties of V2O5/SiO2 and V2O5/MgO catalysts

Klisińska, A.; Samson, K.; Gressel, I.; Grzybowska, B.

doi:10.1016/j.apcata.2006.04.028

Cited by 70 publications

(13 citation statements)

References 42 publications

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“…Considerable attention has been paid to the development of catalysts with high selectivity to propylene in the ODH. A V/MgO system was found to be one of the best in terms of activity and performance stability [2][3][4].…”

Section: Introductionmentioning

confidence: 97%

Nanocrystalline aerogel VOx/MgO as a catalyst for oxidative dehydrogenation of propane

Mishakov

Ilyina

Bedilo

et al. 2009

React Kinet Catal Lett

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Section: Introductionmentioning

confidence: 97%

Nanocrystalline aerogel VOx/MgO as a catalyst for oxidative dehydrogenation of propane

Mishakov

Ilyina

Bedilo

et al. 2009

React Kinet Catal Lett

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“…Metal oxides containing vanadium atoms are among the most important catalysts for oxidative dehydrogenation (ODH) of light alkanes . These oxides have been prepared and studied in diverse forms with vanadium-oxo species dispersed on nonreducible or reducible oxides, − are present as cations formed by replacing protons in aluminosilicates − or incorporated within the ordered framework of crystalline oxides, − and exhibit varying structural, electronic, and catalytic properties. Many vanadium-containing oxides show significant selectivity to C 2 H 4 in C 2 H 6 oxidative conversions.…”

Section: Introductionmentioning

confidence: 99%

Effects of Lattice O Atom Coordination and Pore Confinement on Selectivity Limitations for Ethane Oxidative Dehydrogenation Catalyzed by Vanadium-Oxo Species

2019

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M1-phase MoVTeNb mixed oxides contain V-oxo species isolated by dispersion in the Mo-oxo framework and one-dimensional heptagonal micropores that tightly enclose C2H6 molecules. These oxides catalyze C2H6 oxidation with C2H4 selectivity much higher than V2O5 oxides containing continuous V-oxo domains without micropores. Here, effects of the structures of VO x domains and of the micropores on the selectivity are discerned using (i) measured rate constant ratios and activation barrier differences relevant to selectivity on the two oxides and (ii) density functional theory (DFT) analysis of steps mediating C–H activation in C2H6 and C2H5 radicals and unselective C–O bond formations in C2H5 radicals and C2H4 molecules on (001) surfaces of both oxides and in pores of MoVTeNb oxides. The DFT-derived values of kinetic parameters representing C2H4 selectivities and activation energy differences between C2H4 formation and C–O bond formation steps on V2O5(001) are similar to measured values. In contrast, for MoVTeNb oxides, the DFT-derived selectivity inside the pores is much higher than measurements, while that on the (001) surfaces is much lower, suggesting that measured selectivity represents contributions from C–H activations inside the pores and unselective steps inside pores as well as on (001) surfaces. The selectivity on (001) surfaces is similar in V2O5 and MoVTeNb oxides, indicating that the isolation of V-oxo domains within this surface leads to only small changes in selectivity, while the pores lead to much higher selectivity. The descriptors of the selectivity trends on such transition metal oxide surfaces are derived by examining C2H4 epoxidation and C2H6 C–H activation transition-state energies and molecule-surface van der Waals (vdW) interactions and steric forces that influence these energies on a variety of O atoms with different electronic and structural properties on (001) surfaces and inside the pores. High C2H4 selectivity requires that the O atoms in oxides exhibit lower tendency to form C–O bonds in C2H4 than to activate C–H bonds in C2H6, which depends strongly on the H atom addition energies of oxides and O atom coordination. V2–O–V tri-coordinated and V–O–V or V–O–Mo bridging O atoms require significantly greater energy penalty than VO terminal O atoms for the metal–oxygen framework distortions required for forming C–O bonds; these distortion energies reflect steric hindrance to forming C–O bonds, which leads to higher epoxidation transition-state energy and indicates higher C2H4 selectivity in tri-coordinated and bridging O atoms. The high selectivity inside the heptagonal pores originates from the inaccessibility to terminal O atoms in addition to much stronger vdW interactions and more significant steric distortion energies in tight pores. These analyses suggest that H atom addition energies, vdW interaction energies, and catalyst distortion energies are relevant descriptors of selectivity for both intrapore and external O atoms.

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“…The measured propane conversions are below 40%. Such rather low conversions are typical for the ODH process-see, e.g., [29,33]. Figure 7 shows the relation between the catalytic performance (C3H8 conversion and C3H6 selectivity) and the contact time, taking as the example the V6.0FAUdes sample.…”

Section: Determination Of the Catalytic Properties In The Oxidative Dmentioning

confidence: 97%

Oxidative Dehydrogenation of Propane over Vanadium-Containing Faujasite Zeolite

et al. 2020

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Oxidative dehydrogenation (ODH) of light alkanes to olefins-in particular, using vanadium-based catalysts-is a promising alternative to the dehydrogenation process. Here, we investigate how the activity of the vanadium phase in ODH is related to its dispersion in porous matrices. An attempt was made to synthesize catalysts in which vanadium was deposited on a microporous faujasite zeolite (FAU) with the hierarchical (desilicated) FAU as supports. These yielded different catalysts with varying amounts and types of vanadium phase and the porosity of the support. The phase composition of the catalysts was confirmed by X-ray diffraction (XRD); low temperature nitrogen sorption experiments resulted in their surface area and pore volumes, and reducibility was measured with a temperature-programmed reduction with a hydrogen (H 2 -TPR) method. The character of vanadium was studied by UV-VIS spectroscopy. The obtained samples were subjected to catalytic tests in the oxidative dehydrogenation of propane in a fixed-bed gas flow reactor with a gas chromatograph to detect subtract and reaction products at a temperature range from 400-500 • C, with varying contact times. The sample containing 6 wt% of vanadium deposited on the desilicated FAU appeared the most active. The activity was ascribed to the presence of the dispersed vanadium ions in the tetragonal coordination environment and support mesoporosity.

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Effect of additives on properties of V2O5/SiO2 and V2O5/MgO catalysts

Cited by 70 publications

References 42 publications

Nanocrystalline aerogel VOx/MgO as a catalyst for oxidative dehydrogenation of propane

Nanocrystalline aerogel VOx/MgO as a catalyst for oxidative dehydrogenation of propane

Effects of Lattice O Atom Coordination and Pore Confinement on Selectivity Limitations for Ethane Oxidative Dehydrogenation Catalyzed by Vanadium-Oxo Species

Oxidative Dehydrogenation of Propane over Vanadium-Containing Faujasite Zeolite

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