Direct correlation of the dispersion and structure in vanadium oxide supported on silica SBA-15

Heß, Christian

doi:10.1016/j.jcat.2007.02.024

Cited by 43 publications

(23 citation statements)

References 23 publications

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“…For the sample used here (0.7 V nm -2 ), no crystalline V 2 O 5 was observed with visible Raman spectroscopy [10]. By combining Raman spectroscopy, DR UV-Vis spectroscopy as well as X-ray photoelectron spectroscopy (XPS) we recently demonstrated the strong increase in the dispersion of the supported vanadia species upon dehydration [4]. The changes in the dispersion are accompanied by distinct structural changes, i.e., changes in the vanadium coordination as well as the size of the vanadia aggregates.…”

Section: Resultsmentioning

confidence: 85%

“…An interesting reaction for kinetic modelling is the oxidative dehydrogenation of propane (ODP) on supported vanadia catalysts [1][2][3]. Besides a great effort to describe these catalysts structurally [4][5][6] many studies tried to elucidate kinetics and mechanism of ODP [7][8][9]. A great disadvantage of all these studies is the lacking connection between kinetics and analytical characterisation, the so called structure-reactivity relationship.…”

Section: Introductionmentioning

confidence: 99%

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Oxidative dehydrogenation of propane on silica (SBA-15) supported vanadia catalysts: A kinetic investigation

Dinse

Khennache

Frank

et al. 2009

Journal of Molecular Catalysis A: Chemical

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Silica (SBA-15) supported vanadium oxide was used for a kinetic study of the oxidative dehydrogenation of propane in a fixed bed reactor. Prior to this study, spectroscopic characterization using a variety of techniques such as FTIR spectroscopy, Raman spectroscopy, DR UV-Vis spectroscopy and X-ray Phototelectron Spectroscopy revealed the absence of bulk vanadia and a high dispersion of active surface sites for the investigated catalyst. The kinetic data evaluation was based on a formal kinetic approach. Calorimetric measurements were used to determine the heat of adsorption of propane on the catalyst. The data indicate that the primary combustion of propane is negligible. Reaction orders of one for the propane dehydrogenation and propene combustion indicate the participation of these species in the respective rate determining step. The zero reaction order determined for the catalyst reoxidation reveals a participation of lattice oxygen in this reaction step. Higher activation energies of propane dehydrogenation as compared to the propene combustion indicate the participation of the weaker allylic C-H bond of propene in the rate determining step of the propene combustion. This results in higher propene selectivites at elevated temperatures. Kinetic parameters, including apparent and real activation energies and the equilibrium constant of the propane adsorption allowed for a comparison with theoretical predictions and show a good agreement.

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Section: Resultsmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Oxidative dehydrogenation of propane on silica (SBA-15) supported vanadia catalysts: A kinetic investigation

Dinse

Khennache

Frank

et al. 2009

Journal of Molecular Catalysis A: Chemical

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“…These are: the M1 phase, two species of grafted vanadium oxide on silica as SBA 15 [113] and on the same mesoporous system pre-covered with amorphous titanium oxide. These two species contain monomeric and low oligomeric sites of vanadia in pentavalent states [114,115]. Whereas on SBA a non-reducible support would represent electronically isolated species, the amorphous titania ad layer represents a prototype of reducible support to which the vanadia does form chemical bonds and does exchange [116] electrons.…”

Section: Active Sites For Odpmentioning

confidence: 99%

Active Sites for Propane Oxidation: Some Generic Considerations

Schlögl

2011

Top Catal

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Based on experimental observations about structure and dynamics of the reactive surface of the M1 phase some considerations are made about the nature and size of active sites. In analyzing the stoichiometry of the reactions following activation of propane it occurs that for dehydrogenation small sites are desirable being just sufficient to re-activate oxygen without kinetic hindrance. For deeper oxidation to acrylic acid (AA) the sites should be larger to accommodate all redox equivalents and oxygen species required for one transformation. A qualitative model for size and composition of the active site is made. It is likely that the active site consists on a VxOy species of strictly 2-D nature. This follows the structural suggestion for the active site on the a-b-plane of the M1 structure. The role of Te in moderating the active site is discussed. The suggestions are discussed in comparing requirements for oxidative dehydrogenation of propane (ODP) with those for AA synthesis.

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“…[22][23][24][25] Hydrated vanadia species on silica consist of layers of polymerized vanadia with the transition metal in pseudo-octahedral coordination. [22] A water molecule is bound to about every second vanadium atom in a fully hydrated sample.…”

Section: Spectroscopic Characterization Of the Supported Vanadia Speciesmentioning

confidence: 99%

Role of dispersion of vanadia on SBA-15 in the oxidative dehydrogenation of propane

et al. 2010

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A series of vanadia catalysts supported on the mesoporous silica SBA-15 are synthesized using an automated laboratory reactor. The catalysts contain from 0.6 up to 13.6V atoms/nm 2 and are structurally characterized by various techniques (BET, XRD, SEM, TEM, Raman, IR, UV/Vis).Samples containing up to 3.1V/nm 2 are structurally rather similar. They all contain a mixture of tetrahedral (VOx)n species, both monomeric and oligomeric. The ratio of monomeric and oligomeric species depends on the vanadia loading. At the highest loading of 13.6V/nm 2 , in addition to tetrahedral (VOx)n, also substantial amounts of three-dimensional, bulk-like V2O5 are present in the catalyst. The structural similarity of the lowloaded catalysts is reflected in their alike catalytical activity during the oxidative dehydrogenation (ODH) of propane between 380 and 480 °C. Propene, CO, and CO2 are formed as reaction products, while neither the formation of ethene nor acrolein or acrylic acid is observed in other than trace amounts. The activation energy for ODH of propane is 140 kJ/mol. The catalyst with the highest loading yields varying activation energies for different reaction conditions, which is probably related to rearrangements between bulk-like and dispersed, two-dimensional (VOx)n. Rather than the monomer to oligomer ratio, the ratio of two-dimensional to three-dimensional vanadia seems to be crucial for the catalytic properties of silica supported vanadia in the ODH of propane.

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Direct correlation of the dispersion and structure in vanadium oxide supported on silica SBA-15

Cited by 43 publications

References 23 publications

Oxidative dehydrogenation of propane on silica (SBA-15) supported vanadia catalysts: A kinetic investigation

Oxidative dehydrogenation of propane on silica (SBA-15) supported vanadia catalysts: A kinetic investigation

Active Sites for Propane Oxidation: Some Generic Considerations

Role of dispersion of vanadia on SBA-15 in the oxidative dehydrogenation of propane

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