Molybdenum oxide supported on nanostructured MgO: Influence of the alkaline support properties on MoOx structure and catalytic behavior in selective oxidation

Scholz, Juliane; Walter, Anke; Hahn, Alexander; Ressler, Thorsten

doi:10.1016/j.micromeso.2013.05.032

Cited by 21 publications

(14 citation statements)

References 42 publications

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“…[16,38,39] For instance, mainly isolated [MoO 4 ]u nits existed on an alkaline MgO support, whichw as in agreement with the behavior of molybdenumo xidesi nt he alkaline solution. [24] Herein, the acidic surface of silica SBA-15 resulted in mainly linked MÀOÀM( M=Mo, V) species, which was again in agreement with the behavior of vanadates and molybdates in acidic solutions. [40,41] …”

supporting

confidence: 77%

“…It was shown earlier that highly polymerized [VO x ]a nd [MoO x ]s peciess howed an increased selectivity toward oxidationproducts. [24,42] In addition, the majority of [ [24,42] Effect of Ps pecies on catalyticactivity P-containing catalysts (i.e.,VPO, FePO, and MoPO) play acrucial role as oxidation catalysts. [7] Addings malla mountso fp hos- www.chemcatchem.org phoric acidt ot he feed showed positive effects on long-term stabilitya nd catalytic performance of FePO catalysts during the ODH of isobutyric acid to methacrylic acid.…”

Section: Catalytic Performancementioning

confidence: 99%

“…[18,23] For am ore detailed analysis, hexagonal MoO 3 was used as astructuralmodel.Theoretical X-ray absorption fine structure (XAFS) phases and amplitudes were calculated for MoÀOa nd MoÀMo distances and used fore xtended X- Hence, isolated tetrahedral [MoO 4 ]u nits can be excluded as major molybdenum oxide species. [24] Linear combinations of the XANES spectra of Na 2 The evolution of the average local structure aroundVc enters in the supported catalysts and reference materials differed from that aroundM oc enters. The VK -edge FT(c(k)·k 3 )o fa ctivated V 2 Mo 10 O x -SBA-15 and activated PV 2 Mo 10 -SBA-15 is shown in Figure 7.…”

mentioning

confidence: 99%

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Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

2015

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Vanadium‐containing Keggin‐type heteropolyoxo molybdate ([PV2Mo10O40]5−) was supported on silica SBA‐15 (denoted as PV2Mo10‐SBA‐15). The structural evolution and catalytic activity of PV2Mo10‐SBA‐15 and a suitable reference V2Mo10Ox‐SBA‐15 were investigated under selective propene oxidation conditions by using in situ X‐ray absorption spectroscopy. 31P MAS NMR measurements of supported PV2Mo10‐SBA‐15 and reference H3PO4‐SBA‐15 were performed after the catalytic reaction. PV2Mo10‐SBA‐15 formed a mixture of mainly tetrahedral [MoOx] and [VOx] units during thermal treatment under propene oxidation conditions. Changes in the average local structure around V centers coincided with the changes in the average local structure around Mo centers and the onset of catalytic activity. In addition, mainly tetrahedral [MoOx] and [VOx] units seemed to be in close proximity and interacted under catalytic conditions. Conversely, in the reference material V2Mo10Ox‐SBA‐15 synthesized with individual V and Mo source precursors, Mo and V centers appeared to be more separated from each other. The structural environment of P in PV2Mo10‐SBA‐15 under catalytic conditions corresponded to a mixture of various species. P was connected to both the support material SBA‐15 via POSi bonds and [MoOx] or [VOx] units. Apparently, the proximity of V and Mo in Keggin precursors was a prerequisite for obtaining (Mo,V) oxide species on the support material.

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confidence: 77%

Section: Catalytic Performancementioning

confidence: 99%

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confidence: 99%

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Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

2015

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“…Absorption edge energies were determined according to a method described elsewhere . Shape and size of particles as well as structural motifs can be deduced from the obtained absorption edge energies . Nanometer scale particles show quantum size effects which lead to a relationship between particle size and absorption edge energies ,.…”

Section: Resultsmentioning

confidence: 99%

Correlation between Copper Oxide Particle Size and Selectivity towards Propylene Oxide in Selective Oxidation of Propene

et al. 2018

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Copper oxide catalysts supported on nanostructured silica SBA‐15 were synthesized with varying copper loadings in a range from 1.1 to 19.4 wt.%. Catalysts were structurally characterized by N2 physisorption, X‐ray diffraction and ex situ as well as in situ diffuse reflectance UV‐Vis spectroscopy. Copper oxide species contained Cu2+ in an octahedral configuration with a tetragonal distortion. Increasing the copper loading resulted in a decreasing optical band gap, which is associated with a growing particle size. Additionally, CuO/SBA‐15 samples were examined by temperature‐programmed reduction confirming a narrow particle size distribution. Structural evolution and catalytic activity were investigated during selective oxidation of propene focusing on product distribution of nucleophilic and electrophilic oxidation. Catalytic testing was carried out using an on‐line GC and MS coupled to a laboratory fixed‐bed reactor. All catalysts selectively oxidized propene to acrolein and propylene oxide (PO). With time on stream activity decreased while selectivity towards acrolein and PO increased. While selectivity towards PO increased with copper loading and, hence, copper oxide particle size, selectivity towards acrolein was largely independent of copper loading.

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“…Die katalytischen Eigenschaften von Molybdänoxiden beleuchtete die Gruppe um Ressler 30. In ihrer Studie der Röntgenabsorptionsspektren untersuchten die Autoren die Rolle der Säure‐Base‐Chemie des Trägeroxids für die MoOx‐Dispersion und die katalytischen Eigenschaften von MoOx/SBA‐15.…”

Section: Molybdän — Spannend Als Oxid Carbid Und Nitridunclassified

Festkörperchemie 2013

2014

Nachr Chem

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Molybdenum oxide supported on nanostructured MgO: Influence of the alkaline support properties on MoOx structure and catalytic behavior in selective oxidation

Cited by 21 publications

References 42 publications

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

Role of Vanadium and Phosphorus in Substituted Keggin‐Type Heteropolyoxo Molybdates Supported on Silica SBA‐15 in Selective Propene Oxidation

Correlation between Copper Oxide Particle Size and Selectivity towards Propylene Oxide in Selective Oxidation of Propene

Festkörperchemie 2013

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