Ternary Phases with the Mo5O14 Type of Structure. II. A Study of the Molybdenum-Niobium-Oxygen and Molybdenum-Tantalum-Oxygen Systems.

Ekström, Thommy; Nygren, Mats; Simov, D.; Øye, H. A.; Svensson, Sigfrid

doi:10.3891/acta.chem.scand.26-1836

Cited by 34 publications

(19 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We note already in the synthesis of the Ta M1 phase that it is more easily formed than the Nb equivalent and that less Ta is required in solution to form the M1 phase. This is also consistent with the early synthetic and structural work of Ekstro¨m et al [23,24] using Group V elements as structure directing moieties in the synthesis of complex molybdenum oxides. He found that complex open structures of molybdenum oxides were stabilized with Group V elements in the order Ta > Nb > V. While the stability of the crystalline materials is governed by thermodynamics, the synthesis process is governed by kinetics of the nanoparticles as they form and assemble in solution [25].…”

Section: The Active Centers Of M1 and M2 Of Movtateo Catalystssupporting

confidence: 89%

Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts

Grasselli

Buttrey

Burrington³

et al. 2006

Top Catal

108

View full text Add to dashboard Cite

Selective as well as waste forming active centers were defined for MoVNbTeO and MoVTaTeO catalysts in the ammoxidation of propane to acrylonitrile and all catalytic functionalities were assigned to specific elements at the respective active centers. Symbiosis between M1 and M2 phases of these catalysts was observed, with phase cooperation being more extensive in the Nb than Ta containing compositions. The difference in catalytic effectiveness arises most likely because contact and surface area exposure of the two respective, cooperating phase pairs are not equal. The M1 phase of the catalysts is reducible by propane and ammonia in the absence of dioxygen and is regenerable to its original, fully oxidized state by dioxygen (air). No structural collapse is observed even after 120 C 3 H 8 + NH 3 reduction pulses. The so induced reduction of the catalyst extends up to 70 layers deep. The product distribution over the first few pulses is very similar to that under catalytic conditions, supporting the concept that lattice oxygen is involved in the catalytic ammoxidation process. Therefore, the ammoxidation of paraffins is a redox process, as is of course the well-known olefin ammoxidation process.

show abstract

Section: The Active Centers Of M1 and M2 Of Movtateo Catalystssupporting

confidence: 89%

Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts

Grasselli

Buttrey

Burrington³

et al. 2006

Top Catal

108

View full text Add to dashboard Cite

show abstract

“…6b). Mo 5 O 14 tolerates the incorporation of considerable amounts of different 5 and 6 transition metals like vanadium, tungsten, niobium, and/or tantalum [29][30][31][32]. It is well known that the incorporation of these el- ements leads to stabilization of the structure.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Selective oxidative dehydrogenation of ethane on MoVTeNbO mixed metal oxide catalysts

Botella

2004

Journal of Catalysis

236

View full text Add to dashboard Cite

“…This oxide forms at a definite transition metal ratio of Mo : V : W equal to 0.68:0.23:0.09. At the same time binary molybdenum based oxides doped with different elements such as Nb, W and Ta have been synthesised and their structure was identified as that of the Mo 5 O 14 -type [11,12]. These phases were found to be stable at a wide temperature range and a broad variation of the element ratios.…”

Section: Introductionmentioning

confidence: 99%

The synthesis and structure of a single-phase, nanocrystalline MoVW mixed-oxide catalyst of the Mo5O14 type

Knobl

Зенковец

Kryukova

et al. 2003

Journal of Catalysis

View full text Add to dashboard Cite

The different preparation steps are characterized to the single phase, crystalline, ternary oxide (MoVW) 5O14, which is important for catalytic, mild selective oxidation reactions. For the synthesis of this oxide, solutions of ammonium heptamolybdate, ammonium metatungstate, and v anadyl oxalate were spray-dried followed by different thermal treatments. The structures of the materials formed at each preparation step, starting from the precursor to the final product, were studied using scanning and transmission electron microscopy, X -ray powder diffraction, thermal analysis, and Raman spectroscopy. Raman spectroscopy was also applied to shed some light into the aqueous chemistry of the mixed precursor solutions. Raman data indicates that a molecular structure is already formed in solution which seems to be closely related to that of the final crystalline Mo5O14-type oxide. X-ray diffraction revealed that the thermal treatment steps strongly affect the degree of crystallinity of the ternary Mo5O14 oxide. Transmission electron microscopy with energy dispersive microanalysis confirmed the presence of V and W in the molybdenum oxide particles and gave evidence for the (010) plane as the most developed face of the crystals of this phase. Details of the structural transformation of this system at the different preparation and calcination steps are discussed in relation to their performance in the selective partial oxid ation of acrolein to acrylic acid.

show abstract

Ternary Phases with the Mo5O14 Type of Structure. II. A Study of the Molybdenum-Niobium-Oxygen and Molybdenum-Tantalum-Oxygen Systems.

Cited by 34 publications

References 0 publications

Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts

Active centers, catalytic behavior, symbiosis and redox properties of MoV(Nb,Ta)TeO ammoxidation catalysts

Selective oxidative dehydrogenation of ethane on MoVTeNbO mixed metal oxide catalysts

The synthesis and structure of a single-phase, nanocrystalline MoVW mixed-oxide catalyst of the Mo5O14 type

Contact Info

Product

Resources

About