Mixed molybdenum oxide based partial oxidation catalyst

The structural genesis of a complex (MoVW)5O14 oxide during thermal treatments and its redox behavior at elevated temperatures

“…Considering the Mo-O distances determined by XRD, the channel di- At the same time, NMR spectroscopy deliveres certain hints on the presence of V 5+ ions in an uncommon, maybe highly distorted trigonal pyramidal coordination. We may speculate that these ions substitute Mo 5+ ions in pentagonal bipyramidal sites [9]. On the other hand, Millet [33] in this case, we cannot exclude an occupation of the channels.…”

“…An assignment of chemical and structural specifics to catalytic properties is based upon sterical interpretation rather than on experimental results of physical and chemical characterization [7]. Recently, Mo-V-W mixed oxides consisting of (MoVW) 5 O 14 as the major phase have been studied in the selective oxidation of various substrates including methanol, propylene and acrolein [8][9][10]. In contrast to wellcrystallized Mo 5 O 14 oxide, which shows poor activity in the oxidation of acrolein, an amorphous material equally composed but pretreated under different conditions exhibits much increased activity.…”

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts

“…Therefore, we shall assume that, as confirmed by LRS, θ- One of the main questions to answer is the formation of solid solutions in the metastable θ-phase, which is known to be stabilized by several cations to a given extent [45]. The maximum solubility is, e.g., 11 at.% of V, 9 at.% of Nb and up to 30 at.% of W. In Nb-free catalysts, θ may be stabilized as (V 0.07 Mo 0.93 ) 5 [34]. Generally speaking, the thermodynamic trend exhibited by particles of amorphous materials is to reorganize and to grow in order to reach a more stable state, unless they are stabilized in another manner.…”

“…Multicomponent catalysts have flourished recently because of the versatility of the MoV system which accommodates several types of dopant, such as catalysts for mild oxidation of propane to acrylic acid [27][28][29][30][31][32]. If tungsten is generally preferred to Nb for these reactions, the Mo 5 O 14 -type oxide is often present in the system as detected by XRD and Raman spectroscopy [20,[30][31][32][33][34], and as such it may be a key factor to relate to catalytic properties. However, the structure of other phases present in the MoVXYO system and which are related with the presence of dopants X, Y, has been recently solved [35][36][37][38][39][40][41][42] and their presence could make the difference with the MoVNbO system more active for ethane oxidation.…”

Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides

“…Mo 5 O 14 and MoO 3 seem to be stable against the reduction process. This can be explained by the stabilisation of thermodynamically metastable phases by tungsten 9 46 The re-oxidation of the reduced crystalline samples of both hydrochemical preparation methods in air again results in XRD patterns with crystalline structures. But a reconstruction of the hexagonal (V,Mo)O 3 structure type found before reduction fails.…”