C O M M U N I C A T I O N S
Table 1. Catalytic Performance of MoVNbTe(Sb)Ox for
notched edge was produced during the calcination. Similar types
of crystallites were also observed for all the active and selective
catalysts with the characteristic XRD patterns. We consider that
the superior catalytic performance (including the activation of
alkanes) originates from the crystallites with the specific disposition
of constituents in addition to the layered structure and that niobium
plays an important role in the formation of the crystalline phase.
The structural identification of the crystalline phase for MoVNbTe-
(Sb)Ox will be reported elsewhere, and the manner of POM linkage
relevant to the structure is now under investigation.
The present results provide a new synthesis route to molybde-
num- and vanadium-based composite oxide catalysts and also
suggest that the self-organization of POMs with the reduction pre-
cisely controlled under mild conditions is a potential tool to diversify
a new class of oxides including metastable or low-temperature oxide
phases. We believe that the exploration and comprehension of the
block-construction manner using linkable POMs will lead to the
generation of innovative inorganic materials pre-designed with
interesting physical, chemical, and structural properties.
(Amm)Oxidation of Propanea
yieldd of
amount of
calcin- reaction conversiond acrylonitrile
c
catalyst
reducing agents ation
temp
of
or acrylic
compositionb
(mol/mol-Mo) temp (°C) (°C) propane (%) acid (%)
ammoxidatione
Mo1V0.30Nb0.12Te0.17Ox
Mo1V0.30Nb0.12Te0.17Ox
Mo1V0.30Nb0.12Te0.17Ox
Mo1V0.30Nb0.12Te0.17Ox
Mo1V0.30Nb0.12Te0.16Ox
Mo1V0.25Nb0.20Te0.17Ox
Mo1V0.30Nb0.07Sb0.17Ox
Mo1V0.30Nb0.07Sb0.17Ox
0.000
600
600
600
600
600
600
625
625
427
428
427
426
429
424
434
435
11.4
86.9
81.8
77.7
85.7
67.6
81.8
61.2
4.6
51.6
48.1
45.2
53.5
41.1
46.4
30.0
0.134g
0.134h
0.268i
0.136j
0.131g
0.068g
0.068h
oxidationf
Mo1V0.25Nb0.20Te0.17Ox
Mo1V0.30Nb0.07Sb0.17Ox
0.096j
0.051g
600
625
432
427
69.2
62.4
46.3
34.2
a Determined by on-line GC using an internal standard. b Determined by
energy dispersive XRF. c For 2 h in a stream of N2. d Based on feed propane.
e Catalyst (550 mg), feed gas (500 N mL/h), mol ratio (C3H8/NH3/air ) 1/1.2/
15). f Catalyst (550 mg), feed gas (880 N mL/h), mol ratio (C3H8/O2/N2/H2O )
1/3/7/19). g Hydrazine sulfate. h Hydrazine hydrate. i Hydroxylamine sulfate.
j Acetol (hydroxyacetone).
Supporting Information Available: Experimental procedures
including typical preparation of the catalyst and Figure showing
variation in catalytic performance with amount of reducing agent (PDF).
This material is available free of charge via the Internet at http://
pubs.acs.org.
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Figure 1. X-ray diffraction patterns of solid samples for Mo1V0.25Nb0.20
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Te0.17Ox composite prepared using hydrazine sulfate (0.131 mol/mol-Mo): (a)
dried gel prior to calcination, (b) after calcination at 600 °C 2 h in a stream
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Figure 2. SEM image of Mo1V0.25Nb0.20Te0.17Ox composite oxide prepared
by using hydrazine sulfate (0.131 mol/mol-Mo) and calcined at 600 °C for 2
h in a stream of N2.
catalyst structure for the selective oxidation not only of al-
kanes7,10-12 but also other oxygenates.13 Ueda et al. speculated that
the phase with a layered structure resulted from a directed stacking
of slabs due to the self-organization of Anderson-type heteropoly-
molybdate units.10a However, the formation of the layer at the 4.0
Å d-spacing was not explained by assembly of the Anderson-type
units consisting of only edge-sharing octahedra. The process should
contain the covalent linkages of POMs through corner-sharing
octahedra and the rearrangement accompanying them.
Although the Mo5O14 structure in which the corner and edge-
sharing MoO6 octahedra are involved, typically exhibits this layered
pattern at 4.0 Å d-spacing in XRD,5b,13 the dominant diffraction
peaks for the catalytically active MoVNbTe(Sb)Ox were not iden-
tified with the Mo5O14 structure as demonstrated in Figure 1.
Moreover, as can be seen in the SEM image (Figure 2), the
formation of the well-crystallized rod-shape crystallites with a
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