Hydrothermal Synthesis of Urchin-like W-V-O Nanostructures with Excellent Catalytic Performance

Article abstract of DOI:10.1021/acs.inorgchem.8b02513

Urchinlike W-V-O microspheres have been successfully synthesized for the first time by a one-pot hydrothermal approach. The as-synthesized W-V-O material was characterized by several techniques such as XRD, SEM, TEM, FTIR, EDS, BET, and Raman spectroscopy. The characterization results have revealed that the W-V-O microspheres consist of numerous one-dimensional nanobelts radially grown from the center. The typical nanobelts display rectangular cross sections with lengths of several micrometers, widths of about 50 nm, and thicknesses of approximately 10-20 nm. Vanadium oxides are dispersed highly either on the external surface or inside the channel surface of the hexagonal WO₃ structure. In addition, the as-obtained urchin-like W-V-O material was explored as a catalyst for the ammoxidation of 2,4- and 2,6-dichlorotoluene to the corresponding nitriles. The catalytic results have indicated that the W-V-O nanostructures show excellent performance with yields of 2,4- and 2,6-dichlorobenzonitrile respectively reaching up to 77.3 and 75.1%, which are the highest among the previously reported catalysts with two components. The formation process of the urchinlike W-V-O microspheres was simply investigated.

Full text of DOI:10.1021/acs.inorgchem.8b02513

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Hydrothermal Synthesis of Urchin-like W‑V‑O Nanostructures with
Excellent Catalytic Performance
Xiongjian Li,†,‡ Li Sun,† Mingjie Hu,†,‡ Ronghua Huang,§ and Chi Huang*,†,‡
†College of Chemistry and Molecular Sciences, National Demonstration Center for Experimental Chemistry Education (Wuhan
University), Wuhan University, Wuhan, 430072, People’s Republic of China
‡Hubei Military-Civilian Integration and Co-Innovation Center of Aerospace Power and Materials Technology, Wuhan 430072,
People’s Republic of China
§College of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, People’s Republic of China
ABSTRACT: Urchinlike W-V-O microspheres have been successfully synthesized
for the first time by a one-pot hydrothermal approach. The as-synthesized W-V-O
material was characterized by several techniques such as XRD, SEM, TEM, FTIR,
EDS, BET, and Raman spectroscopy. The characterization results have revealed that
the W-V-O microspheres consist of numerous one-dimensional nanobelts radially
grown from the center. The typical nanobelts display rectangular cross sections with
lengths of several micrometers, widths of about 50 nm, and thicknesses of
approximately 10−20 nm. Vanadium oxides are dispersed highly either on the
external surface or inside the channel surface of the hexagonal WO3 structure. In
addition, the as-obtained urchin-like W-V-O material was explored as a catalyst for
the ammoxidation of 2,4- and 2,6-dichlorotoluene to the corresponding nitriles. The
catalytic results have indicated that the W-V-O nanostructures show excellent
performance with yields of 2,4- and 2,6-dichlorobenzonitrile respectively reaching up
to 77.3 and 75.1%, which are the highest among the previously reported catalysts with
two components. The formation process of the urchinlike W-V-O microspheres was simply investigated.
originating from vanadium oxides.14 In this context,
INTRODUCTION
■
tungsten−vanadium binary oxide (W-V-O) catalysts have
Recently, highly ordered superstructures with specific
attracted considerable interest due to the fact that oxides of
morphologies assembled by low-dimensional nanostructures
tungsten are well-known acidic cocatalysts of vanadium-based
have attracted great interest due to their outstanding physical,
catalysts.15 Considering the properties of material closely
chemical, and structural properties.1,2 The high interest lies in
related to the architectures, it is fascinating and significant to
fabricate urchin-like W-V-O composite nanostructures and to
the synthesis of urchin-like nanostructures such as urchin-like
Co3O4 with remarkable electrochemical properties,3 urchin-
like NiCo2O4 with fast photocurrent response,4 urchin-like
further investigate their catalytic properties.
MnWO4 with good magnetic properties,1 and urchin-like WO3
In this paper, we have successfully fabricated urchin-like W-
with excellent gas sensing properties.5
Ammoxidation is an industrially important reaction with
V-O architectures for the first time using V2O5, ammonium
tungstate hydrate and oxalic acid as the starting materials via a
one-pot hydrothermal synthesis method. The catalytic
respect to the product nitriles widely used as organic
behaviors of the prepared urchin-like W-V-O material were
intermediates to prepare great numbers of important
chemicals.6,7 Ammoxidation is partial oxidation with selective
tested in the direct ammoxidation of 2,4- and 2,6-
insertion of nitrogen into a methyl or aldehyde group.8
dichlorotoluene (DCT) to the corresponding dichlorobenzo-
nitrles (DCBNs). DCBNs are valuable intermediates for the
Vanadium oxides as active components have been widely
industrial production of a series of pesticides and many
applied in various oxidation and ammoxidation reactions of
aromatics.9−13 In the reaction course, it is believed that
agricultural chemicals such as chlorfluazuron, flufenoxuron,
and flucycloxuron.16−18 In addition, DCBNs are used to
vanadium undergoes redox cycles where V5+ species with V
O bonds are severely reduced to V4+ via insertion of lattice
prepare a kind of special engineering plastic with high heat-
resistant properties.17 However, it is noted that the catalyzed
oxygen into an oxygen-containing intermediate through a
ammoxidation of DCT to DCBN in high yield is a very difficult
Mars−van Krevelen mechanism, and then such reduced
and challenging process, due to the two bulky chlorine atoms
vanadium species are reoxidized by surface-adsorbed oxygen,
causing difficult accessibility to the methyl group.18 In this
recovering to the original catalyst structure.8 In the past few
decades, a large number of mechanistic studies on the
aforementioned reactions have suggested bifunctional catalysis:
namely, acid sites given by cocatalysts and redox sites
Received: September 4, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
context, the development of effective catalysts for the
ammoxidation of DCT to DCBN is highly desirable. For
comparison, a W-V-O catalyst was also prepared by a solid-
state reaction. In the Results and Discussion, the achieved
performance in terms of yield is compared with those of
previously reported catalysts with two components.
RESULTS AND DISCUSSION
■
The crystal structure and phase composition of the as-obtained
W-V-O composite nanostructures were characterized by using
XRD, as shown in Figure 1. It can be seen that the sample
EXPERIMENTAL SECTION
■
Synthesis of W-V-O Nanostructures. All reagents used in the
experiments were of analytical grade and were used without any
further purification. In a typical procedure, 0.03 mol of commercial
V2O5 powder, 0.005 mol of (NH4)10W12O41, and 0.27 mol of
H2C2O4·2H2O were dispersed into 400 mL of redistilled water with
magnetic stirring. The mixture was heated to 80 °C for about 2 h to
obtain a homogeneous solution. The V/W stoichiometric molar ratio
is 1/1. Then, the above solution was transferred into a 500 mL
stainless steel autoclave, which was sealed and maintained at 260 °C
for 24 h and then cooled to room temperature naturally. The products
were filtered off, washed with distilled water and absolute ethanol
several times to remove any possible residue, and dried in the oven at
70 °C for 12 h. In addition, another of the above mixed solution was
slowly evaporated to dryness on a hot plate with stirring at 80 °C. The
obtained solid was further dried at 110 °C for 8 h in an oven and
calcined in air at 400 °C for 24 h (denoted as SSR-W-V-O).
Characterization. Powder X-ray diffraction (XRD) pattern of the
samples was performed on a D8 X-ray diffractometer equipment with
Cu Kα radiation, λ = 1.54060 Å. The morphology of the products was
observed by scanning electron microscopy (SEM, Quanta 200) and
transmission electron microscopy (TEM, JEM-2100). The chemical
composition of the samples was confirmed by the means of an energy
dispersive X-ray spectrometer (EDS) attached to the scanning
electron microscope (SEM, Quanta 200). The FTIR pattern of the
solid sample was measured using the KBr pellet technique from 4000
to 400 cm−1 with a resolution of 4 cm−1. Raman spectra were carried
out by a Renishaw RM-1000 confocal Raman microspectrometer
equipped with an excitation laser wavelength of 514.5 nm. The
specific surface area was examined by the Brunauer−Emmett−Teller
(BET) N2 gas adsorption method at 77 K and carried out on JW-BK
equipment. Pore size distributions were calculated by the Barrett−
Joyner−Halenda (BJH) formula from the adsorption branch.
Figure 1. XRD patterns of the as-obtained W-V-O composite.
showed a structure related to the hexagonal WO3 (JCPDS: 33-
1387) with the main reflections at 2θ = 13.97, 22.75, 28.19,
36.61, 49.99, and 55.55°.14,19 No peaks of any other phases
were detected. These results suggest that the vanadium oxides
are amorphous and are highly deposited either on the external
surface or inside the channel surface of the hexagonal WO3
structure.20
Figure 2 shows the SEM micrographs of the W-V-O product
with different magnifications. The low-magnification SEM
Catalytic Reaction. Ammoxidation runs were carried out in a 30
mm inside diameter quartz tube fixed-bed reactor. In a typical
experiment, 5 g of catalyst was loaded, and then DCT was introduced
by a micropump, vaporized, and mixed in a preheated vessel with
NH3 and air measured using a gas flow meter. The tests were carried
out under certain conditions (temperature, space velocity (GHSV),
and molar ratio of air or NH3 to DCT). The product stream was
collected every 1/2 h after attaining steady-state conditions and then
analyzed off-line by a gas chromatograph (Lunanruihong, China;
column SE-30) equipped with an FID module. The reaction
equations of the ammoxidation of 2,4-, and 2,6-DCT to give the
corresponding DCBNs are shown in Scheme 1. Note that the samples
after use in ammoxidation reactions qwew cooled to ambient
temperature under a stream of N2.
Figure 2. SEM images of the as-obtained W-V-O composite.
image exhibits a panorama composed of abundant agglom-
erated microspheres with different sizes. The diameter of
microspheres can reach 12 μm or even multiples of 12 μm. It
can be clearly seen from the high-magnification SEM image
that the microspheres consist of numerous one-dimensional
nanobelts radially grown from the center, which appear like
urchins. The TEM image (Figure 3a) shows that the typical
Scheme 1. Ammoxidation of 2,4- and 2,6-DCT to the
Corresponding DCBNs on W-V-O Catalyst
Figure 3. TEM images of the as-obtained W-V-O composite. The
inset gives the SAED pattern.
B
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
nanobelts have rectangular cross sections with lengths of
several micrometers, widths of about 50 nm, and thicknesses of
approximately 10−20 nm. The HRTEM image (Figure 3b)
ascertains that it presents distinctly visual lattice fringes with an
interplanar spacing of 0.315 nm, which matches well with the
[200] crystal planes of hexagonal WO3. The SAED profile (top
right corner in Figure 3a) proves that the W-V-O product is
monocrystalline in structure. The typical EDS spectrum
(Figure 4) corroborates that the nanobelts consist of only O,
in Figure 6. The main band located at around 807 cm−1 with a
small shoulder at 684 cm−1 is related to the two different types
Figure 6. Raman spectrum of the urchin-like W-V-O nanostructures.
of bridging oxygens of O−W−O vibrations in the hexagonal
WO3 structure.23,24 The presence of a band at 988 cm−1
suggests the existence of VO stretches in monomeric and
polymeric V2O5 phases.25,26
The porous structure of the urchin-like W-V-O architecture
was investigated by using the N2 adsorption−desorption
method. As shown in Figure 7, a typical nitrogen isotherm
Figure 4. EDS spectrum of the urchin-like W-V-O nanostructures.
V, and W elements. In addition, the molar ratio of 1.6 for V to
W atoms calculated from the EDS spectrum reveals the
enrichment of vanadium in the surface region. These above
results indicate the existence of amorphous VOx species which
are deposited either on the external surface or inside the
channel surface of the hexagonal WO3 structure, in good
accord with the XRD results.
Figure 5 shows the FTIR spectrum of the as-obtained W-V-
O composite nanostructures as well as that of V2O5. The FTIR
Figure 7. N2 adsorption and desorption isotherms and pore size
distribution curve (inset) of the urchin-like W-V-O nanostructures.
with type-H3 desorption hysteresis loop is observed, indicating
the mesoporous structure of the material. The pore size
distribution calculated using the Barrett−Joyner−Halenda
(BJH) method shows a peak centered at around 3.6 nm
(inset in Figure 7), while the average pore diameter is
approximately 12.88 nm. The BET surface area of the material
is 5.2 m2 g−1.
To investigate the formation process of the urchin-like W-V-
O microspheres, a series of time-dependent experiments were
carried out. Figure 8 shows the corresponding SEM images of
the samples produced at different time periods. At the early
stage (3 h), the sample was composed of solid spheres with
fairly large variability in particle sizes (Figure 8a). When the
reaction time was extended to 6 h, it can be clearly seen that
numerous small nanobulks with a very high density grew on
the surface of the spheres (Figure 8b). When the reaction time
was prolonged further to 12 h, inhomogeneous urchin-like
microspheres assembled by nanobelts became the predominant
microspheres (Figure 8c). After the reaction was prolonged to
24 h, urchin-like microspheres were formed (Figure 2). On the
basis of the above experimental results, two steps, i.e.,
nucleation and subsequent growth, were proposed to explain
Figure 5. FTIR spectra of (a) the urchin-like W-V-O nanostructures
and (b) V2O5.
spectrum of V2O5 was examined for the purpose of
comparison. The absorption band at 1625 cm−1 is the
characteristic bending vibration of absorbed molecular water,
while the band at 1401 cm−1 is assigned to C−H stretching
caused by residual impurities.21 The appearances of bands at
about 1016, 825, and 577 cm−1, assigned to the stretching
vibrations of VO and asymmetric and symmetric stretching
vibrations of V−O−V, indicate the presence of the V2O5
phase.22
Raman spectroscopy was employed to provide further
evidence of the structure of the W-V-O composite, as shown
C
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Figure 8. SEM images of the products prepared at 260 °C for different reaction times: (a) 3 h; (b) 6 h; (c) 12 h.
the growth of urchin-like W-V-O nanostructures. The whole
process can be expressed as depicted in Figure 9. In terms of
Table 1. Ammoxidation of 2,4-DCT on the W-V-O
Catalysts
a
catalyst
urchins
SSR-W-V-O
conversion (%)
yield (%)
selectivity (%)
90.0
85.7
77.3
67.6
85.9
78.9
a
Conditions: 2,4-DCT:air:NH3 molar ratio 1:25:9; T = 390 °C;
GHSV = 369 h−1.
Figure 9. Schematic illustrations of the possible formation processes
of the urchin-like W-V-O nanostructures.
obviously observed from Table 2 that the yields of 2,4- and 2,6-
DCBN obtained on urchin-like W-V-O in our work are the
highest among the previously reported catalysts with two
components. For the supported catalysts in the literature,
VPO/Al2O3 exhibited a higher yield of 2,6-DCBN in
comparison to the VPO/SiO2 catalysts due to Al2O3 showing
better acidic properties than SiO2. For unsupported V-Cr-O,
VPO, and (NH4)2[(VO)3(P2O7)2] catalysts, the similar
observation can be found that the order of catalytic behavior
of these catalysts was consistent with the acidic order of the
cocatalysts. These results have indicated that the catalytic
performance of vanadium-based catalysts greatly depends on
the acidic properties of the cocatalyst. Mechanistic studies of
ammoxidation on vanadium-based oxides have suggested that
VOx species as redox sites catalyze partial oxidation of
alkylaromatics to aldehyde intermediates; meanwhile, the
acid sites in close proximity to the redox sites (VOx) adsorb
NH3 and insert the nitrogen species into the intermediate.27
The two processes are respectively responsible for the active
and selective properties of catalysts in ammoxidation. For the
prepared urchin-like W-V-O catalyst, WO3 shows medium to
strong acid strength containing the Brønsted and/or Lewis
acid14 in favor of the formation of acid sites, leading to
improvement in the efficiency of nitrogen insertion.15 In
addition, WO3 also acts as a support to facilitate the dispersion
of vanadium oxides, increasing the number of redox sites. The
enrichment of dispersed amorphous VOx species in the surface
the first step, initial WO3 nuclei were formed. Then the
secondary nucleation of oxides of tungsten and vanadium
occurred preferentially at the surface defect sites of the initial
WO3 nuclei and grew along the [200] direction.5 Such a
mechanism seems to be a common phenomenon during the
crystal growth process and is observed for several material
systems, such as carbonates, silicates, tungstates, and so on.4
The catalytic results obtained in the ammoxidation of 2,6-
DCT on W-V-O catalysts are shown in Figure 10. It can be
seen that the urchin-like W-V-O catalyst displays much better
catalytic performance in comparison to SSR-W-V-O catalyst
under identical conditions. The best yield of 2,6-DCBN
obtained on urchins reached up to 75.1% with a conversion of
88.2%, while the SSR-W-V-O sample exhibited a maximum
2,6-DCBN yield of 63.1% at a conversion of 83.2%. In
addition, the ammoxidation of 2,4-DCT was also investigated.
Table 1 shows the results obtained on W-V-O catalysts under
optimum conditions. The maximum 2,4-DCBN yield achieved
on the urchin-like W-V-O catalyst was up to 77.3% which was
much higher than that of the sample prepared by the solid-
state reaction (ca. 67.6%), indicating a prominent improve-
ment in the catalytic performance.
Table 2 summarizes the results of the ammoxidation of 2,4-
and 2,6-DCT in the literature and in this work. It can be
Figure 10. Conversion (a) and yield (b) behavior of W-V-O catalysts in the ammoxidation of 2,6-DCT (2,6-DCT:air:NH3 molar ratio 1:20:9,
GHSV = 315 h−1.
D
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
Table 2. Comparison of the Results of the Ammoxidation of 2,4- and 2,6-DCT in the Literature
substrate
catalyst
VPO/SiO2
(NH4)2[(VO)3(P2O7)2]
VPO/Al2O3
bulk VPO
VPO/SiO2
VPO/SiO2
V-Cr-O
conversion (%)
yield (%)
selectivity (%)
ref
2,4-DCT
2,6-DCT
2,6-DCT
2,6-DCT
2,6-DCT
2,6-DCT
2,6-DCT
2,4-DCT
2,6-DCT
97
50
99
92
87
90
78
90
88
70
18
71
55
57
57
70
77
75
72
36
72
60
66
63
90
86
85
29
30
31
33
32
33
34
urchins
urchins
this work
this work
(5) Li, T.; Zeng, W.; Miao, B.; Zhao, S.; Li, Y.; Zhang, H. Urchinlike
hex-WO3 Microspheres: Hydrothermal Synthesis and Gas-Sensing
Properties. Mater. Lett. 2015, 144, 106−109.
region of the urchin-like W-V-O catalyst contributes to
enhancing the partial oxidation of DCT to a dichlorobenzal-
dehyde intermediate.28 As a consequence, the prepared urchin-
like W-V-O catalyst exhibits excellent catalytic properties.
(6) Dhachapally, N.; Kalevaru, V. N.; Bruckner, A.; Martin, A. Metal
̈
Vanadate Catalysts for the Ammoxidation of 2-Methylpyrazine to 2-
Cyanopyrazine. Appl. Catal., A 2012, 443-444, 111−118.
(7) Dropka, N.; Smejkal, Q.; Kalevaru, V. N.; Martin, A. Laboratory
Set-up to Pilot Plant Investigations on Vapour Phase Ammoxidation
of 2, 6-Dichlorotoluene. Appl. Catal., A 2008, 349, 125−132.
(8) Martin, A.; Kalevaru, V. N.; Smejkal, Q. Ammoxidation of 2,6-
Dichlorotoluene-From First Trials to Pilot Plant Studies. Catal. Today
2010, 157, 275−279.
CONCLUSION
■
In conclusion, nanobelt-built urchin-like W-V-O composite
microspheres have been successfully prepared by a one-pot
hydrothermal method using V2O5, ammonium tungstate
hydrate, and oxalic acid as the starting materials. The as-
prepared material consists of numerous one-dimensional
nanobelts radially grown from the center with lengths of
several micrometers, widths of about 50 nm, and thicknesses of
approximately 10−20 nm. Vanadium oxides are dispersed
highly either on the external surface or inside the channel
surface of the hexagonal WO3 structure. In the ammoxidation
reactions of 2,4- and 2,6-dichlorotoluene, the W-V-O material
shows excellent performance with yields of 2,4- and 2,6-
dichlorobenzonitrile respectively reaching up to 77.3 and
75.1% due to the novel nanostructures.
(9) Dhachapally, N.; Kalevaru, V. N.; Radnik, J.; Martin, A. Tuning
the Surface Composition of Novel Metal Vanadates and its Effect on
the Catalytic Performance. Chem. Commun. 2011, 47, 8394−8396.
(10) Martin, A.; Lucke, B. Ammoxidation and Oxidation of
̈
Substituted Methyl Aromatics on Vanadium-Containing Catalysts.
Catal. Today 2000, 57, 61−70.
(11) Lucke, B.; Narayana, K. V.; Martin, A.; Jahnisch, K. Oxidation
̈
̈
and Ammoxidation of Aromatics. Adv. Synth. Catal. 2004, 346, 1407−
1424.
(12) Martin, A.; Kalevaru, V. N. Heterogeneously Catalyzed
Ammoxidation: A Valuable Tool for One-Step Synthesis of Nitriles.
ChemCatChem 2010, 2, 1504−1522.
AUTHOR INFORMATION
Corresponding Author
*E-mail for C.H.: chihuang@whu.edu.cn.
ORCID
Xiongjian Li: 0000-0003-0702-8738
Ronghua Huang: 0000-0002-0423-2904
Notes
■
(13) Dwivedi, R.; Sharma, P.; Sisodiya, A.; Batra, M. S.; Prasad, R. A
DFT-Assisted Mechanism for Evolution of the Ammoxidation of 2-
Chlorotoluene (2-CLT) to 2-Chlorobenzonitrile (2-CLBN) over
Alumina-Supported V2O5 Catalyst Prepared by a Solution Combus-
tion Method. J. Catal. 2017, 345, 245−257.
́
(14) Soriano, M. D.; Concepcion, P.; Nieto, J. M. L.; Cavani, F.;
Guidetti, S.; Trevisanut, C. Tungsten-Vanadium Mixed Oxides for the
Oxidehydration of Glycerol into Acrylic Acid. Green Chem. 2011, 13,
2954−2962.
The authors declare no competing financial interest.
(15) Goto, Y.; Shimizu, K.; Murayama, T.; Ueda, W. Hydrothermal
Synthesis of Microporous W-V-O as an Efficient Catalyst for
Ammoxidation of 3-Picoline. Appl. Catal., A 2016, 509, 118−122.
ACKNOWLEDGMENTS
This work was partially supported by the National Natural
Science Foundation of China (Grant 51572201).
■
(16) Kalevaru, V. N.; Lucke, B.; Martin, A. Synthesis of 2, 6-
̈
Dichlorobenzonitrile from 2, 6-Dichlorotoluene by Gas Phase
Ammoxidation over VPO Catalysts. Catal. Today 2009, 142, 158−
164.
REFERENCES
■
(1) Zhou, Y. X.; Zhang, Q.; Gong, J. Y.; Yu, S. H. Surfactant-assisted
Hydrothermal Hynthesis and Magnetic Properties of Urchin-like
MnWO4 Microspheres. J. Phys. Chem. C 2008, 112, 13383−13389.
(2) Boschloo, G. K.; Goossens, A.; Schoonman, J. Photo-
electrochemical Study of Thin anatase TiO2 Films Prepared by
Metallorganic Chemical Vapor Deposition. J. Electrochem. Soc. 1997,
144, 1311−1317.
(3) Xiao, Y.; Liu, S.; Li, F.; Zhang, A.; Zhao, J.; Fang, S.; Jia, D. 3D
Hierarchical Co3O4 Twin-Spheres with an Urchin-Like Structure:
Large-Scale Synthesis, Multistep-Splitting Growth, and Electro-
chemical Pseudocapacitors. Adv. Funct. Mater. 2012, 22, 4052−4059.
(4) Wang, Q.; Liu, B.; Wang, X.; Ran, S.; Wang, L.; Chen, D.; Shen,
G. Morphology Evolution of Urchin-like NiCo2O4 Nanostructures
and Their Applications as Psuedocapacitors and Photoelectrochem-
ical cells. J. Mater. Chem. 2012, 22, 21647−21653.
(17) Suzuki, H.; Kimura, Y. Synthesis of 3, 4-Difluorobenzonitrile
and Monofluorobenzonitriles by Means of Halogen-Exchange
Fluorination. J. Fluorine Chem. 1991, 52, 341−351.
(18) Dropka, N.; Kalevaru, V. N.; Martin, A.; Linke, D.; Lucke, B.
̈
The Kinetics of Vapour-Phase Ammoxidation of 2, 6-Dichlorotoluene
over VPO Catalyst. J. Catal. 2006, 240, 8−17.
(19) Szilagyi, I. M.; Madarasz, J.; Pokol, G.; Hange, F.; Szalontai, G.;
Varga-Josepovits, K.; Toth, A. L. The Effect of K+ Ion Exchange on
the Structure and Thermal Reduction of Hexagonal Ammonium
Tungsten Bronze. J. Therm. Anal. Calorim. 2009, 97, 11−18.
́
(20) Chieregato, A.; Bandinelli, C.; Concepcion, P.; Soriano, M. D.;
Puzzo, F.; Basile, F.; Cavani, F.; Nieto, J. M. L. Structure-Reactivity
Correlations in Vanadium-Containing Catalysts for One-Pot Glycerol
Oxidehydration to Acrylic Acid. ChemSusChem 2017, 10, 234−244.
E
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(21) Zhang, Y.; Zhang, J.; Zhong, Y.; Yu, L.; Deng, Y.; Huang, C.;
Liu, X. Direct Fabrication of Organic Carbon Coated VO2(B)
(VO2(B) @ C) Core-Shell Structured Nanobelts by One Step
Hydrothermal Route and its Formation Mechanism. Appl. Surf. Sci.
2012, 263, 124−131.
(22) Bulushev, D. A.; Kiwi-Minsker, L.; Rainone, F.; Renken, A.
Characterization of Surface Vanadia Forms on V/Ti-Oxide Catalyst
via Temperature-Programmed Reduction in Hydrogen and Spectro-
scopic Methods. J. Catal. 2002, 205, 115−122.
(23) Zheng, Z.; Yan, B.; Zhang, J.; You, Y.; Lim, C. T.; Shen, Z.; Yu,
T. Potassium Tungsten Bronze Nanowires: Polarized Micro-Raman
Scattering of Individual Nanowires and Electron Field Emission from
Nanowire Films. Adv. Mater. 2008, 20, 352−356.
(24) Songara, S.; Kupta, V.; Patra, M. K.; Singh, J.; Saini, L.; Gowd,
G. S.; Vadra, S. R.; Kumar, N. Tuning of Crystal Phase Structure in
Hydrated WO3 Nanoparticles Under Wet Chemical Conditions and
Studies on their Photochromic Properties. J. Phys. Chem. Solids 2012,
73, 851−857.
(25) Olthof, B.; Khodakov, A.; Bell, A. T.; Iglesia, E. Effects of
Support Composition and Pretreatment Conditions on the Structure
of Vanadia Dispersed on SiO2, Al2O3, TiO2, ZrO2, and HfO2. J. Phys.
Chem. B 2000, 104, 1516−1528.
(26) Argyle, M. D.; Chen, K.; Bell, A. T.; Iglesia, E. Effect of Satalyst
Structure on Oxidative Dehydrogenation of Ethane and Propane on
Alumina-Supported Vanadia. J. Catal. 2002, 208, 139−149.
(27) Goto, Y.; Shimizu, K.; Kon, K.; Toyao, T.; Murayama, T.;
Ueda, W. Efficient Ammoxidation of Toluene by Hydrothermally
Synthesized Layered Tungsten-Vanadium Complex Metal Oxides. J.
Catal. 2016, 344, 346−353.
(28) Radnik, J.; Dhachapally, N.; Kalevaru, V. N.; Sinev, I.; Grunert,
̈
W.; Martin, A. Impact of the Outermost Layer of Various Solid Metal
Vanadate Catalysts on Ammoxidation of 2-Methylpyrazine to 2-
Cyanopyrazine. Catal. Commun. 2015, 71, 97−101.
(29) Huang, C.; Zheng, Q.; Zu, C.; Xie, G.; Chen, Y. Ammoxidation
of 2,4-Dichlorotoluene on VPO/SiO2 Catalyst. China J. Mol. Catal.
1999, 13, 467−470.
(30) Martin, A.; Lucke, B.; Wolf, G. U.; Meisel, M. Effect of the
̈
Position of Cl-Substituents on the Nitrile Formation During the
Ammoxidation of Chlorotoluenes. Catal. Lett. 1995, 33, 349−355.
(31) Kalevaru, V. N.; Lucke, B.; Martin, A. Synthesis of 2, 6-
̈
Dichlorobenzonitrile from 2, 6-Dichlorotoluene by Gas Phase
Ammoxidation over VPO Catalysts. Catal. Today 2009, 142, 158−
164.
(32) Xie, G.; Hang, C. Ammoxidation of Methylaromatics over
VPO/SiO2 Catalysts. Indian J. Chem. Technol. 2007, 14, 371−375.
(33) Huang, C.; Zheng, Q.; Xie, G.; Xu, C.; Han, Q.; Chen, Y.
Ammoxidation of 2,6-Dichlorotoluene on Silica Supported Vana-
dium-Phosphorus Oxide Catalyst. China. J. Catal. 1999, 20, 679−680.
(34) Xu, L.; Zhang, Y.; Deng, Y.; Zhong, Y.; Mo, S.; Cheng, G.;
Huang, C. One-step Hydrothermal Synthesis and Characterization of
V-Cr-O Nanospheres and their Excellent Performance in the
Ammoxidation of 3,4- and 2,6-DCT. Mater. Res. Bull. 2013, 48,
3620−3624.
F
DOI: 10.1021/acs.inorgchem.8b02513
Inorg. Chem. XXXX, XXX, XXX−XXX