A Versatile VMPO Catalyst Prepared In Situ for Oxidative Ammonolysis of Isomeric Picolines and Xylenes

Article abstract of DOI:10.1134/S1070363220020218

Abstract: The V₂O₅–MoO₃–P₂O₅ (VMPO) catalyst has been prepared in situ by thermal decomposition of vanado-molybdophosphoric acid (PMoV) on TiO₂ support at 475°C. The TiO₂ supported VMPO catalysts are characterized by FT–IR, XRD, BET surface area, NH₃–TPD, and H₂–TPR. Morphology of the catalyst has been studied by TEM. The accumulated data indicate decomposition of PMoV and presence of phosphate and pyrophosphate phases of molybdenum and vanadium after calcination. TPD and TPR studies exhibit the moderate acidity and presence of V⁴⁺ in the material, respectively. The VMPO catalyst has been used for ammoxidation of six different compounds including three isomeric picolines and three isomeric xylenes to the corresponding nitriles with the yield of 90–96%.

Full text of DOI:10.1134/S1070363220020218

ISSN 1070-3632, Russian Journal of General Chemistry, 2020, Vol. 90, No. 2, pp. 292–298. © Pleiades Publishing, Ltd., 2020.
A Versatile VMPO Catalyst Prepared In Situ
for Oxidative Ammonolysis of Isomeric Picolines and Xylenes
a
b
a,
Rabinarayan Senapati , D. D. Pathak , and P. Dutta *
a
CSIR-Central Institute of Mining and Fuel Research, P.O. FRI, Dhanbad, 828108 India
b
Department of Applied Chemistry, IIT-ISM, Dhanbad, 826004 India
*
e-mail: pdutta2002in@yahoo.co.in
Received February 8, 2019; revised January 27, 2020; accepted February 5, 2020
Abstract—The V O –MoO –P O (VMPO) catalyst has been prepared in situ by thermal decomposition of vanado-
2
5
3
2
5
molybdophosphoric acid (PMoV) on TiO support at 475°C. The TiO supported VMPO catalysts are characterized
2
2
by FT–IR, XRD, BET surface area, NH –TPD, and H –TPR. Morphology of the catalyst has been studied by TEM.
3
2
The accumulated data indicate decomposition of PMoV and presence of phosphate and pyrophosphate phases of
molybdenum and vanadium after calcination. TPD and TPR studies exhibit the moderate acidity and presence of
4
+
V in the material, respectively. The VMPO catalyst has been used for ammoxidation of six different compounds
including three isomeric picolines and three isomeric xylenes to the corresponding nitriles with the yield of 90–96%.
Keywords: picoline, xylene, VMPO, oxidative ammonolysis, nitrile
DOI: 10.1134/S1070363220020218
INTRODUCTION
In the present study, TiO supported VMPO catalyst
2
was prepared from a precursor vanado-molybdophos-
phoric acid by a relatively uncomplicated method. The
VMPO catalyst was used for ammoxidation of six dif-
ferent compounds including three isomeric picolines
and three isomeric xylenes to corresponding nitriles.
The catalytic systems of the type were characterized by
different techniques in order to correlate their catalytic
activity.
Vapour phase ammoxidation is one of the prospec-
tive routes for production of a number of important
chemicals used in industry [1, 2]. The major advantage
of that method over conventional ones is combining
several stages into a single process of catalytic vapour
phase ammoxidation. Also the reagents involved are in-
expensive air/O and NH , and the reaction is carried
2
3
out under the atmospheric pressure.
RESULTS AND DISCUSSION
Earlier ammoxidation of 3-picoline to 3-cyanopyri-
dine was carried out under catalysis by VZrAlON [3].
Some other catalytic systems were also used for promot-
ing ammoxidation of various organic compounds [4–7].
The catalysts containing V O in combination with MoO
N adsorption–desorption. The Brunauer–Emmett-
2
Teller (BET) surface area was measured by N adsorp-
2
tion on the surface of catalysts VMPO-10, VMPO-20,
VMPO-30, VMPO-40, and TiO support (Table 1). The
2
2
5
3
and P O were particularly efficient in ammoxidation
2
5
Table 1. BET surface area and acidity of catalysts
reactions [7]. The catalytic properties of V O depended
2
5
on the methods of its preparation. According to Ray
et al. [7], V O prepared from vanadyl oxalate was more
2
Catalyst
TiO2
Surface area, m /g Acidity, μmol/g
2
5
73
69
62
59
48
63.06
68.74
71.80
67.50
64.30
efficient than that prepared from ammonium metavana-
date. In our earlier research the effect of high content of
MoO in V O –MoO –P O (VMPO) catalyst had been
VMPO-10
VMPO-20
VMPO-30
VMPO-40
3
2
5
3
2
5
studied [8]. VMPO prepared from vanadyl oxalate, am-
monium heptamolybdate and orthophosphoric acid gave
96% yield of pyridine 3-carbonitrile upon ammoxidation
of 3-picoline.
2
92

A VERSATILE VMPO CATALYST PREPARED IN SITU
293
5
4
1
364
1
212
989
89
220
3
2
1
744
9
1
742
1367 1220
1356
989
5
81
1
723
1
(
P–O–P)
(O–H)
1
709
1
1
593
1055
674
(O–H)
(P–Oa)
(P–O–P)
1370
1217
1
736
9
44
(V=O)
2
000
1600
1200
800
400
2
000
1600
1200
Ȟ, cm–1
800
400
Ȟ, cm–1
Fig. 2. FT-IR spectra of (1) VMPO-10, (2) VMPO-20,
(3) VMPO-30, (4) VMPO-40, and (5) TiO2.
Fig. 1. FT-IR spectrum of PMoV.
2
surface area of TiO was 73 m /g and it decreased from
6
alyst. So, activity of the material increased appreciably
due to the presence of vanadium and molybdenum pyro-
phosphate and phosphate, respectively. Probably slight
shifting occurred in each spectrum due to enhancement
2
2
9 to 48 m /g with increase in VMPO loading from
VMPO-10 to VMPO-40 which could be attributed to
blocking of pores on the surface of TiO by VMPO mol-
2
ecules [9].
of different wt % of VMPO loading on TiO (the anatase
2
form).
FT-IR. The main characteristics bands of PMoV
(
1
Fig. 1) [10–12] were observed in the region of 500–
550 cm . FT-IR spectra of calcined VMPO-10,
TGA analysis. The TGA profiles (Fig. 4) demon-
strated weight loss in the range of room temperature to
450°C indicating two distinct stages. In the first stage
between room temperature and 155°C loss of adsorbed
water (i.e. <5%) took place. The second stage at above
155°C indicated the weight loss of water of crystallisa-
tion that bound the Keggin unit closely in the secondary
–1
VMPO-20,VMPO-30, andVMPO-40 catalysts andTiO2
Fig. 2) exhibited a shift and broadening of the bands.
(
Absence of main characteristics bands in the supported
samples indicated decomposition of Keggin structure
over the support. The band at 960 cm were attributed to
V =O of vanadium pyrophosphate supported by XRD.
The band at 989 cm corresponded to Mo=O chain. The
bands at 1212–1220 and 1356–1370 cm were assigned
to symmetric and asymmetric stretching vibrations of
the phosphate groups. This result indicated decomposi-
tion of Keggin ion of vanado-molybdophosphoric acid
over TiO after calcination. The broad and weak band at
8
–
1
4+
–
1
–
1
I
5
IV
III
2
4
–1
00–489 cm could be attributed to Ti–O–Ti.
II
3
XRD analysis. The X-ray diffractograms of the cata-
lysts (Fig. 3) [2θ = 23.33°, 27.26°, 27.32°, 27.34° (JCP-
2
DS-832388)] demonstrated the presence of (VO) P O
7
2
2
along with MoOPO phases [12, 13]. A very small peak
at 2θ = 41.18° (JCPDS-821031) indicated presence of
4
1
the active Mo(PO ) phase which was supported by the
20
30
40
ꢀșꢁꢂGHJ
50
3
3
peaks at 2θ = 45.89° and 49.30°. Probably the low con-
centration of phosphorus oxides in the catalyst was re-
sponsible for formation of the intermediate phosphate.
Typically, phosphorus oxide enhanced stability of a cat-
Fig. 3. XRD pattern of (1) VMPO-10, (2) VMPO-20, (3)
VMPO-30, (4) VMPO-40, and (5) TiO ; (I) Anatase, (II)
2
Mo(PO3), (III) MoOPO4, and (IV) (VO2)P2O7.
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RABINARAYAN SENAPATI et al.
Fig. 4. TGA profiles of (a) VMPO-10, (b) VMPO-20, (c) VMPO-30, (d) VMPO-40.
structure of heteropoly acid (water bridges). The weight
loss between 155 and 455°C indicated that PMoV was
hydrated with 28 molecules of water [14–18].
ESR spectra. At room temperature ESR spectrum of
VMPO-30 consisted of a peak of 35 G width centered at
336.823 mT. The broad isotopic signal with g = 1.9037
4
+
indicated presence of V ions characterized by unpaired
NH –TPD analysis. Pure TiO demonstrated three
3
2
3
d electrons of s = 1/2 with nuclear spin I = 7/2.
desorption peaks (Fig. 5) at 106, 332, and 604°C associ-
ated with weak, medium and strong acidity, accordingly
Catalytic activity. Study of ammoxidation of 2-, 3-,
and 4-picoline as well as o-, m- and p-xylene was carried
out using VMPO-10, VMPO-20, VMPO-30, and VMPO-
[19–21]. The catalyst acidity increased with simultane-
ous increase in strong acid sites. Upon further increase
of acidity (VMPO-30 and VMPO-40), it decreased
from strong acid site to moderate acid sites over it
4
0 catalysts (Figs. 7, 8). With increased PMoV loading,
conversion of initials and yield of products increased
from VMPO-10 to VMPO-30 and then marginally de-
creased with VMPO-40, indicating that nitrile yield was
dependent on VMPO loading. The VMPO-30 catalyst
demonstrated the most efficient catalytic activity. The
low catalytic functionality of VMPO-10 and VMPO-20
was attributed to low availability of active phases. The
higher yield of nitrile on VMPO-30 catalyst could be
(Table 1).
H –TPR analysis. In VMPO-10 and VMPO-20
2
(
Fig. 6) two reduction peaks at 460 and 770°C corre-
5
+
4+
spond to reduction of V to V species [22]. One broad
peak recorded for VMPO-30 and VMPO-40 indicated
the presence of V+4 in the active phase of (VO) P O
2
2
7
which was confirmed by XRD.
4+
due to the presence of V [23]. The important feature
TEM. The TEM images of VMPO-30 demonstrated
of the TiO support was its interaction with the active
2
the spherical morphology with average particle size
phases of phosphates and pyrophosphates of vanadium
and molybdenum (oxygen release) [24].
1
70–180 nm.
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A VERSATILE VMPO CATALYST PREPARED IN SITU
295
1
2
4
3
3
4
2
1
5
1
00 200 300 400 500 600 700 800 900
100 200 300 400 500 600 700 800 900
T, °C
T, °C
Fig. 5. NH –TPD profiles of (1) TiO , (2) VMPO-10,
Fig. 6. H –TPR profiles of (1) VMPO-10, (2) VMPO-20,
3
2
2
(3) VMPO-20, (4) VMPO-30, and (5) VMPO-40.
(3) VMPO-30, and (4) VMPO-40.
It is evident that pyrophosphates of vanadium and
phosphates of molybdenum found in the calcined VMPO
catalysts influenced on ammoxidation. The small con-
centration of phosphorus oxides in the catalysts was the
source of phosphates and pyrophosphate phases, and
also the minimum amount of vanadium was essential
for the increase of the catalytic activity in the course of
ammoxidation. Hence, the highest activity of the cata-
lyst VMPO-30 was due to presence of the phosphate and
pyrophosphate phases of Mo and V [25].
Ammonia acted as a proton acceptor for the inter-
mediate compounds of the process, provided nitrogen
atoms in formation of amide, nitrile and also acted as
a regulator of the rate and degree of oxidation reaction
of organic materials. Conversion of feed materials de-
creased as ammonia concentration was increased. Gen-
erally ammonia reduces the overall rate of oxidation of
hydrocarbons and their oxygen derivatives [26].
Effect of temperature. The effect of reaction tem-
perature on the ammoxidation of isomeric 2-, 3-, and
4-picoline and o-, m-, and p-xylene was studied with
VMPO-30 catalyst. With the reaction temperature in-
crease from 375 to 425°C, both conversion of feed ma-
The VMPO-30 demonstrated the superior and ef-
fective interactions between the support and its active
phases which was in accord with XRD results.
conv of p-xylene
yield of terephthaonitrile
conv o-xylene
yield of ortho phthaonitrile
conv m-xylene
yield of isophthaonitrile
conv 4-pic
yield 4-cp
1
00
conv 2-pic
yield 2-cp
conv 3-pic
yield 3-cp
1
00
8
6
4
2
0
0
0
0
0
8
6
4
2
0
0
0
0
0
VMPO-10 VMPO-20 VMPO-30 VMPO-40
VMPO-10 VMPO-20 VMPO-30 VMPO-40
Fig. 7. Ammoxidation of isomeric picolines on VMPO-
0–VMPO-40 (conv—conversion, pic—picoline, cp—
cyanopyridine).
1
Fig. 8. Ammoxidation of isomeric xylenes on VMPO-10–
VMPO-40.
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RABINARAYAN SENAPATI et al.
tion changed to cherry red. To this mixture, 66.5 g of
TE
sodium molybdate dissolved in 100 mL of water were
added. Finally, 45 mL of concentrated sulphuric acid
were added slowly with continuous stirring accompa-
nied by change in colour from cherry red to light red.
The PMoV was then extracted with 200 mL of diethyl
ether. After separation of the oily (middle) layer, stream
of the air was passed to make it ether free. The solid
that settled down was dissolved in water, concentrated
to the first appearance of crystals in a desiccator over
concentrated H SO , then allowed to crystallize further
Catalytic reactor
tube
MFC
MFC
Furnace
heater
wc
2
4
Gas product
and dried. Then a series of PMoV supported on TiO2
Aldrich make heated at 500°C for 3 h) catalysts were
Pump of
feeding
Air Ammonia
(
Liquid product GC
prepared in situ by varying the wt % of PMoV from 10
to 40%. The required quantity of PMoV was dissolved
in minimum amount of water and the solution was add-
Reagent
[
Feed Vessel]
Fig. 9. Experimental set up for catalytic ammoxidation
reaction. (MFC) mass flow controller; (TE) temperature
element; (wc) water condenser; (GLS) gas liquid separator,
ed to the known amount of TiO with constant stirring.
2
Excess water was removed on a hot water bath, and the
catalyst masses were dried in an air oven at 120°C for
(
GC) gas chromatograph.
8
h. Then the catalysts were calcined at 500°C for 2 h.
terials and yield of the corresponding nitriles increased.
At temperature >425°C conversion and yield decreased.
Finally, catalysts were sized to 14–18 mesh. The cata-
lysts were referred to as VMPO-10, VMPO-20, VMPO-
30, and VMPO-40 corresponding to 10, 20, 30, and 40%
PMoV respectively.
Conversion of picolines and xylenes could be listed
in the order of 4-picoline > 2-picoline > 3-picoline and
p-xylene > o-xylene > m-xylene at 425°C on VMPO-30
catalyst.
Physico-chemical characterization. FT-IR (KBr)
spectra were recorded on a Varian FTIR-800 spectropho-
tometer. X-Ray diffraction spectra were measured in the
range of 10° to 70° at a rate of 1.5 deg/min (Philips ana-
XRD of the used catalyst. XRD study of the used
VMPO-30 catalyst after 25 cycles of the process revealed
presence of the following phases: Anatase (TiO ), Rutile
lytical 3710) using CuK radiation. The Brunauer–Em-
2
α
(
TiO ) and Vanadium Molybdenum Oxide (V MoO ).
mett–Teller surface areas were measured by N adsorp-
2
2
8
2
The anatase phase was converted to rutile phase, and
different phosphates and pyrophosphates of molybdenum
and vanadium were also converted to vanadium molyb-
denum oxide phases. Hence, decrease in the conversion
of the feed material could be due to the absence of dif-
ferent phosphates and pyrophosphates of molybdenum
and vanadium.
tion on the surface of the prepared catalyst at –196°C
using a Tristar 3000 surface area analyser (Micromerit-
ics, USA). The known amount of a catalyst sample was
evacuated for 3 h at 150°C to remove the physically
adsorbed water. The acid character of the catalysts was
studied by temperature programmed desorption (TPD)
of NH3 in a Chemisorb 2720 (Micromeritics, USA).
About 1 g of the powdered sample contained in a quartz
tube was heated at 250°C for 3 h upon Ar flow. After
EXPERIMENTAL
Preparation of the catalyst. Vanado-molybdophos-
cooling the sample to room temperature, NH (0.4%
3
phoric acid; H PMo VO (abbreviated as PMoV) was
NH balanced in He) gas was passed over the sample
4
11
40
3
prepared according to the reported procedure [27]. In
brief, 3.05 g of sodium metavanadate was dissolved in
to clean the surface of the catalyst. Then analysis of the
sample was carried out upon helium flow with heating
rate 10°C/min and heated up to 900°C. The temperature
1
00 mL of boiling water, and 3.55 g of disodium hy-
drogen phosphate was dissolved in 100 mL of distilled
water separately. Both solutions were mixed together
and cooled down. Then the mixture was acidified with
programmed reduction with H of the prepared cata-
2
lyst was carried out in an AutoChem-II (Micromeritics,
USA) instrument. TGA was used to measure the weight
loss of the synthesized catalyst in the air atmosphere
5
mL of concentrated H SO till the colour of the solu-
2 4
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A VERSATILE VMPO CATALYST PREPARED IN SITU
297
with a STA449 F3 Jupiter Thermo Gravimetric Analyser
system at the rate of 5 deg/min. Transmission electron
micrograph (TEM) images of catalysts were taken by
using a TECNAI-G2 microscope with charge coupled
camera.
3. Janke, C., Radnik, J., Bentrup, U., Martin, A., and Brück-
ner, A., ACS Catal., 2014, vol. 4, p. 2687.
https://doi.org/10.1021/cs500458w
4
. Nagaraju,P.,Lingaiah,N.,SaiPrasad,P.S.,Kalevaru,V.N.,
and Martin, A., Catalysis Commun., 2008, vol. 9, p. 2449.
https://doi.org/10.1016/j.catcom.2008.06.012
Activity studies. Ammoxidation of three isomeric
picolines and three isomeric xylenes was studied in a
fixed bed continuous flow glass reactor (Fig. 9) under
atmospheric pressure. The reactor was packed with 10 g
of catalyst between two layers of porcelain beads. The
upper layer of the porcelain beads served dual purpose
as a pre-heater and mixer for the reactant. Before the
reaction, ammonia gas was fed to catalyst bed at the
rate of 50 mL/min at 450°C for 1 h. Then molar ratio
of feed: ammonia: air (1 : 3 : 6) was introduced into
the reactor. The system temperature was measured by a
thermocouple. The reactions were performed in the tem-
perature range of 375–450°C for 2 h. The liquid product
was trapped at 0°C. The products were analysed by gas
chromatography (GC), using carbowax 20 M column
with a thermal conductivity detector (TCD).
5
. Kalevaru, V.N., Madaan, N., and Martin, A., Appl. Catal.
A: Gen., 2011, vol. 391, p. 52.
https://doi.org/10.1016/j.apcata.2010.07.034
6
7
8
. Ray, S.C., Roy, S.K., Singh, B., Murty, G.S., and Mukher-
jee, P.N., Indian J. Technol., 1983, vol. 21, p. 387.
. Roy, S.K., Ray, S.C., Singh, B., and Mukherjee, P.N.,
Indian J. Technol., 1983, vol. 21, p. 461.
. Roy, S.K., Dutta, P., Nandi, L.N., Yadav, S.N., Mon-
dal, T.K., Roy, S.C., Mitra, S., and Samuel, P., J. Mol.
Catal. A: Chem., 2004, vol. 223, p. 211.
https://doi.org/10.1016/j.molcata.2004.04.046
9
. Lücke, B., Narayana, K.V., Martin, A., and Jahnisch, K.,
Adv. Synth. Catal., 2004, vol. 346, p. 1407.
https://doi.org/10.1002/adsc.200404027
1
0. Deltecheff, C.R., Aouissi, A., Bettahar, M.M., Launaym, S.,
and Fournier, M., J. Catal., 1996, vol. 164, p. 16.
https://doi.org/10.1006/jcat.1996.0358
CONCLUSIONS
11. Roch, C.M., Laronze, N., Villianneau, R., Guilou, N.,
Teze, A., and Herve, G., J. Catal., 2000, vol. 190, p. 173.
https://doi.org/10.1006/jcat.1996.0358
2. Bielanski, A., Malecka, A., and Kubelkova, L., J. Chem.
Soc., Faraday Trans., 1989, vol. 85, p. 2847.
https://doi.org/10.1039/F19898502847
13. Viswanadham, B., Srikanth, A., and Chary, K.V.R.,
J. Chem. Sci., 2014, vol. 126, p. 445.
4. Bardin, B. and Davis, R., Top. Catal., 1998, vol. 6, p. 77.
TiO Supported VMPO prepared by thermal de-
2
composition of PMoV has been found to be a versatile
catalyst. VMPO-30 Demonstrated the highest catalytic
activity for ammoxidation of three isomeric picolines
and three isomeric xylenes which could be due to the
presence of different well dispersed phases of vanadium
pyrophosphates and molybdenum phosphates.
1
1
https://doi.org/10.1023/A:1019174624875
ACKNOWLEDGMENTS
15. Deltecheff, C.R., Fournier, M., and Frank, R., Inorg.
Chem., 1983, vol. 22, p. 207.
https://doi.org/10.1021/ic00144a006
16. Damyanova, S. and Fierro, J.L.G., Chem. Mater., 1998,
vol. 10, p. 871.
The authors thank the Director, CSIR-Central Institute of
Mining and Fuel Research for his kind permission to pub-
lish the paper. The authors also thank Council of Scientific
and Industrial Research, New Delhi for financial support. The
authors are thankful to Dr. S. Maity for providing TPD and
TPR analysis of the catalysts.
https://doi.org/10.1021/cm970639a
1
7. Predoeva, A., Damyanova, S., Gaigneaux, E.M., and
Petrov, L., Appl. Catal. A: Gen., 2007, vol. 319, p. 14.
https://doi.org/10.1016/j.apcata.2006.11.007
8. Cabello, C.I., Egusquiza, M.G., Botto, I.L., and Minelli, G.,
Mater. Chem. Phys., 2004, vol. 87, p. 264.
1
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
REFERENCES
https://doi.org/10.1016/j.matchemphys.2004.04.015
9. Rodriguez, D., Adriany, C., and Gaigneaux, E.M., Catal.
Today, 2011, vol. 167, p. 56.
0. Marci, G. E., Gracia-Lopez, E., Bellardita, M.,
Parisi, F., Colbeau-Justin, C., Sorgues, S., Liotta, L.F.,
and Palmisano, L., Phys. Chem. Chem. Phys., 2013,
vol. 15, p. 13329.
1
2
1
. Chuck, R., Appl. Catal. A: Gen., 2005, vol. 280, p. 75.
https://doi.org/10.1016/j.apcata.2004.08.029
2
. Roy, S.K., Ray, S.C., Dutta, P., and Nandi, L.N., Eur.
Patent 1617946, 2006.
https://doi.org/10.1039/C3CP51142A
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 90 No. 2 2020

298
RABINARAYAN SENAPATI et al.
2
1. Rao, K.N., Lingaiah, N., Suryanarayana, I., and Sai
Prasad, P.S., Catal. Lett., 2003, vol. 90, p. 31.
https://doi.org/10.1023/A:1025860009013
2. Dutta, A., Agarwal, M., and Dasgupta, S., J. Mater.
Chem. 2002, vol. 12, p. 1892.
25. Lingaiah, N., Mohan Reddy, K., Nagaraju, P., and
Wachs, I.E., J. Phys. Chem., 2008, vol. 112, p. 8294.
https://doi.org/10.1021/jp7119476
2
2
2
2
6. Martin, A., Kalevaru, V.N., Lücke, B., and Brückner, A.,
Appl. Catal. A: Gen., 2008, vol. 335, p. 196.
https://doi.org/10.1016/j.apcata.2007.11.025
7. Tsigdinos, G.A. and Hallada, C.G., Inorg. Chem., 1968,
vol. 7, p. 437.
https://doi.org/10.1039/B200562J
3. Kalevaru, V.N., Raju, B.D., Venkat Rao, V., and Martin, A.,
Appl. Catal. A: Gen., 2009, vol. 352, p. 223.
https://doi.org/10.1016/j.apcata.2008.10.009
4. Herrmann, J. and Disdier, M., Catal. Today, 2000,
vol. 56, p. 389.
2
https://doi.org/10.1016/S0920-5861(99)00299-0
https://doi.org/10.1021/ic50061a009
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