Synthesis and characterization of AlCl3 impregnated molybdenum oxide as heterogeneous nano-catalyst for the Friedel-Crafts acylation reaction in ambient condition

Article abstract of DOI:10.1166/jnn.2015.11253

Aluminum trichloride (AlCl₃) impregnated molybdenum oxide heterogeneous nano-catalyst was prepared by using simple impregnation method. The prepared heterogeneous catalyst was characterized by powder X-ray diffraction, FT-IR spectroscopy, solid-state NMR spectroscopy, SEM imaging, and EDX mapping. The catalytic activity of this protocol was evaluated as heterogeneous catalyst for the Friedel-Crafts acylation reaction at room temperature. The impregnated MoO₄(AlCl₂)₂ catalyst showed tremendous catalytic activity in Friedel-Crafts acylation reaction under solvent-free and mild reaction condition. As a result, 84.0% yield of acyl product with 100% consumption of reactants in 18 h reaction time at room temperature was achieved. The effects of different solvents system with MoO₄(AlCl₂)₂ catalyst in acylation reaction was also investigated. By using optimized reaction condition various acylated derivatives were prepared. In addition, the catalyst was separated by simple filtration process after the reaction and reused several times. Therefore, heterogeneous MoO₄(AlCl₂)₂ catalyst was found environmentally benign catalyst, very convenient, high yielding, and clean method for the Friedel-Crafts acylation reaction under solvent-free and ambient reaction condition.

Full text of DOI:10.1166/jnn.2015.11253

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Nanoscience and Nanotechnology
Vol. 15, 8243–8250, 2015
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Synthesis and Characterization of AlCl3
Impregnated Molybdenum Oxide as Heterogeneous
Nano-Catalyst for the Friedel-Crafts Acylation
Reaction in Ambient Condition
Arvind H. Jadhav, Amutha Chinnappan, Vishwanath Hiremath, and Jeong Gil Seo∗
Department of Energy and Biotechnology, Energy and Environment Fusion Technology Center, Myongji University,
Myongjiro 116, Cheoin-gu, Yongin-si, Gyeonggi-do 449-728, South Korea
Aluminum trichloride (AlCl3ꢀ impregnated molybdenum oxide heterogeneous nano-catalyst was pre-
pared by using simple impregnation method. The prepared heterogeneous catalyst was character-
ized by powder X-ray diffraction, FT-IR spectroscopy, solid-state NMR spectroscopy, SEM imaging,
and EDX mapping. The catalytic activity of this protocol was evaluated as heterogeneous catalyst
for the Friedel-Crafts acylation reaction at room temperature. The impregnated MoO4(AlCl2ꢀ2 cata-
lyst showed tremendous catalytic activity in Friedel-Crafts acylation reaction under solvent-free and
mild reaction condition. As a result, 84.0% yield of acyl product with 100% consumption of reactants
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in 18 h reaction time at room temperature was achieved. The effects of different solvents system
IP: 50.35.184.159 On: Fri, 04 Dec 2015 12:20:22
Copyright: American Scientific Publishers
with MoO4(AlCl2ꢀ2 catalyst in acylation reaction was also investigated. By using optimized reac-
tion condition various acylated derivatives were prepared. In addition, the catalyst was separated
by simple filtration process after the reaction and reused several times. Therefore, heterogeneous
MoO4(AlCl2ꢀ2 catalyst was found environmentally benign catalyst, very convenient, high yielding,
and clean method for the Friedel-Crafts acylation reaction under solvent-free and ambient reaction
condition.
Keywords: MoO4(AlCl2ꢀ2 Nano-Catalyst, Friedel-Crafts Acylation, Solvent-Free and Ambient
Condition, Green Chemistry.
1. INTRODUCTION
on green chemistry, environmentally benign processes
should be developed to improve the green credentials
of the reaction.12–18 For the development of greener
processes, moisture-insensitive and easy to handle solid
acid catalysts are desired.19–22 Furthermore, the use of
solid acid catalysts offers facile catalyst recovery and
recycling, as well as product separation. At the same
time, the catalyst recovery also decreases contamina-
tion of the desired products with hazardous or harmful
metals.8–13
Indeed, solid supported catalysts are attracting more
consideration in organic reactions because of their ease
of handling in work-up procedure, good selectivity,
high yields, low cost, and reusability in compar-
ison with their homogeneous catalysts for Friedel-
Crafts acylation reaction.1–5 Several solid acid catalysts
Friedel-Crafts acylation reactions of aromatic compounds
with acid chlorides are considered as fundamental and
very important processes in organic synthesis as well
as in industrial chemistry.1–4 Traditionally, these reac-
tions require large amount of anhydrous strong Lewis
acids, such as AlCl3, TiCl3, FeCl3, or SnCl4, more than
stoichiometric amounts.5–8 These methods suffer from
toxicity and corrosion of the catalysts, generation of
a large amount of waste, and difficult purification of
products.9–11 Moreover, these catalysts are highly mois-
ture sensitive and hence moisture-free reaction condi-
tions are required to achieve the optimal yields of the
desired aromatic ketones.1–4 With the increasing emphasis
∗Author to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 10
1533-4880/2015/15/8243/008
doi:10.1166/jnn.2015.11253
8243

Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
Jadhav et al.
have been investigated for the Friedel-Crafts acylation
reactions, such as metal triflate loaded SBA-15, meso-
porous superacid catalyst, zeolite, hybrid zeolitic meso-
structured materials, modified clay, nafion-silica composite
materials, mesoporous sulphated zirconia, and meso-
porous AlKIT-5.14–25 Although interesting results have
been achieved for the Friedel–Crafts acylation reaction,
they have not led to any very important industrial applica-
tion. Friedel-Crafts acylation reaction could be performed
under solvent-free reaction condition using a solid hetero-
geneous catalyst without addition of co-catalysts in mild
reaction conditions such process would be eco-friendly and
safe.19–22
New and improved catalytic protocols continue to attract
the attention of industries/chemical laboratories due to a
very high importance of the aromatic ketones which are
key intermediates in several fields including fine chemi-
cals and pharmaceuticals.1–5 Hence, there is still a demand
for developing new synthetic methods for carrying out
the Friedel-Crafts acylation, which deal with moisture-
insensitive catalysts and efficient product/catalyst isola-
tion procedure.14–25 Solvent-free Friedel-Crafts acylation
reaction with impregnated heterogeneous catalyst leads to
new eco-benign reaction procedures that save and main-
tain green reaction procedure.14–19 The Lewis acids such
as TiCl3 and FeCl3 impregnated with some other metals
2. EXPERIMENTAL DETAILS
2.1. Preparation of MoO4(AlCl2)2 Catalyst by
Impregnation Method
Ethanol (20 ml) was taken in a two necked round bot-
tom flask under nitrogen atmosphere. Anhydrous alu-
minum chloride (AlCl3ꢀ (1.89 g, 0.014 mol) (Aldrich,
99.0%) was added into it and stirred at room temper-
ature till a clear solution formed. Ammonium molyb-
date (1.25 g, 0.0101 mol) (Aldrich, 99.0%) was added to
it under nitrogen atmosphere. The reaction mixture was
ꢀ
stirred under reflux at 100 C and kept under nitrogen
atmosphere by passing nitrogen gas (99.999%) at the rate
of 10 ml/min forꢀ 12 h. Ethanol was evaporated on rotary
evaporator at 80 C and solid dry mass was obtained. The
obtained solid mass was calcined in nitrogen atmosphere
ꢀ
at 400 C up to two hours. The HCl gas librated dur-
ing reflux process was determined by acid base titration
and librated amount of HCl in millimole was estimated
and then the catalyst was tested for the Friedel-Crafts
reaction.
2.2. Catalyst Characterization
FT-IR spectra of prepared catalysts were taken on a
Varian 2000 IR spectrometer (Scimitar series) by using
KBr disc method. Powder X-ray diffraction (XRD) pat-
terns of the catalysts were recorded on a Rigaku Mini-
such as molybdenum which shows the complex formation
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flex (Rigaku Corporation, Japan) X-ray diffractometer
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with Lewis acids are unique heterogeneous catalysts for
using Ni filtered Cu Kꢁ radiation (ꢂ = 1ꢃ5406 Å) with
14–25
Copyright: American Scientific Publishers
a 2ꢀ min−1 scan speed and a scan range of 10–60ꢀ
at 30 kV and 15 mA. The surface morphology of
MoO4(AlCl2ꢀ2 catalyst was studied by scanning elec-
tron microscopy (SEM) using a Hitachi, S-3500N SEM
instrument. Energy Dispersive X-Ray spectrometry (EDX)
were determined using SEM instrument combined with an
INCA instrument for energy dispersive X-ray spectroscopy
scanning electron microscopy (EDX-SEM), with scan-
ning electron electrode at 20 kV. The prepared acylated
the Friedel–Crafts acylation reaction.
These catalysts
have their original Lewis acidity and they gain the het-
erogeneous property with impregnation with other metals
and such catalysts were utilized in organic reactions.8–12
These reactions shows various advantages over traditional
reactions in organic solvents, such reactions are reducing
the load of organic solvent disposal and enhance the rate
of many organic reactions and reuse of catalyst.5–12 There-
fore, the development of an environmental benign het-
erogeneous catalytic using impregnation method which is
more efficient, highly selective, and less expensive for the
Friedel-Crafts acylation reaction under solvent-free condi-
tion is highly anticipated.
In the present study, we report preparation of heteroge-
neous AlCl3 impregnated molybdenum oxide nano-catalyst
and its application to Friedel-Crafts acylation reaction
under solvent-free condition. The prepared heterogeneous
catalyst was characterized by using different analytical and
spectroscopic methods. The fruitfully prepared and char-
acterized catalyst was utilized in acylation reaction. As
results, the catalyst showed 84% yield of respective acy-
lated product in 18 h reaction time at room temperature
in solvent-free condition. In addition, effect of amount
of catalyst and other solvent effects with this protocol
were determined. We have also evaluated the possibility
of regeneration of catalyst and recyclability test in Friedel-
Crafts acylation reaction.
140
130
120
110
100
90
80
Used MoO4(AlCl2)2
MoO4(AlCl2)2
70
Pure AlCl3
Pure ammonium molybdate
60
50
0
500 1000 1500 2000 2500 3000 3500 4000 4500
Wavelength(cm–1
Figure 1. FT-IR analysis of MoO4(AlCl2ꢀ2 catalyst.
J. Nanosci. Nanotechnol. 15, 8243–8250, 2015
)
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Jadhav et al.
Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
2.3. Friedel-Crafts Acylation Reaction
The Friedel-Crafts acylation of Anisole (1 g, 9.26 mmol)
(Aldrich, 99.0%) with propionyl chloride (5 equiv.)
(Aldrich, 99.0%) using the prepared MoO4(AlCl2ꢀ2
(5 wt%, 10 mg) catalyst was carried out in a magnet-
ically stirred two-necked round bottom flask fitted with
ꢀ
a guard tube (CaCl2ꢀ, activated at 150 C for 2 h. The
present reaction mixture stirred at room temperature up to
the completion of reaction. Reaction progress was mon-
itored by thin layer chromatography (TLC). After com-
pletion of the reaction, reaction mixture was filtered and
solid catalyst was separated out. The separated solid cat-
alyst can be recycled in next attempt of Friedel-Crafts
acylation reaction. The reaction mixture was washed with
dichloromethane (DCM) and water, the same process was
done triplicate and collected the organic layer. The organic
layer was then dried over anhydrous sodium sulfate and
concentrated on rotary evaporator and crude acylated prod-
uct was obtained and purified on column chromatography.
3. RESULTS AND DISCUSSION
3.1. Catalyst Characterization
FTIR spectroscopic analysis of MoO4(AlCl2ꢀ2 catalyst,
pure ammonium molybdate, and pure AlCl3 catalyst were
performed in order to determine any alterations in the FT-
IR pattern of MoO4(AlCl2ꢀ upon grafting process and
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Figure 2. EDX pattern of catalyst MoO (AlCl2 ꢀ2.
results are showed in Figure 1. The prepared catalyst
4IP: 50.35.184.159 On: Fri, 04 Dec 2015 12:20:22
scanned IR range between 400–4000 cm−1 and showed
major peaks at 1720, 1373, 1199, 910, 994, and 621. The
Copyright: American Scientific Publishers
products were compared with the authentic samples and
characterized by the 1H NMR and 13C NMR spec-
troscopy on Bruker spectrometer 400 MHz at ambient
temperature.
peaks at 994 and 910 resembles the presence of Mo
O
and Mo–O–Mo vibrational stretching in MoO4(AlCl2ꢀ2
catalyst.26 In addition, the similar peaks we observed in
Figure 3. Scanning electron microscopic analysis of MoO4(AlCl2ꢀ2 catalyst.
J. Nanosci. Nanotechnol. 15, 8243–8250, 2015
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Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
Jadhav et al.
pure ammonium molybdate spectra. On the other hand,
the absence of broad band between 3400–3600 cm−1 and
absence of sharp peak at 900 cm−1 indicates the absence
of hydroxyl and amine groups in prepared MoO4(AlCl2ꢀ2
catalyst.27 Peaks at 638, which attributed for the Al–Cl
bonding is present in the both pure AlCl3 spectrum and IR
spectrum of catalyst.27 Which indicate the presence of alu-
minum impregnation on prepared MoO4(AlCl2ꢀ2 catalyst.
To study the structural modifications in recycled catalyst,
we also carried out the IR spectra of recycled catalyst and
all similar types of bands were also observed in recycled
catalyst after being used in 6th cycle.
In order to determine the stoichiometry of
MoO4(AlCl2ꢀ2 we performed EDX scanning, Figure 2
shows the EDX pattern of prepared catalyst
Figure 5. XRD analysis of MoO4(AlCl2 ꢀ2 catalyst.
MoO4(AlCl2ꢀ2. At higher magnification, elemental com-
position was obtained by EDX analysis. An extremely
The 27Al NMR in the solid state method is uniquely
suitable to the study of Al chemistry and thus for char-
acterization of Al in various states of complexation and
good tool for the determination of the aluminium coordi-
nation number in complexes. It is well known that 27Al
NMR in the solid state shows a signal between −10 and
+20 ppm for coordination number six and between +55
and +85 ppm for coordination number four. The 27Al spec-
trum of MoO4(AlCl2ꢀ2 catalyst represented in Figure 4.
The 27Al solid state NMR spectrum of MoO4(AlCl2ꢀ2 cat-
alyst at 25 ꢀC showed a clear single line spectrum at
homogeneous distribution of Al, Mo, Cl, and O elements
throughout the MoO4(AlCl2ꢀ2 catalyst was observed by
EDX mapping. The weight percent ratio and atomic ratio
calculated from EDX analysis were equal to the expected
stoichiometry for MoO4(AlCl2ꢀ2. These results show that
the aluminium grafted molybdenum catalyst was prepared
successesfully and it was agreed with the secondary
support of IR, XRD diffraction and SEM analysis.
The morphology and structure of MoO4(AlCl2ꢀ2 cata-
lyst were investigated using SEM analysis. Figure 3 shows
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the morphology of catalyst, which exhibit well-defined
IP: 50.35.184.159 On: Fri, 04 Dec 2015 12:20:22
nanostructure with ten and five microns in size. The
SEM images show that well dispersed powder through-
out the surface. In addition, we observed the surface of
our MoO4(AlCl2ꢀ2 catalyst which indicate the amorphous
AlCl3 impregnated on molybdenum oxide, which exhib-
ited the active component disperses very evenly on the
surface of MoO4(AlCl2ꢀ2 catalyst. In 100 ꢄm and 50 ꢄm
pictures we can see the overall particle shapes of catalyst,
these particles shapes can be seen close rambles in pic-
ture 20 ꢄm and 10 ꢄm. At 10 ꢄm and 5 ꢄm we can see
the catalyst particle surface which specify the impregnated
MoO4(AlCl2ꢀ2 catalyst.
Copyright: American Scientific Publishers
−12.01 ppm, which showed the highly active tetrahedral
form of 27Al is present in the catalyst. The absence of peak
in the range of +55 and +85 ppm attributed the absence
Table I. Friedel-Crafts acylation reaction using MoO4(AlCl2ꢀ2 in
solvent-free condition and effect of other solventsa.
O
O
MoO4(AlCl2)2, catalyst
+
O
Cl
RT, Solvent free
O
(2)
(3)
(1)
MoO4(AlCl2 ꢀ2
Time Yieldb
Entry
Solvent
(equiv)
Temperature
(h)
(%)
1
2
3
4
5
6
7
8
–
–
–
–
–
–
–
–
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
48
12
14
14
14
15
18
12
18
18
12
12
18
–
1.0
0.5
0.4
0.3
0.2
0.1
0.1
0.1
0.1
0.1
0.1
0.1
86
86
85
86
86
84
27
42
22
48
31
24
Benzene
Tetrahydrofuran
1,4-dioxane
Methanol
Dichloromethane
Acetonitrile
9
10
11
12
13
Notes: aAll reactions were carried out on 1.0 mmol scale of substrate with 0.1–1.0
equiv. of MoO4(AlCl2ꢀ2 catalyst, accordingly in 4.0 ml solvent and without solvent.
bYield refers to the isolated product.
Figure 4. 27Al solid state NMR analysis of MoO4(AlCl2ꢀ2 catalyst.
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Jadhav et al.
Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
Table II. Preparation of various acylated derivatives using MoO4(AlCl2ꢀ2 catalyst in solvent-free conditiona .
Sr. No
Ar-H
Acid Halide
Time (h)
18
Product
Yieldb(%)
84
1
16
14
72
72
2
3
4
5
16
22
80
67
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Copyright: American Sc8ientific Publishers
6
7
87
81
12
6
8
9
76
71
9
10
11
14
69
18
76
Notes: aAll reactions were carried out on 1.0 mmol scale of substrate with catalyst (except Entry 1) and without addition of any co-catalyst and solvent;
bYield refers to the isolated product.
J. Nanosci. Nanotechnol. 15, 8243–8250, 2015
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Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
Jadhav et al.
of octahedral form in the prepared MoO4(AlCl2ꢀ2 catalyst.
According to a study, the peak at 0.0 ppm is attributed
to six-coordinate Al species. This peak appears from air
contamination when the catalysts were placed in an NMR
cell. This cell was manipulated under ambient air and it
does not protect entirely the catalyst from moisture.
Figure 5 shows the 2-D X-ray diffraction spectra of
MoO4(AlCl2ꢀ2 catalyst. We performed the XRD pattern
between 0–80ꢀ, to determine the crystalline structure of
catalyst, unfortunately catalyst does not have any strong
diffraction peaks in the range of 2ꢅ = 0–80ꢀ. The broad
hump at the range of 2ꢅ = 18–25ꢀ is belong to the molyb-
denum oxide. It can be seen that all the XRD patterns
of the catalysts are like crystalline and amorphous which
suggest that AlCl3 is impregnated on molybdenum, in
which molybdenum showed crystalline phase and AlCl3
showed the amorphous phase in prepared impregnated
MoO4(AlCl2ꢀ2 catalyst.
of respective acylated products. Therefore, from all these
results we conclude that, prepared MoO4(AlCl2ꢀ2 cata-
lyst is highly efficient for Friedel-Crafts acylation reaction
under solvent-free condition.
Table II shows various Friedel-Crafts acylation reac-
tion products of structurally varied arenes and acid chlo-
rides of using optimized reaction condition in presence of
MoO4(AlCl2ꢀ2 catalyst. Entry 1 shows the results of model
reaction products which were used to establish the opti-
mized reaction condition. Entries 2, 3, 4, and 5 shows the
results of substituted anisole with different structures of
acid chlorides, all yields of respective products are effi-
cient in corresponding reaction time with MoO4(AlCl2ꢀ2
catalyst. In addition, we tried to determine the reaction
with five membered arenes “thiophene” with different acid
chlorides. Results showed that, present catalyst is able to
perform Friedel-Crafts acylation reaction efficiently with
five membered rings in good yield at ambient condition
(Entries 6, 7, 8). Entries 9, 10, 11 shows the results
of acylated products of substituted thiophene with differ-
ent acid chloride, all reactions were performed smoothly
and obtained good to efficient yield with impregnated
MoO4(AlCl2ꢀ2 catalyst in solvent-free condition. These
observations encourage us to study the reaction mecha-
nism with prepared MoO4(AlCl2ꢀ2 catalyst in solvent-free
condition.
3.2. Friedel-Crafts Acylation Reaction Using
MoO4 (AlCl2)2 Catalyst
Table
I exhibits the Friedel-Crafts acylation reac-
tion of anisole (1) with propionyl chloride (2) using
MoO4(AlCl2ꢀ2 in solvent-free condition as a model reac-
tion using various reaction conditions with catalyst.
Initially, we performed catalyst free and solvent-free acy-
lation reaction of (1) and (2) at room temperature for
two days and we observed that, this reaction fails to give
Figure 6 shows the plausible reaction mechanism
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of Friedel-Crafts acylation reaction with impregnated
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MoO4(AlCl2ꢀ2 catalyst under solvent-free condition.
any desired product (entry 1). Further, to determine the
Copyright: American Scientific Publishers
catalytic activity of MoO4(AlCl2ꢀ2 at room temperature,
number of reactions were performed in solvent-free con-
dition. Primarily, we discovered the minimum amount of
MoO4(AlCl2ꢀ2 required for rapid acylation reaction by car-
rying out the catalyst dosage using 1, 0.5, 0.4, 0.3, 0.2, and
0.1 equiv. of MoO4(AlCl2ꢀ2 at uniform reaction condition
(entry 2-7) and we found that all reactions were progressed
efficiently and provide excellent yield of respective acy-
lated product (3) in 18 h reaction time, these reactions
showed the significant catalytic activity of MoO4(AlCl2ꢀ2
catalyst. In view of, the mole economy ratio of catalyst
we selected to use 0.1 equiv. of MoO4(AlCl2ꢀ2 for fur-
ther study of the Friedel-Crafts acylation reaction under
solvent-free condition.
In addition, we also carried out Friedel-Crafts acyla-
tion reaction using various solvents with MoO4(AlCl2ꢀ2
catalyst to study the effect of these solvents on acylation
reaction of (1) and (2). Entries 8 and 9 show acylation
reaction with prepared catalyst in benzene and tetrahy-
drofuran and were observed very sluggish reaction and
provided only 27% and 48% yield of desired product in
respective reaction period. However, solvents such as 1,4-
dioxane and methanol were also found to be inactive for
this protocol and showed only 22% and 48% yield (entry
10 and 11). On the other hand, Entry 13 shows the acy-
lation results in dichloromethane and acetonitrile in pres-
ence of catalyst and was showed 31% and 24% yield
O
H2
2R C
2 Ar-H
C
+
HCl
Ar
O
C
Mo+6
Mo+4 Cl
+ +Cl
2R-CH2
O
2R-CH2
C Cl
Case-I Reaction Mechanism with Molybdate Oxide
O
H2
2R C
2 Ar-H
C
Ar
+
O
HCl
AlCl(X)
C+
+
2R-CH2
AlCl(X+1)
O
2R-CH2 C Cl
Case-II Reaction Mechanism with Aluminum Chloride
Figure 6. Plausible reaction mechanism of Friedel-Crafts acylation
reaction with impregnated MoO4(AlCl2 ꢀ2 catalyst under solvent-free
condition.
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Jadhav et al.
Synthesis and Characterization of AlCl3 Impregnated Molybdenum Oxide as Heterogeneous Nano-Catalyst
morphology of prepared catalyst were characterized by FT-
IR, XRD, SEM, EDX, and solid-state NMR spectroscopy.
MoO4(AlCl2ꢀ2 catalyst after successful characterization
applied as heterogeneous catalyst for the Friedel-Crafts
acylation reaction. The present catalytic system showed
100% conversion and achieved 84% yield of respective
acylated product at room temperature using 0.1 equiv.
of catalyst in solvent-free condition. Various acylated
derivatives were prepared by using optimized reaction
condition with MoO4(AlCl2ꢀ2 catalyst at optimized reac-
tion condition. In addition, a proposed mechanism path
100
80
60
40
20
0
1
2
3
4
5
6
way also draw to understand the reaction path way with
MoO4(AlCl2ꢀ2 catalyst. The prepared MoO4(AlCl2ꢀ2 cat-
alyst can be recycled by simple filtration process at end
of the reaction and reused several times without con-
siderable loss of catalytic activity and selectivity. The
results demonstrate that the impregnated MoO4(AlCl2ꢀ2
catalyst is an excellent environmentally benign solid cat-
alyst for the Friedel-Crafts Acylation reaction in ambient
condition.
Cycles
Figure 7. Recyclability test of MoO4(AlCl2ꢀ2 catalyst in Friedel-Crafts
acylation reaction under solvent-free condition.
We believed that the present catalyst could participate in
mechanism in two different ways. In case-I, the Mo6+
present in MoO4(AlCl2ꢀ2 catalyst helps to the formation
of acyl cation from the acid chloride and molybdenum
complex, which on reaction with the aromatic substrate
leads to the formation of the acylated product and Mo+6
is regenerated as showed in case-I. On the other hand, the
AlClx present in the catalyst might be helping to the for-
mation of acylated product in presence of MoO4(AlCl2ꢀ2
catalyst as shown in case-II.
Acknowledgment: This work was supported by Basic
Science Research Program through the National Research
Foundation of Korea (NRF) funded by the Ministry of
Education (Grant number: NRF-2013R1A1A2060638) and
2014 Research fund of Myongji University.
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3.3. Recyclability Test of Heterogeneous
References and Notes
Copyright: American Scientific Publishers
MoO4(AlCl2)2 Catalyst
1. J. Deutsch, A. Trunschke, D. Muller, V. Quaschning, E. Kemnitz,
and H. Lieske, Catal. Lett. 88, 9 (2003).
Catalyst reusability is one of the important factors for eco-
nomical operation for organic transformation using het-
erogeneous catalyst, as this can allow reduction in the
operating cost and environmental pollution. After first run
of Friedel-Crafts acylation reaction, catalyst was removed
from the reaction mixture by filtration process. The filtered
catalyst was reused directly after washing with ethanol.
Catalyst was reused for the next six cycles with the
same reaction parameters which were used for fresh cat-
alyst assisted acylation reaction. The results of catalyst
reusability study has been depicted in Figure 7 and it
was found that almost similar yield can be obtained up to
fourth run i.e., acylated yield only marginally decreased
from 84 to 78%. After the fifth run, catalyst activity
started decreasing significantly and 62% yield of respec-
tive product was obtained in sixth run. Hence, the cat-
alyst is efficiently recycled for up-to six cycles without
considerable loss in its catalytic activity and selectivity
in the Friedel-Crafts acylation reaction under solvent-free
condition.
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4. CONCLUSIONS
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Received: 30 July 2014. Accepted: 2 December 2014.
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