Catalytic synthesis of 2-(1-cyclohexenyl)cyclohexanone by mixed heteropoly acids catalyst (PW12 + PMo12/SBA-15)

Article abstract of DOI:10.14233/ajchem.2014.16770

Mixed heteropoly acids (phosphotungstic acid and phosphomolybdic acid) supported on SBA-15 (PW₁₂ + PMo₁₂/SBA-15) by impregnation method was used as catalysts of self-condensation reaction of cyclohexanone to synthesize the 2-(1-cyclohexenyl)cyclohexanone. The experimental results indicated that the mixed heteropoly acids supported on SBA-15 had effective catalytic performance, which catalytic synthesis of 2-(1-cyclohexenyl)cyclohexanone. The effects of various parameters on the conversion ratio such as the amount of catalyst, loading amount, reaction time and reaction temperature were investigated. The optimum reaction conditions were as follows: The loading of the PW₁₂ + PMo₁₂/SBA-15 was 29%, the percentage of catalyst in reactants was 3%, the reaction time was 2.5 h and the reaction temperature was 150°C. The conversion rate could reach 86.5%.

Full text of DOI:10.14233/ajchem.2014.16770

Asian Journal of Chemistry; Vol. 26, No. 21 (2014), 7343-7347
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.16770
Catalytic Synthesis of 2-(1-Cyclohexenyl)cyclohexanone by
Mixed Heteropoly Acids Catalyst (PW12 + PMo12/SBA-15)
1
1
2
1
1
1,*
YING-YING WANG , BO WU , CHUN-LI LIU , FU-XIANG LI , ZHI-PING LV and JIAN-WEI XUE
1
2
Research Institute of Special Chemicals, Taiyuan University of Technology, Taiyuan 030024, Shanxi Province, P.R. China
Shandong Hualu Hengsheng Chemical Industrial Stock Co., Ltd., Dezhou, Shandong Province, P.R. China
*
Corresponding author: Fax: +86 351 6111178; Tel: +86 13099072796; E-mail: xuejianwei@yeah.net
Received: 27 November 2013;
Accepted: 1 April 2014;
Published online: 30 September 2014;
AJC-16133
Mixed heteropoly acids (phosphotungstic acid and phosphomolybdic acid) supported on SBA-15 (PW12 + PMo12/SBA-15) by impregnation
method was used as catalysts of self-condensation reaction of cyclohexanone to synthesize the 2-(1-cyclohexenyl)cyclohexanone. The
experimental results indicated that the mixed heteropoly acids supported on SBA-15 had effective catalytic performance, which catalytic
synthesis of 2-(1-cyclohexenyl)cyclohexanone. The effects of various parameters on the conversion ratio such as the amount of catalyst,
loading amount, reaction time and reaction temperature were investigated. The optimum reaction conditions were as follows: The loading
of the PW12 + PMo12/SBA-15 was 29 %, the percentage of catalyst in reactants was 3 %, the reaction time was 2.5 h and the reaction
temperature was 150 °C. The conversion rate could reach 86.5 %.
Keywords: Catalytic, 2-(1-Cyclohexenyl)cyclohexanone, Impregnation method, Mixed heteropoly acids, SBA-15.
7
exchange resin , aluminum oxide , titanium dioxide and
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10,11
12
INTRODUCTION
13
activated carbon as the carrier of the preparation of the hetero-
poly acid composites. Most researchers believe that activated
carbon and silica as excellent carrier can be used for preparing
heteropoly acid composites. The siliceous mesoporous
materials (mainly SBA-15 and MCM-41) were applied as the
O-Phenylphenol (OPP) is one of the most important fine
chemical industrial products derived from cyclohexanone and
is widely used as fungicide, antiseptic, assistant agent in dyeing,
1,2
surface activator and thermal stabilizer etc. . The synthesis
of O-phenylphenol primarily was based on cyclohexanone as
raw material and was obtained by a two-step chemical reaction
process via condensation and dehydrogenation. And the target
1
4,15
carriers for many active substances . SBA-15 is a new type
of SiO mesoporous materials which is synthetized with a non-
2
3
ionic block polymer as the template and it not only has larger
diameter and thicker cell walls, but also has better stability.
product of self-condensation of cyclohexanone is 2-(1-cyclo-
hexenyl)cyclohexanone which can generate O-phenylphenol
by further dehydrogenation. Therefore, it is very important
for the preparation of 2-(1-cyclohexenyl) cyclohexanone. Self-
condensation reaction of cyclohexanone belongs to nucleo-
philic substitution reaction on α-carbon atom, which can not
1
6
Wang et al. supported heteropoly acid on SBA-15 as a catalyst
had studied on the alkylation reaction of 1-dodecene in benzene
solvent and found that pure SBA-15 has no catalytic activity,
while catalytic activity, selectivity and stability of the PW12/SBA-
17
4
5
15 are better than HY zeolite. Lapkin et al. had studied the
heteropoly acid supported on SBA-15 as a chemical adsorbent
and found it has good effect. The study also found that hetero-
poly acid supported on SBA-15 has a damaging effect on the
carrier structure, even though the loading is very little.
The use of mixed heteropoly acids supported on SBA-
15(PW12 + PMo12/SBA-15) by impregnation method as solid
catalysts for self-condensation reaction of cyclohexanone to
synthesize 2-(1-cyclohexenyl)cyclohexanone was studied in
this work.
only be acid-catalyzed , but can also be alkali catalyzed .
Heteropoly acid (HPA) catalysts have received conside-
rable attentions, because of their moderate reaction conditions,
less dosage, high activity and selectivity, fast regeneration
speed, non-toxic, non-corrosiveness, operational simplicity
which are all in favor of the design of catalysts. The most
6
popular heteropoly acids are those with the Keggin structure ,
3
e.g., H PW12O40 (HPW). Heteropoly acids are polar organic
liquids and readily soluble in water and have been successfully
applied in homogeneous catalysis. Scholars have studied ion-

7
344 Wang et al.
Asian J. Chem.
micromeritics NOVA 1200e volumetric system. Transform
Infrared (FT-IR) spectra of samples were measured using a
BIO2RAD/FT3165 spectrometer at room temperature and
analyses performed using KBr pellet technique with a resolu-
EXPERIMENTAL
SBA-15 was supplied by Jilin University Chemical Works,
China. Phosphotungstic acid (Keggin structure, PW12) and
phosphomolybdic acid were supplied by Beijing Chemical
Works, China., Tetraethyl orthosilicate (TEOS) was supplied
by Tianjin Kermel Chemical Co., Ltd., China. Templating agent
EO20PO70EO20 (P123) was supplied byAldrich Chemical Co.,
Inc. Cyclohexanone and anhydrous ethanol were supplied by
Tianjin Kermel Chemical Co., Ltd., China. These reagents were
all AR. Hydrochloric acid (industrial products) was supplied
by Taiyuan Chemical Industry Group Co., Ltd., China. Catalyst
was homemade. The deionized water was made in our laboratory.
EO20PO70EO20 (P123, 2 g) were dissolved in hydrochloric
acid (2 mol/L, 80 mL) solution, heated in the constant tempe-
rature water bath and stirred for about 3 h; after it was comp-
letely dissolved, tetraethyl orthosilicate (TEOS, 4.5 mL) was
added and stirred for 3-5 h in water bath, then dried of crysta-
llization at 100 °C for 48 h in the autoclave. The samples were
washed repeatedly until neutral and then dried at ambient
temperature, finally calcined at 550 °C for 6 h in static air.
Lastly, the pure sample of SBA-15 is obtained.
-1
tion at 2 cm . Gas Chromatography (GC) spectrum of dimer
was obtained by GC-900 which was supplied by Shanghai
Analysis Instrument Factory Co., Ltd., China.
The reaction products were separation by means of disti-
llation, the structure of product determined by infrared spectrum
(
IR) and its content was determined by gas chromatography
GC). The progress of the reaction was indicated by conversion
(
of cyclohexanone. The conversion of cyclohexanone W was
W = (A-B)/A × 100 %, where A and B was volume of cyclo-
hexanone (unit is mL). TheA was the volume of cyclohexanone
before the reaction and the B was the volume of cyclohexanone
after the reaction.
RESULTS AND DISCUSSION
The XRD patterns of pure SBA-15 and different concen-
trations of PW12 + PMo12/SBA-15 are shown in Fig. 1.As shown
in Fig. 1, for all the samples the hexagonal structure of SBA-
A mixed solid of phosphotungstic acid and phospho-
molybdic acid (weight ratio 1:1) were added to deionized water
1
5 is confirmed by a typical XRD pattern consisting of a strong
peak (at 2q around 0.8°) along with two weak peaks (at 2q
around 1.6° and 1.8°) and the characteristic crystal plane (100)
plane, (110) plane, (200) plane are clearly visible. When the
mixed heteropoly acids loading is low (3 %), zeolite SBA-15
crystal surface of the characteristic peaks almost has no change,
which indicated that a little amount of mixed heteropoly acid
ions did not have much impact on the pore of zeolite SBA-15
and it is more evenly distributed on its surface. With increasing
of the loading amount of PW12 + PMo12/SBA-15, the three
characteristic peaks of zeolite SBA-15 crystal surface have
different degree of decreasing. The reason is that with incre-
asing of the heteropoly acid loading, the pores of SBA-15 are
partially clogged by heteropoly acid ions, which leads to redu-
cing inner diameter of the pore.
(40 mL) and stirred to dissolve completely. The calcined SBA-
15 (4 g) was added to heteropoly acid solution and then stirred
with water bath at 30 °C for 24 h. After filtering and drying,
activate the sample at 300 °C for 1 h. Mixed heteropoly acids
catalyst was denoted by X % PW12 + PMo12/SBA-15, which X
represents the mass percentage share of mixed heteropoly acid
in sample.
The synthesis reaction was conducted in a three-necked
flask (250 mL) with a thermometer, a reactor, a water separator
and a reflux condenser; the mixture of the (80 mL) cyclohexa-
none and catalyst were added into a three-necked flask (250
mL). They were heated, refluxed under 145-150 °C and reacted
for some times. In this reaction, the production of water was
brought out by the condensation method of evaporation with
18
the help of cyclohexanone , which facilitates the reaction to
be in the positive direction. In addition to bringing out of the
water, part of unreacted cyclohexanone was continued to react
under reflux. After the reaction finished, the catalyst was
recovered by filtration and the distillate that boiling point at
A: SBA-15
B: 3.0% PW12 + PMo /SBA-15
12
C: 6.0% PW12 + PMo /SBA-15
12
D: 12% PW12 + PMo /SBA-15
12
64-67 °C (vacuum degree of 0.09 MPa) was collected by disti-
E: 15% PW12 + PMo /SBA-15
12
llation with a pressure-relief device. Then the colorless and
transparent cyclohexanone, which is unreacted, was obtained.
Finally, the distillate whose boiling point was 132-135 °C was
collected by distillation with a pressure-relief device.
A
B
Detection method: Samples were analyzed by different
techniques. X-ray diffraction (XRD) patterns of the catalyst
were obtained by Japanese Rigaku motor X-ray diffractometer
C
D
(Rigaku D/2500 X-Ray diffractometer) instrument operating
at 40 kV and 100 mA with Cu target K -ray irradiation. Fourier
α
Thermo Gravimetric Analyzer (TGA) were conducted under
an air flow using a Rigaku thermal analyzer with 10 °C/min
ramp for the determination of the material quality changes
with temperature, in the temperature range of 30-700 °C. The
specific surface areas were determined from the nitrogen
adsorption/desorption isotherms (at 77 °K) measured with a
E
0.5
1.0
1.5
(°)
Fig. 1. XRD patterns of SBA-15(A) and X % PW12 + PMo12/SBA-15
2.0
2.5
2θ

Vol. 26, No. 21 (2014)
Catalytic Synthesis of 2-(1-Cyclohexenyl)cyclohexanone 7345
To further ascertain the structural properties of the catalyst,
the adsorption-desorption isotherm of nitrogen analysis is
carried out on the PW12 + PMo12/SBA-15 (29 %). Fig. 2 shows
the PW12 + PMo12/SBA-15 (29 %) of nitrogen adsorption-
desorption isotherms. The figure shows adsorption and desor-
ption branches all have a steep jump branch and appear obvious
hysteresis loops in a relatively high pressure area, both of them
can not overlap and forming a ring. This phenomenon indicates
that the samples will not only have a relatively neat uniform
pore, but also have relatively large pore. Pore size distribution
197 °C
TG
was shown in Fig. 3 and it shows that the pore size of PW12
PMo12/SBA-15 (29 %) is significantly smaller than pure SBA-
5, which proved that mixed heteropoly acids had already
existed in the mesoporous zeolite.
+
DTA
1
0
200
400
600
800
1000
700
600
500
400
300
200
100
Temperature (°C)
Fig. 4. TG-DTA patterns of SBA-15
560 °C
TG
0.0
0.2
0.4
0.6
0.8
1.0
DTA
P/P0
Fig. 2. N
2
adsorption isotherms of PW12 + PMo12/SBA-15 (29 %)
54 °C
8
7
6
5
4
3
2
1
0
100
200
300
Temperature (°C)
Fig. 5. TG-DTA patterns of PW12 + PMo12/SBA-15 (29 %)
400
500
600
700
Comparing different TG/DTA curves, it is concluded that the
structure of mixed heteropoly acid loading on the support of
SBA-15 is damaged and the reduction of temperature is the
strong evidence that heteropoly acids and the carrier interact
with each other.
Effect factors of conversion rate: Fig. 6 shows there is
an increase in the conversion rate of the cyclohexanone with
the loading amount increasing. The conversion rate is the
highest when the loading amount is 29 %. While the amount
above 29 %, the reactions conversion rate were not distinctly
increased. It is well-known that the more loadings amount is,
the smaller pore volume of the carrier is. Then reactants are
limited to enter into the pore of catalyst. Thereby, the conver-
sion of the product decreases gradually.
0
1
10
100
Pore diameter (nm)
Fig. 3. Pore size distribution of PW12 + PMo12/SBA-15 (29 %)
Figs. 4 and 5 show the TG-DTA curves for pure SBA-15
and 29 % PW12 + PMo12/SBA-15. As shown in Fig. 4, the
exothermic peak appeared at 197 °C attributed to the removal
of templating agent P123 from SBA-15, which is corresponded
to the significantly weight loss at 197 °C in TG curve. Fig. 5
shows that it has an endothermic peak at 54 °C where the
The role of the catalyst is to reduce the activation energy
of the reaction, which ultimately contributes to crossing the
energy barrier more easily and generating products more
quickly.As can be seen from the Fig. 7, conversion rate increases
with the increasing amount of catalyst. Greater the amount of
catalyst is, the higher the conversion rate is. However, when
the amount of catalyst is excessive, it can help reduce the
activation energy of the side-reaction and promote the adverse
physically adsorbed water lost from (29 %) PW12 + PMo12
/
SBA-15 and an abroad exothermic peak appeared at 560 °C
where the structure of mixed heteropoly acids is destroyed.

7
346 Wang et al.
Asian J. Chem.
90
80
70
60
50
40
90
80
70
60
50
40
10
15
20
Loading amount (%)
Fig. 6. Effect of loading amount on conversion
25
30
35
110
120
130
Temperature (°C)
Fig. 8. Effect of reaction temperature on conversion
140
150
160
9
0
5
90
85
80
75
70
65
60
55
50
45
8
80
75
70
65
60
55
50
1.0
1.5
2.0
Reaction time (h)
Fig. 9. Effect of reaction time on conversion
2.5
3.0
3.5
1
.0
1.5
2.0
Amount of catalyst (%)
Fig. 7. Effect of quantity of catalyst on conversion
2.5
3.0
3.5
Product analysis and identification: The test of the
reactions. Fig. 7 shows the amount of catalyst is 3 % for the
optimum condition.
samples selected hydrogen flame ionization detector (FID),
quartz capillary column (OV-1 type).The temperature of chroma-
tographic column: 220 °C; vaporization temperature: 250 °C;
detection temperature: 260 °C; column pressure: 0.15 MPa;
sample size is 0.5 µL; sample shunt rate: 10 mL/min. GC spectrum
of dimer was showed in Fig.10. We could see three different
peaks from the Fig. 10 as follows: Peak of the cyclohexanone
at around 2 min; peak of 2-(1-cyclohexenyl) cyclohexanone
at around 4.17 min; peak of 2-cyclohexyl alkylene cyclohexa-
none at around 4.28 min. And the peak areas of 2-(1-cyclo-
hexenyl)cyclohexanone was largest, which indicated the largest
amount of 2-(1-cyclohexenyl)cyclohexanone.
Temperature is considered as an important factor to con-
version rate. Raising the temperature is apparently favourable
for the acceleration of the forward reaction. From Fig. 8, it is
found that when the temperature reaches 150 °C, conversion
rate can reach to a high value. With further increasing of the
temperature, the conversion rate does not increase, even decrease.
When the temperature surpassed 150 °C, the conversion rate
reduced evidently which explained that high temperature could
prompt the production of by-products. Therefore, the optimum
reaction temperature should be selected at 150 °C. At the same
time, the reaction time also played an important role in the
conversion rate. Fig. 9 indicates that there was a variation in
the conversion rate with the increasing of reaction time. The
longer the reaction time was, the higher the conversion rate of
the cyclohexanone. When the reaction time is 2.5 h, the
conversion rate reached 86.5 %. When the reaction time is 3
h, the conversion rate of the cyclohexanone was still slightly
improved. While we take the energy factors into consideration,
the best reaction time is 2.5 h.
IR analysis: Spectroscopic method for identifying of
surface molecules usually relied on the frequency of chemical
groups or compared with standard IR spectra of the known
reference. IR spectrum of main product was shown in Fig. 11,
-1
the characteristic peaks are vested as follows: 1708.81 cm is
-1
-1
the stretching vibration of C=O; 2927.74 cm , 2858.31 cm
is the stretching vibration of the C=C in the cyclohexenyl ring;
-1
1448.44 cm is corresponding to the in-plane bending of C-H.
Compared with the standard IR spectrum of 2-(1-cyclohe-

Vol. 26, No. 21 (2014)
Catalytic Synthesis of 2-(1-Cyclohexenyl)cyclohexanone 7347
and the adsorption-desorption isotherm of nitrogen analysis
all proved when the mixed heteropoly acids were supported
on SBA-15, the pore size of SBA-15 is reduced, which proved
that mixed heteropoly acids had already existed in the
mesoporous zeolite. (2) Mixed heteropoly acid catalysts (PW12
4
3
3
2
2
1
1
00000
50000
00000
50000
00000
50000
00000
4.17
+
PMo12/SBA-15) were prepared using impregnation method,
which had greatly improved the BET surface area and catalytic
activity and also had given full play to the catalysis of hetero-
poly acids. Meanwhile, 2-(1-cyclohexenyl) cyclohexanone
with high purity could be obtained after distillation separation
and the product conversion rate of the catalytic reaction reached
86.5 %.
4.28
5
0000
0
-50000
ACKNOWLEDGEMENTS
2
4
6
Time (min)
Fig. 10. GC spectra of dimer
Jian-wei Xue and Ying-ying Wang are grateful to the
technical support team of Research Institute of Special
Chemicals, Taiyuan University of Technology.
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Conclusion
In this section, the mixed heteropoly acids supported on
SBA-15 which was used as catalysts of self-condensation
reaction of cyclohexanone to synthesize the 2-(1-cyclo-
hexenyl)cyclohexanone were studied. The effects of various
parameters on the conversion ratio were also discussed. The
experimental results show that: (1) The testing result of XRD
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