Preparation, characterization and catalyst application of ternary interpenetrating networks of poly 4-methyl vinyl pyridinium hydroxide-SiO 2-Al2O3

Article abstract of DOI:10.1016/j.jssc.2011.05.035

In this work, Al₂O₃ was mixed with SiO₂ and poly 4-vinylpyridine by the sol-gel method in order to make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation reaction. The physical and ch

Full text of DOI:10.1016/j.jssc.2011.05.035

Journal of Solid State Chemistry 184 (2011) 2009–2016
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Journal of Solid State Chemistry
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Preparation, characterization and catalyst application of ternary
interpenetrating networks of poly 4-methyl vinyl pyridinium
hydroxide–SiO2–Al2O3
Roozbeh Javad Kalbasi n, Majid Kolahdoozan n, Sedigheh Mozafari Vanani
Department of Chemistry, Shahreza Branch, Islamic Azad University, 311-86145 Shahreza, Isfahan, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work, Al2O3 was mixed with SiO2 and poly 4-vinylpyridine by the sol–gel method in order to
make a composite which is used as a heterogeneous basic catalyst for Knoevenagel condensation
reaction. The physical and chemical properties of the composite catalyst were investigated by XRD,
FT-IR, TG, BET and SEM techniques. The catalytic performance of each material was determined for the
Knoevenagel condensation reaction between carbonyl compound and malononitrile. The reactions
were performed in solvent-free conditions and the product was obtained in high yield and purity after a
simple work-up. The effects of the amount of catalyst, amount of monomer for the synthesis of
composite and recyclability of the heterogeneous composite were investigated. The composite catalyst
used for this synthetically useful transformation showed considerable level of reusability besides very
good activity.
Received 20 December 2010
Received in revised form
16 April 2011
Accepted 29 May 2011
Available online 12 June 2011
Keywords:
Polymer-inorganic hybrid material
SiO2–Al2O3
Polymeric composite
Basic catalyst
& 2011 Elsevier Inc. All rights reserved.
1. Introduction
other hand, inorganic materials show high elastic modulus, heat
resistance, corrosiveness, weather resistance, solvent resistance and
Homogeneous catalysts are soluble species that are usually
very active and selective. Their syntheses are guided by molecular
design principles, but are often difficult to use in industry. They
suffer from high costs associated with separating them from
products and consequential difficulties in recycling. The develop-
ment of heterogeneous catalysts to replace homogeneous systems
for the production of a wide range of chemicals is motivated by
several potential advantages such as easier separation of the
catalyst from the reaction medium, greater catalyst stability,
improved regenerability, eco-benignity, and fitting the concepts
of ‘‘green chemical process’’. They can be designed to give higher
activity, selectivity and longer catalyst lifetimes [1–4].
Polymer-inorganic hybrid materials obtained by combining
organic polymers and inorganic compounds at nano or molecular
order are expected to be the original material which exhibit
high performance in all properties. Both pure organic polymer and
pure inorganic materials have their own advantages and disadvan-
tages. The organic polymer materials exhibit excellent flexibility,
toughness, moldability and adhesiveness, but their heat-resistance
properties are inferior to those of inorganic materials. On the
mechanical strength. However, they are very brittle and their
moldability is very poor. Therefore, the combination of inorganic
and organic moieties in a single-phase material can lead us to tailor
the mechanical, electrical and optical properties with respect to
numerous applications [5–8] such as catalysis, adsorption, separa-
tion, drug delivery and sensing [9–17].
Sol–gel technology, which is mainly based on inorganic
polymerization reactions, is an important way to synthesize
organic–inorganic hybrid materials because of its unique low
temperature processing characteristic providing opportunities to
let organic and inorganic phases mix well and incorporate with
each other at temperatures under which the organic phase can
survive. Since the last few decades, the preparation, characteriza-
tion and application of those organic–inorganic hybrid materials
based on the sol–gel process have been the fast growing research
field in materials science [5–9,18–20].
Knoevenagel condensation is one of the well-known reactions
in organic chemistry right from the syntheses of small molecules
to the elegant intermediates of anti-hypertensive drugs and
calcium antagonists. It is generally catalyzed by weak bases like
primary, secondary, tertiary amines, ammonium or ammonium
salts under homogeneous conditions. In the last decade, a wide
range of catalysts, such as MgO [21], NbCl5 [22], MgF2 [23]
Na2CaP2O7 [24] chitosan [25], ionic liquids containing imidazole
[26] or guanidinium group [27], have been employed to catalyze
n Corresponding authors. Fax: þ98 321 3213103.
E-mail addresses: rkalbasi@iaush.ac.ir (R.J. Kalbasi),
kolahdoozan@iaush.ac.ir (M. Kolahdoozan).
0022-4596/$ - see front matter & 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2011.05.035

2010
R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
this reaction. However, the use of such catalysts is associated with
environmental pollution. In the recent years, solid basic catalysts
have received an increased attention as they facilitate a variety of
organic reactions that take place via carbanionic intermediates
[28–39].
In this paper, we report the synthesis of poly 4-methyl vinyl
pyridinium hydroxide–SiO2–Al2O3 (P4MVPH–SiO2–Al2O3) by the
in-situ polymerization of 4-vinylpyridine (4VP) in the presence of
aluminum isopropoxide and tetraethyl orthosilicate (TEOS),
subsequent quaternization with methyl iodide and ion exchange
occurs with NaOH. The novelty of this procedure is at easy
preparation together with using inexpensive materials. The basic
property of this new polymeric inorganic catalyst was tested for
Knoevenagel condensation of various aldehydes with malononi-
trile in solvent-free conditions. The composite could be easily
recovered by simple washing and filtration and reused up to
5 times without significant loss in its catalytic activity.
water to remove excess NaOH and was dried in room temperature
to yield poly 4-methyl vinyl pyridinium hydroxide–SiO2–Al2O3
(P4MVPH–SiO2–Al2O3 (in-situ)) composite.
Hydroxide content of P4MVPH–SiO2–Al2O3 composite was
estimated by back titration using NaOH (0.2 N). 10 mL of HCl
(0.2 N) was added to 0.05 g of this composite and stirred for
30 min. The catalyst was removed and washed successively with
deionized water. The excess amount of HCl was titrated with
NaOH (0.2 N) in the presence of phenol phthalein as indicator.
Basic sites content of the catalyst was 4.8 mmol gꢀ1
.
The procedure for preparing P4MVPH–SiO2–Al2O3 (in-situ) is
given in Scheme 1.
2.2.2. General procedure for Knoevenagel condensation reaction
The catalytic activity of P4MVPH–SiO2–Al2O3 was tested for
the Knoevenagel condensation. In a typical experiment, 1 mmol of
benzaldehyde (0.10 mL), 1 mmol of malononitrile (0.07 mg) and
0.12 g of catalyst (P4MVPH–SiO2–Al2O3) were taken in a round-
bottom flask, and were stirred. The reaction was carried out under
solvent-free condition at room temperature. (It should be
mentioned that in the case solid aldehydes, the mixture was
ground at room temperature in a glass mortar and pestle.) The
progress and completion of the reaction was monitored by TLC,
using n-hexane/ethyl acetate (5:1) as eluent. After 3 min of reaction,
the mixture was cooled to 10 1C, for the solidification of the product.
10 ml of hot ethanol was added to the reaction mixture and
the catalyst was separated from the reaction mixture by filtration.
The residual solid was re-crystallized with hot ethanol (5 mL). The
product was identified with 1H NMR, 13C NMR and FT-IR spectro-
scopy techniques and compared with the authentic samples.
2. Experimental
2.1. Instruments and characterization
The catalyst was characterized by X-ray diffraction (Bruker
D8ADVANCE, Cu Ka radiation), FT-IR spectroscopy (Nicolet 400D
in KBr matrix in the range of 4000–400 cmꢀ1), BET specific
surface areas and BJH pore size distribution (Series BEL SORP
18, at 77 K), thermal analyzer TGA (Setaram Labsys TG (STA) in
temperature 30–700 1C and heating rate of 10 1C/min in N2
atmosphere) and SEM (Philips, XL30, SE detector).
The products were characterized by 1H and 13C NMR spectra
(Bruker DRX-500 Avance spectrometer at 500.13 and 125.47 MHz,
respectively), GC (Agilent 6820 equipped with a FID detector) and
GC–MS (Agilent 6890). Melting points were measured on an
Electrothermal 9100 apparatus and they were uncorrected. All
the products were known compounds and they were character-
ized by FTIR, 1H NMR and 13C NMR. All melting points were
compared satisfactorily with those reported in the literature.
3. Results and discussion
3.1. Characterization of the catalyst
3.1.1. X-ray diffraction analysis
Fig. 1 depicts the powder X-ray diffraction patterns of the
solids SiO2–Al2O3 (a) and P4MVPH–SiO2–Al2O3 (in-situ) (b). The
solid SiO2–Al2O3 displays the characteristic spectral profile of an
amorphous aluminosilicate with an amorphous halo present in
2.2. Catalyst preparation
the 2
y¼23 [40]. This typical halo results from the dispersion
2.2.1. Preparation of the 4-methyl vinyl pyridinium hydroxide–
SiO2–Al2O3 composite by in-situ polymerization
of the angles and bond distances between the basic structural
units (silicates and aluminates) which destroys the structure
periodicity and produces a non-crystalline material. No changes
in the diffraction patterns are observed of P4MVPH–SiO2–Al2O3
(Fig. 1b), thus reinforcing the assumption that P4MVPH hybridi-
zation occurs on the solid surface without changing the structural
form of the SiO2–Al2O3.
In the first step, poly 4-vinyl pyridine–SiO2–Al2O3 was prepared
by in-situ method. Aluminum isopropoxide (1.84 g, 9 mmol) was
dissolved in n-butanol. Through this clear solution, acetyl acetone
(2.06 mL, 0.02 mol), TEOS (2 mL, 8.9 mmol), 4-vinylpyridine (2 mL,
18.5 mmol) and K2S2O8 (0.5 g, 1.84 mmol) were added under
continuous stirring, and the mixture was heated to 60–70 1C. After
1 h, the solution was cooled down to room temperature and
deionized water (10 mL) as the hydrolyzing agent was added
slowly. The reaction mixture was left overnight to hydrolyze
the alkoxides, yielding transparent gel. The obtained gel was
dried at 60 1C and gave 4.2 g poly 4-vinyl pyridine–SiO2–Al2O3
(P4VP–SiO2–Al2O3).
In the second step, the obtained P4VP–SiO2–Al2O3 (4.2 g), CH3I
(2 mL, 0.046 mol) and CH2Cl2 (20 mL) were added to a 50 mL
round-bottomed flask. The solution was stirred with magnetic
stirrer and refluxed for 6 h at 40 1C. This mixture was filtered and
washed with CH2Cl2 (2 ꢁ 10 mL) and the precipitate was dried in
air to yield poly 4-methyl vinyl pyridinium iodide–SiO2–Al2O3
(P4MVPI–SiO2–Al2O3).
3.1.2. FTIR analysis
Fig. 2 presents the FTIR spectra of SiO2–Al2O3 (a), P4VP (b),
P4VP–SiO2–Al2O3 (c), P4MVPI–SiO2–Al2O3 (d) and P4MVPH–SiO2–
Al2O3 (e). In the case of solid SiO2–Al2O3, the bands expected for
the aluminosilicate can be observed in the 1050 cmꢀ1 (Si–O bond
stretching) and 460 cmꢀ1 (Al–O bond stretching) regions [41],
which are seen in Fig. 1a,c,d,e. The other absorption peak of Al–O
stretching vibration in the range of 1000–1200 cmꢀ1 could not be
resolved due to its overlap with the absorption peak of Si–O–Si
stretching vibration in the range of 1000–1200 cmꢀ1. There is also
a band in 3429 and 1632 cmꢀ1 due to the O–H bonds vibration.
In the FT-IR spectrum of P4VP–SiO2–Al2O3 (Fig. 1c), the new
bands at 1598, 1558, 1496 and 1406 cmꢀ1 were the characteristic
absorptions of pyridine ring. Among them, the band which
appeared at 1598 cmꢀ1 was the stretching vibration absorption
of C–N bond and the bands at 1558, 1496 and 1406 cmꢀ1 were
In the third step, the aqueous solution of NaOH (0.027 mol of
NaOH in 20 mL ꢂ H2O) was added to the obtained P4MVPI–SiO2–
Al2O3 at room temperature. The mixture was stirred for 7.5 h.
Then, it was filtered and washed sequentially with deionized

R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
2011
o
3
7 3
8
2
2
o
o
2
2
2
3
2
3
2
2
3
2
2
2
3
2
3
2
2
2
3
2
2
3
2
2
3
2
2
3
Scheme 1. Preparation of P4MVPH–SiO2–Al2O3.
P4VP–SiO2–Al2O3. These were consistent with the spectrum of
P4VP (Fig. 1b).
The appearance of the above bands shows that P4VP has been
attached on the surface of SiO2–Al2O3 and the P4VP–SiO2–Al2O3
composite is obtained. In the spectra of P4MVPI–SiO2–Al2O3
and P4MVPH–SiO2–Al2O3 (Fig. 1d, e), a new peak appears at
1643 cmꢀ1 which is ascribed to the C–N (CH3–pyridinium) bond
absorption. This observation confirms the N-alkylation of pyridine
ring. In the FT-IR spectrum of P4MVPH–SiO2–Al2O3 (Fig. 1e), the
peak at 3450 cmꢀ1 is stronger than in the other spectra, in which
the stretching vibration of OH groups is shown. Furthermore, OH
bending characteristic at 1643 cmꢀ1 is seen. The appearance
of these bands suggests that the exchange between OHꢀ and Iꢀ
groups on P4MVPI–SiO2–Al2O3 occurred and the modified parti-
cles P4MVPH–SiO2–Al2O3 were formed.
3.1.3. BET surface area and pore size analysis
The N2 adsorption-desorption isotherms and the pore-size dis-
tributions of pure SiO2–Al2O3 (a) and P4MVPH–SiO2–Al2O3 (in-situ)
(b) samples are shown in Fig. 3. The isotherms are similar to Type III
isotherm with H1-type hysteresis loops at high relative pressure
according to the IUPAC classification, characteristic of amorphous
and microporous materials. The specific surface area and the pore
size have been calculated using Brunauer–Emmett–Teller (BET) and
Barrett–Joyner–Halenda (BJH) methods, respectively.
Fig. 1. The powder XRD pattern of the solids (a) SiO2–Al2O3 and (b) P4MVPH–
SiO2–Al2O3 (in-situ).
attributed to the stretching vibration absorption of C¼C bond.
Moreover, the presence of peaks at around 2800–3050 cmꢀ1
corresponded to the aromatic and aliphatic C–H stretching in
The structure data of all these materials (BET surface area, total
pore volume, and pore size) are summarized in Table 1. It is
known that SiO2–Al2O3 has a high BET surface area (178 m2/g),

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R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
Fig. 3. The N2 adsorption-desorption isotherm of pure (a) SiO2–Al2O3 and (b)
P4MVPH–SiO2–Al2O3 (in-situ) and pore-size distributions of (c) SiO2–Al2O3 and (d)
P4MVPH–SiO2–Al2O3 (in-situ).
Table 1
Porosity data of SiO2–Al2O3 and P4MVPH–SiO2–Al2O3 samples.
Sample
BET surface
area (m2 gꢀ1
Pore volume
(cm3 gꢀ1
)
Pore size
(nm)
)
SiO2–Al2O3
178.0
89.3
1.5
0.6
33.6
27.0
P4MVPH–SiO2–Al2O3
Fig. 4. TGA curves of (a,b) P4MVPH–SiO2–Al2O3 (in-situ).
pores of SiO2–Al2O3 or could be well-dispersed in inner pore
resulting in a decrease in surface area and average pore diameter
(Fig. 3d). However, for the catalyst prepared by in-situ method,
the polymer chains are entangled like skeins in the structure of
SiO2–Al2O3, and lead to increase the contact surface.
Fig. 2. FT-IR spectra of (a) SiO2–Al2O3, (b) P4VP, (c) P4VP–SiO2–Al2O3,
(d) P4MVPI–SiO2–Al2O3 and (e) P4MVPH–SiO2–Al2O3.
a large pore volume (1.49 cm3/g) and a pore size (33.64 nm),
indicative of its potential application as a host in organic materi-
als. Also, Table 1 shows that after hybridization with P4MVPH
through in-situ polymerization, textural properties of composite
are smaller than SiO2–Al2O3 support.
3.1.4. Thermal property
The thermogravimetric analysis (TG and DTG) curve of the
P4MVPH–SiO2–Al2O3 has been investigated. The P4MVPH–SiO2–
Al2O3 (in-situ) sample (Fig. 4) shows two separate weight loss
The pore size distribution patterns shown in Fig. 3c,d, reveal
that the homogeneous distribution of polymer could block small

R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
2013
steps. The first step (around 13%, w/w) appearing at temperature
o150 1C corresponded to desorption of physically adsorbed
water (i.e., adsorbed water on the inner and outer surface). The
second weight loss (about 150–700 1C) which amounts to around
17% (w/w) is related to the decomposition of the polymer moiety.
carbanion intermediate to the carbonyl group. Finally, elimination
of the hydroxyl group occurs to form a C¼C bond and water,
while the basic site (hydroxide ion) is restored. Plausible mechan-
ism of the Knoevenagel reaction over P4MVPH–SiO2–Al2O3 is
denoted in Scheme 2.
The effects of some parameters on Knoevenagel condensations
of benzaldehyde with malononitrile were investigated, and the
results are as follows:
3.1.5. Scanning electron microscopy (SEM)
Fig. 5 gives the scanning electron microscopy (SEM) photo-
graphs of SiO2–Al2O3 (a,c) and P4MVPH–SiO2–Al2O3 (in-situ) (b,d)
samples.
The effect of the amount of catalyst on the Knoevenagel
condensation reaction was investigated using 1 mmol of benzal-
dehyde and 1 mmol of malononitrile at room temperature and in
solvent-free conditions. The values are shown in Table 2. The
results showed that by increasing the amount of catalyst from
0.06 to 0.12 g, the reaction completion time decreased. When
0.12 g of the catalyst was employed, the reaction was completed
in less than 3 min at room temperature. Moreover, with an
increase or a decrease in the catalyst amount, the selectivity
was constant.
The effect of the amount of 4-vinyl pyridine (4VP) on the yield
of the reaction was studied by varying the amount of monomer,
where the other parameters were kept constant (Table 3). By
increasing the amount of monomer to 2 mL (the amounts of
aluminum isopropoxide and TEOS were kept constant according
to the experimental section), the yield increased because of the
increase in the basic active catalyst sites. With further increase in
monomer amount from 2 to 3 mL, the completion time increased,
which can be due to aggregation of the polymers.
In order to investigate the effect of SiO2–Al2O3 on the catalytic
activity, in the absence of P4MVPH, SiO2–Al2O3 was used as the
catalyst for the Knoevenagel reaction and after 30 min, yield was
7% (Table 3). However, the yield of the Knoevenagel reaction over
P4MVPH–SiO2–Al2O3 was 98% in 3 min (in the modified condi-
tions). As we showed in the plausible mechanism (Scheme 2), the
hydroxide ions are the active sites of the catalyst. These active
sites do not exist in the SiO2–Al2O3 and the basic sites in
P4MVPH–SiO2–Al2O3 are more active than SiO2–Al2O3. Thus the
higher activity of P4MVPH–SiO2–Al2O3 in the Knoevenagel
reaction was not attributed to the higher surface area (Table 1),
and it should be related to the nature of the active basic sites. Also
comparative reaction by using P4MVPH and P4MVPH–SiO2–Al2O3
In the SEM photograph of SiO2–Al2O3, it can be seen that the
mixed-oxide surface is uniform and is like a sponge (Fig. 5a,c). On
the other hand, Fig. 5b,d shows a different morphology. The
SEM photograph of P4MVPH–SiO2–Al2O3 (in-situ) shows regular
distribution of P4MVPH in the structure of SiO2–Al2O3. It can be
seen that P4MVPH is completely mixed with SiO2–Al2O3 particles
and the composite is uniform. It is obvious that before hybridiza-
tion, the surface of SiO2–Al2O3 is somewhat smooth, whereas
after hybridization, the surface of composite becomes coarser. In
addition, it can be seen that the particle size in the P4MVPH–
SiO2–Al2O3 is much lower than that of SiO2–Al2O3 (Fig. 5c,d).
3.2. Catalytic activity
This novel composite was synthesized and fully characterized
with different methods. The main goal of this catalytic synthesis
was to compare this organic–inorganic composite with other
functional polymeric materials and to expand the use of these
types of composites for organic reactions. This composite was
prepared by a very simple and inexpensive method without using
any bridged organosilanes compound (the bridged organosilanes
precursors either involve complicated synthesis and purification
method or are very expensive). In order to investigate the basic
properties of this catalyst, the Knoevenagel condensation was
chosen as a typical reaction.
The accepted mechanism for the base-catalyzed Knoevenagel
condensation involves a first step in which the formation of
the carbanion on the methylenic group occurs by abstraction of
the proton by the basic catalyst. This is followed by attack of the
Fig. 5. Scanning electron microscopy (SEM) photographs of (a,c) SiO2–Al2O3 and (b,d) P4MVPH–SiO2–Al2O3 (in-situ).

2014
R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
OH
N
CH3
CN
CN
CN
CN
OH
H2C
N
N
CH3
+
OH
CH3
P4MVPH-SiO2-Al2O3
CN
CH
CN
CN
CN
CN
O
H
HO
H
C
C
C
CH C
CN
O
CN
CN
H2O
-H2O
H
C
+
H
OH
Scheme 2. Plausible mechanism of the Knoevenagel reaction over P4MVPH–SiO2–Al2O3.
Table 2
Effect of the amount of catalysta.
Table 4
Reusability of the catalysta.
Amount of catalyst (g)
Time (min)
Yield (%)b
Cycle
Time (min)
Yield (%)b
0.06
0.08
0.1
3
8
3
6
3
4
3
45
98
50
98
85
98
98
Fresh
1
3
3
4
3
5
3
6
3
8
3
9
98
95
98
85
98
60
98
45
98
40
98
2
3
4
5
0.12
a
Reaction conditions: benzaldehyde (1 mmol), malo-
nonitrile (1 mmol), catalyst (0.12 g, P4MVPH–SiO2–Al2O3),
solvent-free, room temperature.
b
Isolated yield.
a
Reaction conditions: benzaldehyde (1 mmol), malo-
nonitrile (1 mmol), catalyst (0.12 g, P4MVPH–SiO2–Al2O3),
solvent-free, room temperature.
Table 3
b
Isolated yield.
a
Effect of 4-VP amount on catalytic activity of P4MVPH–SiO2–Al2O3
.
Amount of 4-VP (mL)b Time (min) Yield (%)c Amount of basic sites
of the catalyst (mmol gꢀ1
area on whose surfaces polymer chains can be distributed uni-
formly. In this condition, the quternized pyridine rings that are
the original centers for doing the reaction, are free and it is
possible for the reactant to reach the active sites of the catalyst
(hydroxide ions). So, we can conclude that the yield of the
reaction was high on the surface of P4MVPH–SiO2–Al2O3. On
the other hand, in the P4MVPH there are many interactions
between the chains of the polymers and some of the pyridine
ring trapped in the chains of the polymer. So, there is hindrance
around the pyridine rings that can prevent the reactant to reach
the active sites of the catalyst (hydroxide ions). This can reduce
the activity of the P4MVPH. Therefore, it can be said that the
existence of both organic and inorganic phases has critical effects
on the catalytic activity of the catalyst.
)
–
1
30
3
7
60
98
98
80
98
–
2.6
7
2
3
3
4.8
5.6
3
5
a
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1 mmol),
catalyst (0.12 g, P4MVPH–SiO2–Al2O3), solvent-free, room temperature.
b
The amounts of Aluminum isopropoxide and TEOS were kept constant
according to the experimental section.
c
Isolated yield.
showed that P4MVPH–SiO2–Al2O3was more efficient, by comple-
tion the reaction in a short time. On the other hand, the yield was
decreased and the reaction was carried out in a long period of
time using P4MVPH (81% yield after 20 min).
It should be mentioned that one of the greatest advantages of
this catalyst was to easily use due to its powdery structure.
P4MVPH was adhesive and this character made it hard to separate
it from the vessel; but after in-situ hybridization with SiO2–Al2O3
and making P4MVPH–SiO2–Al2O3 composite, it becomes powdery
which was easily used and recycled. SiO2–Al2O3 has high surface
The reusability of the catalyst was studied by using P4MVPH–
SiO2–Al2O3 in recycling experiments (Table 4). In order to regen-
erate the catalyst, after the completion of the reaction, it was
separated by filtration, washed several times with deionized
water, dried at 60 1C and used in the reaction with a fresh
reaction mixture. The catalyst was reused up to 5 times without
any significant loss of its catalyst activity, and the selectivity was
constant (100%).
The P4MVPH–SiO2–Al2O3 catalyst also showed good activity
and selectivity in the Knoevenagel condensation reaction using

R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
2015
Table 5
Knoevenagel condensation of various aldehydes and malononitrile catalyzed by P4MVPH–SiO2–Al2O3
a
:
b
Entry
Substrate
Product
Time (min)
Yield (%)
Mp (deg.)
Found
Ref.
Reported
1
2c
3
3
98
98
98
98
98
98
81–83
81–83
82–84
[42,46,47]
[42,43,47]
[43]
8
82–84
15
24
28
40
182–183
182–183
160–162
160–162
180–182
180–182
159–161
159–161
4c
[43]
5
[42,43,47]
[42,43,47]
6c
7
8
20
15
98
98
96–98
95–96
[45,47]
[48]
114–118
116–117
9
16
28
24
98
98
98
153–154
153–154
167–168
153–155
153–155
168–169
[44]
[44]
10c
11
[42,43,47]
12
13
14
30
27
5
98
98
98
175–179
132–134
102–104
178–180
133–135
103–104
[47]
[31]
[47]
15
16
90
55
91
98
Liquid
Liquid
–
–
[31]
[31]

2016
R.J. Kalbasi et al. / Journal of Solid State Chemistry 184 (2011) 2009–2016
Table 5 (continued )
b
Entry
Substrate
Product
Time (min)
Yield (%)
Mp (deg.)
Found
Ref.
Reported
17
a
40
98
Liquid
–
[32]
Reaction conditions: aldehyde (1 mmol), malononitrile (1 mmol), catalyst (0.12 g, P4MVPH–SiO2–Al2O3), solvent-free, room temperature.
b
c
Isolated yield.
Catalyst (0.06 g, P4MVPH–SiO2–Al2O3).
different kinds of aromatic and aliphatic aldehydes [42–48]. The
results are given in Table 5. In all cases, selectivity for carbonyl
compound was 100%.
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catalyst for the Knoevenagel condensation reaction of various
aldehydes with malononitrile with 100% selectivity to
a,b-unsa-
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chemo-selectivity. The reactions occur at room temperature and
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