Comparative study on the catalytic properties of amino-functionalized silica materials for the transesterification of dimethyl oxalate with phenol

Article abstract of DOI:10.1590/S0103-50532010001200012

A series of hybrid mesoporous MCM-41 materials containing different amino groups (such as 3-aminopropyl (AP-), (2-aminoethylamino)propyl (AAP-), or [2-(2-aminoethylamino)ethylamino] propyl (AEP-) group) were prepared by a post-grafting method, and characterized by means of X-ray powder diffraction (XRD), N2 adsorption, Fourier transform-infrared spectroscopy (FT-IR) and temperature-programmed desorption of CO₂ (CO₂-TPD). The catalytic properties of these hybrid materials were investigated for the transesterification of dimethyl oxalate with phenol. All the samples were active for the transesterification. Among them, the sample AEP-MCM-41 exhibited the highest activity under test conditions. And only a slight decrease in activity could be observed after few runs, indicating the good recyclability of this catalyst. Notably, the activity of the used catalyst could be regenerated by simple treatment with diluted basic agents under mild conditions. Moreover, effects of the density and the basic strength of the amino groups on the catalytic properties were taken into consideration for understanding the reaction mechanism and the possible formation route of the by-product anisole.

Full text of DOI:10.1590/S0103-50532010001200012

J. Braz. Chem. Soc., Vol. 21, No. 12, 2254-2261, 2010.
Printed in Brazil - ©2010 Sociedade Brasileira de Química
0
103 - 5053 $6.00+0.00
Comparative Study on the Catalytic Properties of Amino-Functionalized Silica
Materials for the Transesterification of Dimethyl Oxalate with Phenol
a
b
a
a
a
Yan Liu, Guoming Zhao, Wanchun Zhu, Jing Wang, Gang Liu,
a
,a
Wenxiang Zhang and Mingjun Jia*
a
State Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry,
Jilin University, Changchun, 130021, China
b
Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology,
Chinese Academy of Sciences, Qingdao, 266101, China
Uma série de materiais híbridos mesoporos MCM-41, contendo diferentes grupos amino
(
como 3-aminopropila (AP-), (2-aminoetilamino)propila (AAP-), ou [2-(2-aminoetilamino)
etilamino]propila (AEP-)) foi preparada pelo método de pós-enxertia e caracterizada por difração
de raio X de pó (XRD), adsorção de N , espectroscopia de infravermelho com transformada de
2
Fourier (FT-IR) e dessorção de CO com temperatura controlada (CO -TPD). As propriedades
2
2
catalíticas destes materiais híbridos para a reação de transesterificação de dimetil oxalato com
fenol foram investigadas. Verificou-se que todos são ativos, particularmente o AEP-MCM-41,
que apresentou a maior atividade dentre eles. Apenas um pequeno decréscimo na atividade
foi observado após vários ensaios catalíticos sucessivos utilizando o mesmo catalisador,
indicando uma boa reciclabilidade do mesmo. Notavelmente, a atividade do catalisador pode ser
regenerado por simples tratamento com base, sob condições brandas. Além disso, os efeitos da
densidade e da força básica dos grupos amino sobre as propriedades catalíticas foram exploradas
na proposição do mecanismo de reação, incluindo a provável rota que leva à formação do
subproduto anisol.
A series of hybrid mesoporous MCM-41 materials containing different amino groups (such as
3-aminopropyl (AP-), (2-aminoethylamino)propyl (AAP-), or [2-(2-aminoethylamino)ethylamino]
propyl (AEP-) group) were prepared by a post-grafting method, and characterized by means of
X-ray powder diffraction (XRD), N adsorption, Fourier transform-infrared spectroscopy (FT-IR)
2
and temperature-programmed desorption of CO (CO -TPD). The catalytic properties of these
2
2
hybrid materials were investigated for the transesterification of dimethyl oxalate with phenol.
All the samples were active for the transesterification. Among them, the sample AEP-MCM-41
exhibited the highest activity under test conditions. And only a slight decrease in activity could be
observed after few runs, indicating the good recyclability of this catalyst. Notably, the activity of
the used catalyst could be regenerated by simple treatment with diluted basic agents under mild
conditions. Moreover, effects of the density and the basic strength of the amino groups on the
catalytic properties were taken into consideration for understanding the reaction mechanism and
the possible formation route of the by-product anisole.
Keywords: amino-functionalized, MCM-41, dimethyl oxalate, transesterification, recyclability
Introduction
due to excellent mechanical, optical, electrical and heat-
1,2
resistance properties. So far, various approaches for DPC
synthesis have been reported, including phosgene route,
oxidative carbonylation of phenol and transesterification
Diphenyl carbonate (DPC) is an industrially important
intermediate for the production of several organic
chemicals, especially as the precursor for the synthesis of
polycarbonates (PCs), which have been used in many fields
1
,3-19
reaction.
Among them, transesterification of dimethyl
oxalate (DMO) with phenol to diphenyl oxalate (DPO),
following a decarbonylation reaction, is an attractive and
13-19
*
e-mail: jiamj@jlu.edu.cn
environmentally friendly route for the synthesis of DPC.

Vol. 21, No. 12, 2010
Liu et al.
2255
It was reported that some homogeneous Lewis acid
catalysts and soluble organic metal compounds were
active for the transesterification of DMO with phenol.
Experimental
1
3,14
Preparation of amino-functionalized materials
However, from an industrial point of view, the difficulty of
separating catalysts from products in a homogeneous system
and the potential environmental impact must be considered.
Based on these concerns, heterogeneous catalysis is
receiving more attention, and it was reported that a variety
of metal oxides bearing weak acidity were effective for
the transesterification of DMO with phenol, including
Ti-containing phosphate catalysts, MoO /TiO -SiO ,
The amino-functionalized mesoporous MCM-41
materials were prepared by a post-grafting method.
3
8
Three types of organosilanes containing different number
of amino groups were used: 3-aminopropyltriethoxysilane
(APTES), which contains just one amino group in
each molecule, [3-(2-aminoethylamino)propyl]
trimethoxysilane, (AAPTMS), which contains two
amino groups, 3-[2-(2-aminoethylamino)ethylamino]
propyltrimethoxysilane (AEPTMS), which contains three
amino groups. Typically, the support of MCM-41 (1.0 g),
3
2
2
15-19
TiO /SiO and metal modified zeolites.
2
2
Recently, the heterogenization of organic bases has
become an interesting subject owing to a variety of basic
compounds showing unusual performance for different
3
9
prepared following a literature procedure, was pre-
activated by heating to 423 K under vacuum for 3 h. After
cooling and release of the vacuum, dry toluene (30 mL)
and a certain amount of organosilane was added under
20-37
catalytic reactions.
For example, amino-functionalized
mesoporous materials have attracted much attention for
their wide applications in Knoevenagel condensation,
aldol reaction, nitroaldol reaction, Michael additions, and
N atmosphere, and the mixture was refluxed for 12 h.
2
27-33
epoxide ring-opening reactions.
Notably, it was reported
Finally, the resulting solid was filtered, washed, Soxhlet-
extracted with dichloromethane for 24 h, and dried under
vacuum at 333 K. The obtained materials were denoted
as AP-MCM-41, AAP-MCM-41 and AEP-MCM-41,
respectively. In general, the loading of amino group on the
that some amino-functionalized materials were efficient
catalysts for the transesterification reactions of esters (i.e.,
ethylene carbonate, diethylmalonate and β-ketoester) with
3
4-37
alcohols.
-1
During the past few years, our group has also carried out
some work on developing novel heterogeneous catalysts
three hybrid materials is 0.75 mmol g (the corresponding
amount of organosilane is as follows: APTES 0.83 mmol,
AAPTMS 0.85 mmol, AEPTMS 0.89 mmol). The AEP-
MCM-41 samples with different loading ofAEP group are
denoted as xAEP-MCM-41 (x is the loading ofAEP, which
1
5,18,38
for the transesterification of phenol with DMO,
and we just reported recently that cyclopentadienyl-
functionalized mesoporous MCM-41 materials bearing
3
8
-1
weak basic sites were active catalysts for this reaction. In
the continuation of this work, several hybrid mesoporous
MCM-41 materials containing different amino groups
is 0.50, 0.75 or 1.02 mmol g , and the corresponding amount
of AEPTMS is 0.56, 0.89 or 1.25 mmol, respectively.).
(
such as 3-aminopropyl (AP-), (2-aminoethylamino)
Catalyst characterization
propyl (AAP-), or [2-(2-aminoethylamino)ethylamino]
propyl (AEP-) group) were prepared by a post-grafting
method, and their catalytic properties were investigated
for the transesterification of DMO with phenol in the
Powder XRD patterns were recorded on a Shimadzu
XRD-6000 diffractometer (40 kV, 30 mA) using
Ni-filtered CuKα radiation (λ = 0.15418 nm). N2
adsorption-desorption isotherms were measured at 77 K
using a Micromeritics ASAP 2010N analyzer. Samples
were degassed at 423 K for 8 h before measurements.
Specific surface areas were calculated using the BET
model. The N content was estimated by Perkin-Elmer 2400
CHN analyzer.
3
1
present work. Previously, Suzuki et al. reported that
hybrid mesoporous silica spheres containing the above
amino groups, prepared by co-condensation method,
showed excellent catalytic activities in the nitroaldol
condensation reactions. Here, we found that the grafted
MCM-41 materials containing these amino groups were
active and recyclable catalysts for the transesterification
of DMO with phenol, and the activity of the used catalyst
could be easily recovered by simple treatment with diluted
basic agents under a mild condition. Moreover, effects of
the density and the basic strength of the amino groups on
the catalytic properties were discussed, and a possible
route for the formation of anisole as by-product was also
proposed.
FT-IR spectra were obtained using a Nicolet Impact
410 spectrometer. All materials have been dehydrated at
423 K for 5 h prior to spectrum collection. The spectra
were recorded using KBr wafers containing 2% of the dried
-
1
sample at ambient conditions with a resolution of 4 cm
and 32 scans in the region from 400 to 4000 cm .
-1
TPD experiments were carried out using CO as
2
probe molecules. Typically, 50 mg of fresh samples were

2
256
Comparative Study on the Catalytic Properties of Amino-Functionalized Silica Materials
J. Braz. Chem. Soc.
pretreated at 423 K under Ar stream for 1 h, then cooled
framework and organic groups which are located inside the
pore channels of the mesoporous materials.
4
1,42
to 303 K. CO was injected into the stream until saturation
2
was reached, and the system was maintained at 303 K for
The successful introduction of organic groups into
the mesoporous support could be further confirmed by
the FT-IR characterization. Typical bands associated with
the formation of a condensed silica network are present
in all cases (Si–O–Si bands around 1222, 1080, 804 and
1
3
h. After purging the system with flowing Ar for 1 h at
03 K, the samples were heated at the rate of 10 K min ,
-1
and the amount of desorbed CO monitored using an online
2
thermal conductivity detector (TCD).
-1
-1
4
60 cm ). The broad band between 3300 and 3600 cm
Catalytic reaction
corresponds to the stretching mode of N–H, which are
4
3
cross-linked with surface silanol (Si–OH) groups. The
-1
The catalytic reaction was carried out in a 250 mL
three-neck flask equipped with a thermometer, a distillation
apparatus, and a stirrer under refluxing condition at
peak around 1636 cm mainly arises from N–H bending
mode, which is overlapped with the bending vibrational
3
2,40,43
modes of adsorbed H O.
The bands in the region
2
-1
1
5,38
atmospheric pressure.
The reaction temperature was
from 2800 to 3000 cm can be ascribed to the stretching
vibrational mode of –CH groups in aminosilanes.
3
2,40,44
kept at 453 K. The reactants and products were analyzed
by gas chromatograph (Shimadzu GC-8A equipped with
a HP-5 capillary column) using ethyl benzoate as internal
standard. DPO, MPO and the by-product anisole from the
transerterification reaction were quantified by comparing
the peak areas with their corresponding standards. In all
tests, carbon balances were within 100 ± 5%.
Reusability tests were conducted with a used catalyst
from a typical experiment after recovery of the solid by
filtration, washing with acetone and drying under vacuum at
2
N adsorption-desorption isotherms show that all the
2
samples satisfy the type IV hysteresis loop in accordance
4
5
with IUPAC classification, which is characteristic of
mesoporous materials possessing pore sizes between 2
and 50 nm. And the uniformity of the curves shows that
the integrity of the mesoporous structure of MCM-41 is
preservedafter the introductionof organic groups. Compared
with the original support, obvious decrease in surface area,
pore volume, and pore size was observed for the amino-
functionalized MCM-41 materials (as shown in Table 1),
343 K. In addition, the regeneration of the used catalyst was
-1
41
carried out by treating the catalyst with 0.2 mol L methanol
solution of tetramethylamonium hydroxide (TMAOH) and
thoroughly washing with methanol in a Soxhlet apparatus
in order to remove the trace amount of TMAOH adsorbed
on the surface of the catalyst.
Results and Discussion
Catalyst characterization
which can be assigned to the introduction of amino groups.
40
According to the XRD characterization results, it
was known that all the amino-functionalized materials
display the hexagonally ordered MCM-41-type structure,
indicating that the inorganic wall structure of the MCM-41
silica remains intact after functionalization. For the hybrid
materials, the reduction in diffraction intensity might
be mainly due to contrast matching between the silicate
Figure1.CO -TPDprofilesof(a)0.75AP-MCM-41,(b)0.75AAP-MCM-41,
(c) 0.75AEP-MCM-41and (d) parent MCM-41.
2
Table 1. The structure parameters of several amino-functionalized silica materials
2
-1
3
-1
a
Samples
BET surface area / (m g )
Pore vol. / (cm g )
Pore size / nm
MCM-41
1429
962
952
953
1.44
0.90
0.87
0.94
3.21
2.91
2.76
2.96
0
0
.75AP-MCM-41
.75AAP-MCM-41
.75AEP-MCM-41
0
a
Calculated by using the BJH model on the adsorption branch of the isotherms.

Vol. 21, No. 12, 2010
Liu et al.
2257
The basicity of amino-functionalized MCM-41
These results suggest that the anchored amino groups are
the main active sites of these functionalized catalysts, and
the mesoporous support may also play a role in improving
the catalytic activity of the hybrid materials.
materials was determined on the basis of the CO -TPD
2
profiles (as shown in Figure 1). MCM-41 support showed
two peaks in the range from 325 to 400 K which can be
4
6
mainly attributed to the desorption of physisorbed CO2.
ForAP-MCM-41, an additional desorption peak appeared at
75 K, which should be due to the chemisorbed CO on the
According to the CO -TPD results, it was known that
2
AEP-MCM-41 bears a stronger basicity than either AP-
MCM-41 or AAP-MCM-41. Moreover, it was also known
4
2
47
moderate basic sites (i.e., amino group). With the increase
that the basicity of the primary amine (-NH ) is higher,
2
of the length of alkyl chain and the number of amino groups,
and the steric hindrance of this primary amine is smaller
than of other amino groups (-NH-) present in the same
organosilane molecule. Hence, we propose that the primary
amine should be the main active sites of AEP-MCM-41
material, and the relatively high activity of AEP-MCM-41
may be assigned to its relatively strong basicity. Besides,
the chemical and structural features of the support may
also affect the catalytic properties. We suppose that the
solid support can improve the degree of site-isolation
of organosilane groups and thus enhancing the catalytic
activity and selectivity to the main products.
the desorption peak of chemisorbed CO shifted to higher
2
temperature, indicating that the basic strength of different
amino-functionalized materials increases in the order:
AP-MCM-41 < AAP-MCM-41 < AEP-MCM-41.
Catalytic properties in transesterification of DMO with
phenol
The catalytic properties of the amino-functionalized
materials are shown in Table 2. Very low conversion
of DMO could be observed in the blank reaction (no
catalyst). Under such reaction conditions, the activity
of parent MCM-41 silica was low, and it showed 18.6%
conversion of DMO and very low yield of DPO (1.0%)
after 10 h of reaction. The homogeneous catalyst
In addition, the reusability of the amino-functionalized
mesoporous silica was examined over AEP-MCM-41
catalyst (Table 3). It was found that the activity decreased
slightly in the second run, and the conversion of DMO
remained constant in the subsequent runs (entries 1-4).
Here, the difference in activity between the fresh catalyst
and the used one might be partially attributed to the
adsorption of a certain amount of DMO to the catalyst.
Furthermore, the TMAOH treated catalyst showed a 79.8%
conversion of DMO with 31.0% selectivity of DPO (see
Table 3, entry 5), indicating that most of the active sites
could be regenerated by such simple basic treatment.
Previously, by investigating the catalytic properties of
aminopropyl-functionalized material for the nitroaldol
(
AEPTMS) was active for the reaction, and it gave 55.5%
conversion of DMO and 5.0% yield of DPO after 10 h
entry 6). Comparatively, various amino-functionalized
(
materials exhibited relatively high catalytic activity and
DPO yield. In the case of AP-MCM-41, which possesses
just one amino group in each organosilane, it gave 55.0%
conversion of DMO, with 7.4% yield of DPO after 10 h.
Under the same reaction conditions, AAP-MCM-41,
which has two amino groups, gave 71.0% conversion
of DMO and 13.2% yield of DPO. As for the sample
of AEP-MCM-41, which contains three amino groups,
it exhibited the highest activity (80.9% conversion of
DMO and 21.5% yield of DPO), among the analogous
homogeneous catalysts as well as the hybrid materials.
4
0
reaction of aldehyde with nitroalkane, Zhang et al.
4
8
and Sartori et al. reported that the deactivated catalyst
could be regenerated by the treatment with propylamine
-
1
(10% v/v ethanol solution) or TMAOH (0.2 mol L
methanol solution). They suggested that the deactivation
a
Table 2. The catalytic properties of amino-functionalized silica catalysts for transesterification of phenol with DMO
Entry
Catalysts
Conversion of
DMO / (%)
Selectivity / (%)
Yield / (%)
MPO
91.0
88.1
84.4
67.4
59.6
75.8
DPO
2.7
anisole
1.9
MPO
5.8
DPO
0.2
1
2
3
4
5
no catalyst
MCM-41
6.4
18.6
55.0
71.0
80.9
55.5
5.4
3.0
16.4
46.4
47.9
48.2
42.1
1.0
0.75AP-MCM-41
0.75AAP-MCM-41
0.75AEP-MCM-41
AEPTMS
13.4
18.6
26.6
9.0
2.2
7.4
14.1
13.7
15.2
13.2
21.5
5.0
6
a
Reaction conditions: catalyst 1.8 g (or 1.35 mmol AEPTMS), phenol 0.5 mol, phenol/DMO = 5.0, reaction time 10 h , reaction temperature 453 K. MPO:
methyl phenyl oxalate.

2
258
Comparative Study on the Catalytic Properties of Amino-Functionalized Silica Materials
J. Braz. Chem. Soc.
a
Table 3. The stability of 0.75AEP-MCM-41 for transesterification of phenol with DMO
Entry
Run
Conversion of
DMO / (%)
Selectivity / (%)
Yield / (%)
MPO
59.6
74.5
78.8
77.1
66.9
DPO
26.6
14.2
15.5
17.6
31.0
anisole
13.7
11.1
5.7
MPO
48.2
46.5
51.5
48.2
53.4
DPO
21.5
8.9
1
2
3
4
1
2
3
4
5
80.9
62.4
65.4
62.4
79.8
10.1
11.0
24.7
5.3
b
5
2.1
a
b
Reaction conditions: catalyst 1.8 g, phenol 0.5 mol, phenol/DMO = 5.0, reaction time 10 h, reaction temperature 453 K. MPO: methyl phenyl oxalate. Before
th
-1
the 5 running, the used catalyst was treated with 0.2 mol L methanol solution of TMAOH, Soxhlet-extracted with methanol and dried under vacuum.
of the catalyst turned from white to yellow after the first
run, and a possible explanation could be the adsorption of
organic molecules on the active sites during the reaction.
Thus, we speculate here that the main reason for the
decrease of the catalytic activity could be assigned to the
adsorption of reactants and products on the surface of the
hybrid catalysts. Notably, the intensity of those additional
bands, which are assigned to the adsorption of organic
molecules, decreased considerably after the used catalyst
-1
was treated with 0.2 mol L methanol solution of TMAOH
see Figure 2c), which means that most of the adsorbed
(
organic molecules on the active sites was removed via such
treatment, thus recovering the catalytic activity. It is worthy
to mention here that the catalyst was found to be much more
selective for MPO and DPO than the fresh catalyst, after
reactivation with TMAOH. This may suggest that the used
catalyst could not be fully recovered by the treatment with
TMAOH, and a trace amount of reactant and product is still
present on the surface of catalyst, influencing the surface
properties (basicity and/or polarity), and thus changing the
catalytic performance.
Figure 2. FT-IR spectra of the 0.75AEP-MCM-41 catalyst in different
stages: (a) fresh catalyst, (b) used catalyst, which was filtrated, washed
with acetone and dried under vacuum at 343 K after the fourth run,
and (c) TMAOH treated catalyst, i.e. the used catalyst was treated with
-1
0.2 mol L methanol solution of TMAOH for 30 min at room temperature,
then filtrated, Soxhlet-extracted with methanol for 48 h and dried under
vacuum.
of the catalyst might be caused by the reaction of the
It is known that the transesterification of DMO with
1
7
supported propylamine with CO present in air, or with
phenol is an equilibrium reaction. The control of the
reaction parameters has an important impact on the catalytic
properties. Because of the prominent catalytic features
of AEP-MCM-41, it was chosen for further study and its
catalytic properties were investigated in more detail.
Theeffectoftheaminogrouploadingontheperformance
of AEP-MCM-41 catalyst was investigated (Table 4). An
increase in the loadings of AEP group increased the
conversion of DMO. The catalyst 1.02AEP-MCM-41
gave 95.8% conversion of DMO with a high anisole
selectivity of 61.1% after 10 h of reaction (Table 4, entry 4).
Additionally, the density of AEP groups also can affect
their catalytic properties (Table 4, entries 2 and 3). When
the conversion of DMO was kept approximately at 80%
for the 0.75AEP-MCM-41 and 1.02AEP-MCM-41, the
selectivity to anisole reached 29.5% for the sample with
2
some benzoic acid present in the benzaldehyde or produced
by in-situ oxidation.
Figure 2 shows the FT-IR spectra of the fresh, used and
TMAOH treated 0.75AEP-MCM-41 catalysts. Compared
with the fresh catalyst (Figure 2a), it could be seen that
some additional bands (at around 690, 758, 1237, 1365,
-
1
1
498, 1601 and 1757 cm ) are observed in the spectrum of
the used AEP-MCM-41 (Figure 2b). Herein, two bands at
-
1
6
90 and 758 cm might be attributed to the C–H bending
-
1
mode of phenol. The band at 1237 cm was ascribed to the
C–O stretching vibrational mode of phenol and anisole.
The intense adsorption bands at 1498 and 1601 cm were
ascribed to the C=C stretching mode of aromatic ring,
-
1
-
1
while the peak around 1757 cm mainly arose from the
C=O stretching mode of DMO (or methyl phenyl oxalate
4
9
-1
(
MPO), DPO). Moreover, it was found that the color
1.0 mmol g ofAEP groups, which was higher than for the

Vol. 21, No. 12, 2010
Liu et al.
2259
a
Table 4. The catalytic properties of AEP-MCM-41 with different loadings of amino group
Entry
time / h
Loading /
mmol g )
Conversion of
DMO / (%)
Selectivity / (%)
Yield / (%)
-
1 b
(
MPO
81.8
59.6
45.7
15.1
DPO
10.7
26.6
24.8
23.8
anisole
7.5
MPO
48.3
48.2
36.5
14.4
DPO
6.3
1
2
3
10
10
6
0.55
0.75
1.02
1.02
59.0
80.9
79.9
95.8
13.7
29.5
61.1
21.5
19.8
22.8
4
10
a
b
Reaction conditions: catalyst 1.8 g, phenol 0.5 mol, phenol/DMO = 5.0, reaction temperature 453 K. MPO: methyl phenyl oxalate. Based on CHN
elemental analysis.
a
Table 5. The catalytic properties of 1.02AEP-MCM-41 for transesterification of phenol with DMO
Entry
time / h
Conversion of
DMO / (%)
Selectivity / (%)
Yield / (%)
DPO
0
MPO
99.0
45.7
30.8
15.1
DPO
0
anisole
1.0
MPO
20.8
36.5
28.2
14.4
anisole
0.2
1
2
3
2
6
21.0
79.9
91.5
95.8
24.8
25.6
23.8
29.5
43.5
61.1
19.8
23.6
39.8
58.5
8
23.4
4
10
22.8
a
Reaction conditions: catalyst 1.8 g, phenol 0.5 mol, phenol/DMO = 5.0, reaction temperature 453 K. MPO: methyl phenyl oxalate.
catalyst with lower loading of AEP group. These results
suggest that there is an optimum loading such that higher
loadings of amino groups may result in higher selectivity
for the by-product anisole.
under the test conditions. Moreover, the reaction of DPO
and DMO using AEPTMS as catalyst (DPO: 0.0125 mol,
DMO: 0.0125 mol, AEPTMS: 0.675 mmol), also lead to
the formation of anisole.
Based on the reaction data above, it can be found
that these amino-functionalized MCM-41 materials are
active and recyclable for the transesterification of DMO
with phenol. Both the basic strength and density of amino
groups have considerable effects on the catalytic properties
of the hybrid materials. Previously, the mechanism of
the transesterification of DMO with phenol to MPO on
catalysts containing Lewis or Brönsted acid sites has been
The selectivity to anisole was rather low when the
conversion of DMO was kept at relatively low level (e.g.,
40%), thus the formation of anisole by direct reaction
of DMO with phenol should be negligible. Besides,
considering that the methanol produced in the reaction
was removed from the system by distillation in order to
accelerate the desired reaction, the formation of anisole
from the reaction of methanol with phenol should also be
negligible. The reaction of DPO with DMO to produce
anisole should be also unfavorable due to steric effects
of the two large substituents. Thus, we suppose that the
formation of anisole should be mainly due to the reaction
of MPO with phenol. In order to clarify this point, the
catalytic performance of 1.02AEP-MCM-41 in the
reaction time range between 2 and 10 h was monitored
(Table 5). When the conversion of DMO was very low
(i.e., 21%), the selectivity to anisole was quite low (1.0%).
As the reaction proceeded, the conversion of DMO
increased considerably (above 79% after 6 h), while the
selectivity to DPO was almost unchanged. However, the
selectivity to MPO decreased significantly along with
the rapid increase of the selectivity to anisole (Table 5,
entries 2-4). Notably, the total selectivity to MPO and
anisole remained almost steady at about 75% after 6 h
of reaction, implying that there might be a correlation
between MPO and anisole.
1
7,50
proposed by Ma and co-workers.
Here, on the basis
51,52
of some related references,
a plausible mechanism for
the transesterification of phenol with DMO catalyzed by
amino-functionalized materials was proposed. In short, the
amino group acts as Lewis base to assist hydrogen transfer
from phenol to the carbonyl oxygen of DMO forming a
hexahedral intermediate, which then decomposes to form
the main product and methanol.
Notably, anisole is an important by-product in our case,
and it would be significant to understand its formation
mechanism. For this purpose, additional catalytic reactions
were carried out using AEPTMS as homogeneous
catalyst. The reaction of phenol and CH OH performed
3
(
phenol: 0.13 mol, CH OH: 0.067 mol, AEPTMS catalyst:
3
0.9 mmol) at 453 K, gave no detectable amount of anisole
after 10 h. But the reaction of DPO and CH OH carried
3
out (DPO: 0.025 mol, CH OH: 0.1 mol, AEPTMS:
3
0
.675 mmol) at 453 K lead to the formation of anisole

2
260
Comparative Study on the Catalytic Properties of Amino-Functionalized Silica Materials
J. Braz. Chem. Soc.
Conclusions
19. Wang, S. P.; Ma, X. B.; Gong, J. L.; Gao, N.; Guo, H. L.;Yang,
X.; Xu, G. H.; Catal. Today 2004, 93-95, 377.
Insummary, amino-functionalizedmesoporousmaterials
are active and promising heterogeneous catalysts for the
transesterification of DMO with phenol. The main products
MPO and DPO were successfully obtained via a Lewis
base-catalyzed route, in which the amino groups located on
the surface of mesoporous support are the main active sites.
Both the density and basic strength of amino groups have
considerable effects on the catalytic properties of the hybrid
materials. The formation of the by-product anisole might be
attributed to the reaction between MPO and phenol.
20. Sakai, T.; Tsutsumi, Y.; Ema, T.; Green Chem. 2008, 10, 337.
21. Zhang, Y.; Zhao, Y. W.; Xia, C. G.; J. Mol. Catal. A: Chem.
2009, 306, 107.
22. Zhang, Y.; Xia, C. G.; Appl. Catal., A 2009, 366, 141.
23. Blanc, A. C.; Macquarrie, J.; Valle, S.; Renard, G.; Quinn, C.
R.; Brunel, D.; Green Chem. 2000, 2, 283.
24. Carloni, S.; DeVos, D. E.; Jacobs, P.A.; Maggi, R.; Sartori, G.;
Sartorio, R.; J. Catal. 2002, 205, 199.
25. Faria, E. A.; Ramalho, H. F.; Marques, J. S.; Suarez, P. A. Z.;
Prado, A. G. S.; Appl. Catal., A 2008, 338, 72.
2
6. Soldi, L.; Ferstl, W.; Loebbecke, S.; Maggi, R.; Malmassari,
C.; Sartori, G.; Yada, S.; J. Catal. 2008, 258, 289.
Acknowledgments
2
7. Brunel, D.; Microporous Mesoporous Mater. 1999, 27, 329.
This work is supported by the Program for New Century
Excellent Talents in University, the Graduate Innovation
Fund of Jilin University (20091013) and the Natural
Science Foundation of China (20403006, 20773050).
28. Hruby, S. L.; Shanks, B. H.; J. Catal. 2009, 263, 181.
29. Parida, K. M.; Rath, D.; J. Mol. Catal. A: Chem. 2009, 310, 93.
30. Xie, Y. W.; Sharma, K. K.; Anan, A.; Wang, G.; Biradar, A. V.;
Asefa, T.; J. Catal. 2009, 265, 131.
3
1. Suzuki, T. M.; Nakamura, T.; Fukumoto, K.; Yamamoto, M.;
References
Akimoto, Y.; Yano, K.; J. Mol. Catal. A: Chem. 2008, 280,
2
24.
1
2
3
4
. Ono, Y.; Appl. Catal., A 1997, 155, 133.
32. Wang, X. G.; Lin, K. S. K.; Chan, J. C. C.; Cheng, S.; J. Phys.
Chem. B 2005, 109, 1763.
. Gong, J. L.; Ma, X. B.;Wang, S. P.; Appl. Catal., A 2007, 316, 1.
. Shaikh, A. G.; Sivaram, S.; Chem. Rev. 1996, 96, 951.
. Takagi, M.; Miyagi, H.;Yoneyama, T.; J. Mol. Catal. A: Chem.
33. Cauvel, A.; Renard, G.; Brunel, D.; J. Org. Chem. 1997, 62,
749.
1
998, 129, 1.
34. Feng, X. J.; Lu, X. B.; He, R.; Appl. Catal., A 2004, 272, 347.
35. Saravanamurugan, S.; Sujandi; Han, D. S.; Koo, J. B.; Park, S.
E.; Catal. Commun. 2008, 9, 58.
5
6
7
. Ishii, H.; Goyal, M.; Ueda, M.; Takeuchi, K.; Asai, M.; Appl.
Catal., A 2000, 201, 101.
. Linsen, K. J. L.; Libens, J.; Jacobs, P.A.; Chem. Commun. 2002,
36. Sathicq, G.; Musante, L.; Romanelli, G.; Pasquale, G.; Autino,
J.; Thomas, H.; Vazquez, P.; Catal. Today 2008, 133-135, 455.
37. Hagiwara, H.; Koseki, A.; Isobe, K.; Shimizu, K.; Hoshi, T.;
Suzuki, T.; Synlett 2004, 12, 2188.
2
728.
. Yasuda, H.; Maki, N.; Choi, J. C.; Sakakura, T.; J. Organomet.
Chem. 2003, 682, 66.
8
. Xue, W.; Wang,Y. J.; Zhao, X. Q.; Catal. Today 2005, 105, 724.
. Fu, Z. H.; Ono, Y.; J. Mol. Catal. A: Chem. 1997, 118, 293.
38. Liu, Y.; Zhao, G. M.; Liu, G.; Wu, S. J.; Chen, G. H.; Zhang,
W. X.; Sun, H. Y.; Jia, M. J.; Catal. Commun. 2008, 9, 2022.
39. Lin, W.Y.; Cai, Q.; Pang, W. Q.;Yue,Y.; Chem. Commun. 1998,
2473.
9
1
0. Kim, W. B.; Lee, J. S.; Catal. Lett. 1999, 59, 83.
1. Li, Z. H.; Cheng, B. W.; Su, K. M.; Gu, Y.; Xi, P.; Guo, M. L.;
J. Mol. Catal. A: Chem. 2008, 289, 100.
1
40. Zhang, L.; Liu, J.; Yang, J.; Yang, Q. H.; Li, C.; Microporous
Mesoporous Mater. 2008, 109, 172.
1
1
2. Kim, Y. T.; Park, E. D.; Appl. Catal., A 2009, 356, 211.
3. Keigo, N.; Shuji, T.; Katsumasa, H.; Ryoji, S.; US pat. 5,834,615
41. Jia, M. J.; Seifert, A.; Thiel, W. R.; Chem. Mater. 2003, 15,
2174.
1
998.
1
1
1
1
1
4. Keigo, N.; Shuji, T.; Katsumasa, H.; Ryoji, S.; Akinori, S.;
Katsutoshi, W.; US pat. 5,922,827 1999.
42. Jia, M. J.; Seifert, A.; Berger, M.; Giegengack, H.; Schulze, S.;
Thiel, W. R.; Chem. Mater. 2004, 16, 877.
5. Zhao, G. M.; Zhu, X. M.; Wang, Z. L.; Liu, G.; Liu,Y.; Jia, M.
J.; Zhang, W. X.; React. Kinet. Catal. Lett. 2007, 91, 77.
6. Liu,Y.; Wang, S. P.; Ma, X. B.; Ind. Eng. Chem. Res. 2007, 46,
43. Chong, A. S. M.; Zhao, X. S.; J. Phys. Chem. B 2003, 107,
12650.
44. Bae, J. A.; Song, K. C.; Jeon, J. K.; Ko,Y. S.; Park,Y. K.;Yima,
J. H.; Microporous Mesoporous Mater. 2009, 123, 289.
45. Gregg, S. J.; Sing, K. S. W.; Adsorption, Surface Area and
1
045.
7. Wang, S. P.; Ma, X. B.; Guo, H. L.; Gong, J. L.;Yang, X.; Xu,
G. H.; J. Mol. Catal. A: Chem. 2004, 214, 273.
nd
Porosity, 2 ed., Academic Press: London, 1982.
8. Liu, G.; Liu, Y.; Yang, G.; Li, S. Y.; Zu, Y. H.; Zhang, W. X.;
Jia, M. J.; J. Phys. Chem. C 2009, 113, 9345.
46. Chen, Y.; Han, J. Y.; Zhang, H. T.; Appl. Surf. Sci. 2007, 253,
9400.

Vol. 21, No. 12, 2010
Liu et al.
2261
4
4
7. Srivastava, R.; Srinivas, D.; Ratnasamy, P.; Microporous
Mesoporous Mater. 2006, 90, 314.
51. Lai, C. L.; Lee, H. M.; Hu, C. H.; Tetrahedron Lett. 2005, 46,
6265.
8. Sartori, G.; Bigi, F.; Maggi, R.; Sartorio, R.; Macquarrie, D.
J.; Lenarda, M.; Storaro, L.; Coluccia, S.; Martra, G.; J. Catal.
52. Chuma,A.; Horn, H. W.; Swope, W. C.; Pratt, R. C.; Zhang, L.;
Lohmeijer, B. G. G.; Wade, C. G.; Waymouth, R. M.; Hedrick,
J. L.; Rice, J. E.; J. Am. Chem. Soc. 2008, 130, 6749.
2
004, 222, 410.
4
9. Beutel, T.; J. Chem. Soc., Faraday Trans. 1998, 94, 985.
0. Liu, Y.; Ma, X. B.; Wang, S. P.; Gong, J. L.; Appl. Catal., B
5
Submitted: November 24, 2009
2
007, 77, 125.
Published online: September 21, 2010