One-pot multistep cascade reactions over multifunctional nanocomposites with pd nanoparticles supported on amine-modified mesoporous silica

Article abstract of DOI:10.1002/asia.201300514

Two kinds of multifunctional nanocomposites, SBA-15-NH₂/Pd-p and SBA-15-NH₂/Pd-f, with platelet-like and fiber-like morphologies, respectively, were fabricated by immobilizing Pd NPs onto amine-functionalized SBA-15. Some of the amino groups acted as anchoring sites for Pd NPs, whilst the remaining groups acted as Bronsted basic sites. As a result, the composites served as excellent multifunctional heterogeneous catalysts for one-pot multistep cascade reaction sequences. Moreover,when diffusion was the rate-determine step, SBA-15-NH₂/Pd-p, with small mesopores, was superior to the fiber-like control sample, owing to its short diffusion length, a lower possibility of pore clogging, and better mass transportation for the reaction species during the catalysis.

Full text of DOI:10.1002/asia.201300514

FULL PAPER
FULL PAPER
Convert to Pd-f: Two kinds of multi-
functional nanocomposites, SBA-15-
NH /Pd-p and SBA-15-NH /Pd-f, with
platelet-like and fiber-like morpholo-
gies, respectively, were fabricated by
immobilizing Pd NPs onto amine-func-
tionalized SBA-15. These composites
were excellent multifunctional hetero-
geneous catalysts for one-pot multistep
cascade reaction sequences.
Heterogeneous Catalysis
Ping Li, Hua Liu, Yu Yu,
Chang-Yan Cao,
Wei-Guo Song*
2
2
&&&& — &&&&
One-Pot Multistep Cascade Reactions
over Multifunctional Nanocomposites
with Pd Nanoparticles Supported on
Amine-Modified Mesoporous Silica
Chem. Asian J. 2013, 00, 0 – 0
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Wei-Guo Song et al.
DOI: 10.1002/asia.201300514
One-Pot Multistep Cascade Reactions over Multifunctional Nanocomposites
with Pd Nanoparticles Supported on Amine-Modified Mesoporous Silica
[
a, b]
[a, b]
[a, b]
[a]
[a]
Ping Li,
Hua Liu,
Yu Yu,
Chang-Yan Cao, and Wei-Guo Song*
Dedicated to Prof. Chun-Li Bai on the occasion of his 60th birthday
Abstract: Two kinds of multifunctional
nanocomposites, SBA-15-NH /Pd-p
acted as Brønsted basic sites. As
a result, the composites served as ex-
cellent multifunctional heterogeneous
catalysts for one-pot multistep cascade
reaction sequences. Moreover, when
diffusion was the rate-determine step,
2
and SBA-15-NH /Pd-f, with platelet-
SBA-15-NH /Pd-p, with small meso-
2
2
like and fiber-like morphologies, re-
spectively, were fabricated by immobi-
lizing Pd NPs onto amine-functional-
ized SBA-15. Some of the amino
groups acted as anchoring sites for
Pd NPs, whilst the remaining groups
pores, was superior to the fiber-like
control sample, owing to its short diffu-
sion length, a lower possibility of pore
clogging, and better mass transporta-
tion for the reaction species during the
catalysis.
Keywords: diffusion
·
heteroge-
neous catalysis · mesoporous mate-
rials · nanoparticles · palladium
Introduction
cally required for Pd NPs. Owing to its highly ordered meso-
pores, large surface area, relatively large pore sizes, and
higher hydrothermal stability, mesoporous silica SBA-15
[32,33]
The design of multifunctional catalysts for one-pot multistep
reactions to produce target products is highly desirable in
has become a desirable solid support for Pd NPs. Moreover,
to help disperse and stabilize the supported Pd NPs, func-
tional groups (such as amino, thiol, and vinyl groups) are
[1–10]
organic synthesis.
The use of multifunctional catalysts
can remarkably simplify the synthetic procedures, by de-
creasing the number of separation and purification steps,
producing less waste, and leading to lower overall cost.
Among the various multifunctional heterogeneous cata-
lysts that have been reported, most have focused on acid–
[34–37]
usually incorporated into the mesoporous walls.
These
organic functional groups can provide stronger anchoring
sites for attaching Pd NPs in comparison with pristine silica.
In addition, the functional groups can provide additional
catalytically active sites to couple or cooperate with the
[1,5–18]
base and metal–acid bifunctional catalysts
are there are
only very few reports about metal–base bifunctional cata-
lysts, which will be the focus of our study.
With regards to metal nanoparticles, palladium nanoparti-
Pd NPs for multifunctional catalysis, for example, sulfonic
[19]
[38,39]
acid groups as acidic sites
or amine groups as basic
[11]
sites.
cles (Pd NPs) have shown excellent activities in many reac-
The pore lengths in SBA and other types of mesoporous
silica with conventional morphologies are typically of the
order of several micrometers, which result in long diffusion
and residence times of the reaction species. Thus, shorter
pore lengths in the materials may be particularly desirable
for catalysis in some cases, because they offer quicker mass
[20–24]
tions, such as carbonÀcarbon coupling reactions,
oxida-
How-
[25–28]
[29–31]
tion reactions,
and hydrogenation reactions.
ever, during the catalysis, Pd NPs are prone to aggregation
into larger particles, thereby leading to a remarkable de-
crease in their catalytic activities. Moreover, tiny nanoparti-
cles are also difficult to recycle. Therefore, supports are typi-
[39–43]
transportation and, thus, faster reactions.
[
a] P. Li, H. Liu, Y. Yu, Dr. C.-Y. Cao, Prof. Dr. W.-G. Song
Beijing National Laboratory for Molecular Sciences (BNLMS)
Key Laboratory of Molecular Nanostructure and
Nanotechnology, Institute of Chemistry
Chinese Academy of Sciences
Beijing, 100190 (P. R. China)
Tel and Fax: (+86)10-6255-7908
E-mail: wsong@iccas.ac.cn
Herein, we report a straightforward method for the prepa-
ration of a new class of multifunctional metal-nanoparticle-
based catalysts by supporting Pd NPs onto the amino-func-
tionalized SBA-15 material with two different morphologies.
The amino groups that are incorporated into the mesopo-
rous silica play two roles: Some act as anchoring sites for
stabilizing the tiny Pd NPs against aggregation and leaching,
[
b] P. Li, H. Liu, Y. Yu
Graduate University of Chinese Academy of Sciences
Beijing, 100049 (P. R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300514.
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Wei-Guo Song et al.
whilst the remaining groups act as Brønsted basic sites and
are covalently anchored onto the silica support. As a result,
the multifunctional nanocomposite showed excellent catalyt-
ic activity in one-pot multistep cascade reactions for the syn-
thesis of a-alkylated nitriles [Equation (1)]. Moreover, for
diffusion-controlled reactions, the catalyst with a platelet-
like morphology (SBA-15-NH /Pd-p) was superior to the
2
fiber-like sample (SBA-15-NH /Pd-f), whereas, in the case of
2
reactivity-controlled reactions, the differences between the
catalytic activities of the two catalysts with different mor-
phologies were much less clear.
Results and Discussion
Figure 1. SEM and TEM images of a–c) SBA-15-NH
NH /Pd-p. Inset in (f) shows a high-magnification image of SBA-15-NH
Pd-p.
2
-p and d–f) SBA-15-
The synthesis route to the multifunctional platelet-like SBA-
2
2
/
1
5-NH /Pd-p material is briefly schematically represented in
2
Scheme 1. First, amino-functionalized SBA-15 platelets
SBA-15-NH -p) were prepared by a P123-directed co-con-
(
2
and TEM images (Figure 1d–f), the SBA-15-NH -p support
2
maintained its original morphology and highly ordered mes-
opores. Although EDX (see the Supporting Information,
Figure S1) and XPS analysis (see the Supporting Informa-
tion, Figure S5) confirmed the existence of elemental Pd,
almost no Pd NPs were observed in the high-magnification
TEM images (Figure 1 f, inset), owing to the highly uniform
dispersion of tiny Pd NPs, in agreement with the wide-angle
XRD results (see the Supporting Information, Figure S2),
because no diffraction peaks that were indicative of a metal-
lic Pd phase were detected.
2
Scheme 1. Synthesis procedure for the SBA-15-NH /Pd-p catalyst.
densation between tetraethyl orthosilicate (TEOS) and 3-
aminopropyltrimethoxysilane (APTMS) in the presence of
Zr and NaCl. Then, the Pd NPs were supported onto SBA-
From the SEM and TEM images (Figure 2a,b), SBA-15-
NH -f was found to be formed as fiber-like aggregates, with
2
IV
1
5-NH -p by using a simple adsorption/reduction procedure.
2
A similar approach was employed for the preparation of
multifunctional fiber-like SBA-15-NH /Pd-f, but without the
2
IV
addition of Zr . For comparison, a series of control materi-
als with comparable concentrations of the catalytically
active sites, that is, monofunctional catalysts SBA-15-NH -p
2
and SBA-15/Pd-p, were produced. Moreover, pure SBA-15-
p, without any functionalities, was also prepared (for details,
see the Experimental Section).
The samples were systematically characterized by SEM,
TEM, nitrogen-adsorption/desorption measurements, wide-
angle X-ray diffraction (WAXRD), small-angle X-ray dif-
1
3
29
fraction (SAXRD), solid-state C and Si NMR spectrosco-
py, elemental analysis, inductively coupled plasma atomic
emission spectroscopy (ICP-AES), and X-ray photoelectron
spectroscopy (XPS). Detailed characterization data are pro-
vided in the Supporting Information.
The SEM images (Figure 1a) showed that the SBA-15-
NH -p material had a hexagonal platelet morphology
2
(
width: 500–800 nm, thickness: 250–350 nm). The TEM
images (Figure 1b,c) showed that the mesochannels were
well-ordered and aligned along the short axis of the platelet.
2
Figure 2. SEM and TEM images of a,b) SBA-15-NH -f and c,d) SBA-15-
After the adsorption/reduction of H PdCl , Pd NPs were
2
4
NH /Pd-f. Inset in (d) shows a high-magnification image of SBA-15-NH /
2
2
supported onto the SBA-15-NH -p. As shown in the SEM
Pd-f.
2
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Wei-Guo Song et al.
heavily interconnected channels, thus leading to very
lengthy channels of tens of micrometers in length. After
functionalization with Pd NPs, the fiber-like morphology
and mesoporous structure were well-retained (Figure 2c,d).
Similar to SBA-15-NH /Pd-p, the Pd NPs in SBA-15-NH /
Pd-p were extremely small so that no Pd NPs were detected
in the TEM image, although EDX analysis (see the Support-
ing Information, Figure S3) confirmed the presence of Pd
species.
the (100), (110), and (200) reflections of the hexagonal
structure for SBA-15.
Solid-state NMR spectroscopy was used to confirm the
[
38,44]
presence of the desired functional groups.
The solid-
2
9
state Si NMR spectrum of SBA-15-NH /Pd-p is shown in
2
2
2
2
3
Figure 3c. T and T peaks, which appeared at d=À58 and
(OSi)
À67 ppm, were assigned to RÀSi
A
H
U
G
R
N
U
G
ACHTUNGTRENNUNG
2
3
2
organosiloxane species, respectively. The presence of T and
3
T peaks confirmed that the organic silanes were incorporat-
1
3
Figure 3a and the Supporting Information, Figure S4,
show the nitrogen-sorption isotherms and the corresponding
pore-size distributions of SBA-15-NH -p and SBA-15-NH /
ed into the silica wall structure. The solid-state C NMR
spectrum (Figure 3d) confirmed the successful grafting of
aminopropyl groups onto the silica surface. Elemental analy-
2
2
Pd-p. Both materials displayed classical type-IV isotherms
sis and ICP-AES analysis of SBA-15-NH /Pd-p showed that
2
the nitrogen and palladium con-
tent were 1.30 and 3.60 wt.%,
respectively. Pd 3d and N 1s
XPS spectra (see the Support-
ing Information, Figure S5)
demonstrated that palladium
0
existed in its Pd form and that
nitrogen existed as amino
groups.
Next, we explored the cata-
lytic performance of SBA-15-
NH /Pd-p as base–metal bifunc-
2
tional catalyst. The one-pot
multistep synthesis of a-alkylat-
ed nitriles was selected as
a
model reaction [Equa-
tion (1)]. The reaction sequence
was composed of two steps:
Knoevenagel condensation of
nitriles with carbonyl com-
pounds on the basic sites and
hydrogenation of a,b-unsaturat-
ed nitriles on the Pd NPs. First-
ly, the catalytic activity of SBA-
1
5-NH /Pd-p was compared
2
with a series of control samples
Figure 3. Characterizations of SBA-15-NH
2 2
/Pd-p: a) N -adsorption/desorption isotherms; inset shows the cor-
responding BJH pore-size distribution, as obtained from the desorption data. b) Small-angle XRD pattern. in the reaction between benzal-
2
9
2
3
2
3
4
c) Solid-state Si NMR spectrum (T : d=À58 ppm, T : d=À67 ppm, Q : d=À90 ppm, Q : d=À100 ppm, Q : dehyde and ethyl cyanoacetate;
1
3
d=À109 ppm). d) Solid-state C NMR spectrum. Asterisks denote residual surfactant and uncondensed me-
the results are summarized in
Table 1.
thoxy/ethoxy groups.
The SBA-15-NH /Pd-p nano-
2
composite converted benzalde-
with clear H1 hysteresis loops (0.6<P/P <0.8), which were
hyde into the desired product in high yield (Table 1,
entry 1), thus showing excellent catalytic activity and selec-
tivity of our bifunctional composite. Interestingly, neither
0
characteristic of large mesoporous structures. The BET sur-
face area, pore volume, and average pore diameter of SBA-
2
À1
3
À1
1
5-NH /Pd-p were 714 m g , 1.06 cm g , and 6.55 nm, re-
monofunctional catalysts SBA-15-NH -p nor SBA-15/Pd-p
2
2
spectively, which were comparable to those of the SBA-15-
converted the reactant (A1) into the desired product (C1;
Table 1, entries 3 and 4), although the hydrogenation reac-
tion of benzaldehyde into benzyl alcohol proceeded smooth-
ly in the presence of SBA-15/Pd-p. However, the control hy-
drogenation reaction starting from B1 demonstrated that
SBA-15/Pd-p was an excellent catalyst for converting B1
into C1 through a catalytic hydrogenation reaction (Table 1,
2
À1
3
À1
NH -p support (771 m g , 1.05 cm g , and 6.57 nm, respec-
2
tively). These results further suggested a uniform dispersion
of Pd nanoparticles over the support so that the deposition
of nanoparticles did not the block mesopores and destroy
the structure of the support. The mesoporous structure was
also confirmed by small-angle XRD (Figure 3b), which
showed three intense diffraction peaks that were indexed as
entry 5). Moreover, a physical mixture of SBA-15-NH -p
2
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Wei-Guo Song et al.
Table 1. One-pot Knoevenagel condensation/hydrogenation multistep
cascade reaction sequence between benzaldehyde and ethyl cyanoacetate
catalyzed by various catalysts.
mation, Figures S2, S6–S8 and Table S1). The catalytic per-
formance of short-channeled SBA-15-NH /Pd-p and
2
[
a]
lengthy-channeled SBA-15-NH /Pd-f were investigated in
2
two Knoevenagel condensation reactions, that is, between p-
methoxybenzaldehyde and ethyl cyanoacetate and between
4
-(trifluoromethyl)benzaldehyde and ethyl cyanoacetate,
under identical experimental conditions. To evaluate the cat-
alytic activities of the two catalysts, the reaction conditions
were chosen to be mild so that the conversion was about
50% (for details, see the Experimental Section). Figure 4a,b
shows a plot of the product yield over two samples as a func-
tion of reaction time. In the reaction between p-methoxy-
Entry Catalyst
Conversion
Yield of B1 Yield of C1
[%]
[%]
[%]
[
g]
g]
1
2
SBA-15-NH
SBA-15-NH
2
2
/Pd-p
/Pd-p
100
95
0
7
100
88
[
[
b]
(5th)
3
4
5
6
7
SBA-15-NH
SBA-15/Pd-p
SBA-15/Pd-p
2
-p
100
100
0
–
0
70
0
0
benzaldehyde and ethyl cyanoacetate, SBA-15-NH /Pd-p ex-
2
[
c]
100
[
d]
[g]
hibited significantly higher activity than SBA-15-NH /Pd-f,
2
100
100
96
100
100
26
[
e]
[g]
whereas, in the case of 4-(trifluoromethyl)benzaldehyde, the
difference between the catalytic activities was much less
clear.
physical mixture
physical mixture
[
g]
[
f]
(3rd)
8
SBA-15-p
0
0
0
The differences in activity in Figure 4a, as well as the ap-
parently no difference in Figure 4b, are two excellent exam-
ples of diffusion control versus reactivity control in hetero-
geneous catalysis. For Knoevenagel condensation reactions,
[
(
3
a] Reaction conditions: Ethyl cyanoacetate (0.5 mmol), benzaldehyde
0.5 mmol), toluene (10 mL), catalyst (30 mg), 808C, 30 min, then 708C,
0 min, H (1 atm). Yields were determined by GC. [b] The 5th cycle of
2
the catalyst in entry 1. [c] A1 was converted into benzyl alcohol. [d] For
the hydrogenation reaction alone, starting from B1. [e] Physical mixture
[11,45]
p-methoxybenzaldehyde is a very active substrate
and
of SBA-15-NH
sites and Pd sites as SBA-15-NH
entry 5. [g] Approximate value.
2
-p and SBA-15/Pd-p with a comparable number of basic
the diffusion into the basic sites controls the reaction rate.
2
/Pd-p. [f] The 3rd cycle of the catalyst in
Thus, SBA-15-NH /Pd-p, with a short diffusion length and
2
and SBA-15/Pd-p with similar concentrations of active
Table 2. One-pot multistep reaction sequences that are composed of base-catalyzed
Knoevenagel condensation and Pd-catalyzed hydrogenation reactions by using SBA-15-
sites as the SBA-15-NH /Pd-p nanocomposite showed
2
[a]
NH
2
/Pd-p as a catalyst.
comparable catalytic performance in the first run (Table 1,
entry 6). However, the physical mixture exhibited poor
stability and recyclability (Table 1, entry 7), presumably
because the interactions between the Pd NPs and the pure
mesoporous silica support without any organic groups
were relatively weak, thus leading to serious aggregation
and leaching of the Pd species during the catalysis.
1
Entry
R
Carbonyl compound
t
(
[
Product
Yield
[%]
step 1)
min]
1
2
CO
CO
2
Et
Et
30
99
97
2
2
20
20
Then, the versatility of the SBA-15-NH /Pd-p nanocom-
2
posite as multifunctional catalyst was investigated. As
summarized in Table 2, in the presence of SBA-15-NH2/
Pd-p, various a-alkylated nitriles were obtained through
two-step cascade reactions in a single pot. Aromatic alde-
hydes with both electron-rich and electron-deficient sub-
stituents (Table 2, entries 1–6 and 9) served as good sub-
strates and were converted into the desired products in
very high yields. In addition to aromatic aldehydes, both
aliphatic aldehydes and ketones also proceeded smoothly
in the reactions with nitriles and gave excellent yields of
the corresponding products (Table 2, entries 7 and 8), thus
3
4
5
CO
CO
CO
Et
Et
Et
98
98
99
2
2
100
40
6
7
8
9
CO
CO
2
2
Et
Et
60
20
90
30
97
98
93
98
demonstrating that the SBA-15-NH /Pd-p nanocomposite
2
served as an efficient bifunctional catalyst for tandem cat-
alysis.
In addition, to assess the influence of the morphology
of the catalyst on its catalytic activity, a control sample,
CN
CN
SBA-15-NH /Pd-f, with similar Pd loading, BET surface
2
area, pore volume, average pore diameter, and a compara-
ble number of amino groups, but with a fiber-like mor-
phology and, hence, lengthier channels, was employed (for
detailed characterization data, see the Supporting Infor-
[
(
a] Reaction conditions: Nitrile (0.5 mmol), carbonyl compound (0.5 mmol), toluene
2 2
10 mL), SBA-15-NH /Pd-p (30 mg), (1) 808C, t, then (2) 708C, 30 min, H (1 atm). Yields
were determined by GC.
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Wei-Guo Song et al.
Figure 5. a) Recycling test of the SBA-15-NH
2
/Pd-p catalyst in a one-pot,
two-step cascade reaction sequence between benzaldehyde and ethyl cya-
noacetate. b) TEM image of the SBA-15-NH
used repetitively for five 5 cycles.
2
/Pd-p catalyst after being
pseudo-ligands by non-covalent binding with Pd NPs and
this coordination effect between them effectively suppressed
the leaching of Pd from the support and the aggregation of
Pd NPs during the catalysis.
Conclusions
In summary, we have produced a nanocomposite system in
which Pd NPs were deposited onto amine-modified mesopo-
rous silica SBA-15 and used it as an excellent multifunction-
al catalyst system for the one-pot multistep synthesis of a-al-
kylated nitriles. The amino groups that were functionalized
on the silica helped tiny Pd NPs to be tightly anchored on
the support with high dispersion, which greatly enhanced
the catalytic activity and recyclability. Excess amino groups
served as basic catalytic sites. For diffusion-controlled reac-
tions, the platelet-like sample with a short diffusion length
Figure 4. Plot of the yields of the catalytic reactions between a) p-me-
thoxybenzaldehyde and ethyl cyanoacetate and b) 4-(trifluoromethyl)-
benzaldehyde and ethyl cyanoacetate over SBA-15-NH
5-NH /Pd-f as a function of reaction time.
2
/Pd-p and SBA-
1
2
better mass-transport ability, had an advantage over SBA-
5-NH /Pd-f, which a had much-longer diffusion length/time.
1
(SBA-15-NH /Pd-p) was superior to the fiber-like material
2
2
Whereas in the case of 4-(trifluoromethyl)benzaldehyde,
with lengthy mesopores (SBA-15-NH /Pd-f), whereas, for
2
[45,46]
which was a quite-inactive substrate,
the catalytic reac-
the reactivity-controlled reactions, the influences of mor-
phology or the diffusion length on the catalytic activity was
less clear.
tion on the basic sites was slow, so that the diffusion into the
basic sites became less influential and the two samples with
different morphologies appeared to have comparable cata-
lytic activities.
The one-pot, two-step cascade reaction sequence between
Experimental Section
benzaldehyde and ethyl cyanoacetate over SBA-15-NH /Pd-
2
Catalyst Synthesis
p was examined to evaluate the stability of the multifunc-
tional catalyst. The used catalyst was easily recovered from
the reaction mixture by centrifugation and the recycling
tests showed that the catalyst could be reused at least five
times without significant loss of the catalytic activity or se-
lectivity (Table 1, entry 2, and Figure 5a). Pd leaching into
the mother liquid after each run was determined by ICP-
AES analysis and the results indicated that the Pd content
in each run was very low (below the detection limit of
SBA-15-NH
2
/Pd-p
In typical synthesis, Pluronic P123 (4 g), NaCl (4.8 g), and
a
ZrOCl ·8H O (0.65 g) were dissolved in 2m HCl (160 mL). Then, TEOS
8.4 g) was added to the solution. After undergoing pre-hydrolysis for 2 h
2
2
(
at 408C, APTMS (1 mL) was introduced, followed by vigorous stirring at
408C for 24 h and aging at 1008C for a further 24 h. The solid precipitate
was collected by filtration and the template was removed by extraction
with EtOH for 48 h.
The resultant extracted SBA-15-NH
for Pd NPs by using a simple adsorption/reduction method. Typically,
SBA-15-NH -p (200 mg) and H PdCl (0.0564m) were added into deion-
ized water (100 mL). After stirring for 1 h, a freshly prepared aqueous so-
2
-p material was used as a support
0.03 ppm). Moreover, the TEM image of the SBA-15-NH2/
Pd-p catalyst after 5 runs (Figure 5b) showed that the
Pd NPs were still highly dispersed with an average diameter
of less than 5 nm. The aminopropyl groups could act as
2
2
4
lution of NaBH
4
(20 mm) was added and the resultant reaction mixture
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Wei-Guo Song et al.
2
+
was stirred for a further 0.5 h to ensure the complete reduction of Pd
zu ICPE-9000. The surface electronic states were analyzed by using XPS
on an ESCALab220i-XL.
ions. The final product was filtered, washed with excess deionized water,
and dried under vacuum overnight.
SBA-15-NH
2
/Pd-f
The control sample SBA-15-NH
2
/Pd-f was prepared by following the
same preparation method as for the SBA-15-NH /Pd-p material, but
Acknowledgements
2
without the addition of ZrOCl
2
·8H
2
O and NaCl.
We are grateful for financial support from the National Basic Research
Program of China (2009CB930400), the National Natural Science Foun-
dation of China (NSFC, 21121063), and the Chinese Academy of Scien-
ces (KJCX2-YW-N41).
SBA-15-p
The control sample SBA-15-p was prepared by following the same prepa-
ration method as for the SBA-15-NH
tion of APTMS.
2
-p material, but without the addi-
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[
a glass reactor. The resulting reaction mixture was vigorously stirred for
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2
1
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2
010S) on a capillary column (DB-5 ms, 30.0 mꢁ320 mmꢁ0.25 mm).
1
Comparison of the catalytic activity between SBA-15-NH
2
/Pd-p and SBA-
1
5-NH /Pd-f with different morphologies and mesochannel lengths
2
2
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1
2
2
9
168.
experimental conditions. Smaller amounts of catalyst and lower reaction
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Characterization
2
SEM images were recorded on a JEOL-6701F scanning electron micro-
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Published online: && &&, 0000
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ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!