Pd nanoparticles immobilized on sepiolite by ionic liquids: Efficient catalysts for hydrogenation of alkenes and Heck reactions

Article abstract of DOI:10.1039/b811587g

Palladium-sepiolite catalysts were prepared by immobilizing Pd²⁺ on sepiolite using an ionic liquid containing a guanidine cation, followed by reduction with hydrogen at 150 °C. The resulting composites were characterized by different techniques. X-Ray photoelectron spectroscopy analysis showed that the loaded Pd existed mainly in the form of Pd⁰, with a small amount of its oxides, and distributed uniformly on sepiolite with particle size about 5 nm, as confirmed by transmission electron microscopy examination. X-Ray diffraction analysis indicated that the sepiolite retained its original structure after deposition of Pd nanoparticles. The activities of the Pd-sepiolite catalysts for hydrogenations of some alkenes (e.g., cyclohexene and 1,3-cyclohexdiene) and Heck reactions were investigated. It was demonstrated that the as-prepared catalysts exhibited very high efficiency for these reactions.

Full text of DOI:10.1039/b811587g

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www.rsc.org/greenchem | Green Chemistry
Pd nanoparticles immobilized on sepiolite by ionic liquids: efficient catalysts
for hydrogenation of alkenes and Heck reactions
Ranting Tao, Shiding Miao, Zhimin Liu,* Yun Xie, Buxing Han, Guimin An and Kunlun Ding
Received 8th July 2008, Accepted 1st October 2008
First published as an Advance Article on the web 12th November 2008
DOI: 10.1039/b811587g
2
+
Palladium-sepiolite catalysts were prepared by immobilizing Pd on sepiolite using an ionic liquid
◦
containing a guanidine cation, followed by reduction with hydrogen at 150 C. The resulting
composites were characterized by different techniques. X-Ray photoelectron spectroscopy analysis
0
showed that the loaded Pd existed mainly in the form of Pd , with a small amount of its oxides,
and distributed uniformly on sepiolite with particle size about 5 nm, as confirmed by transmission
electron microscopy examination. X-Ray diffraction analysis indicated that the sepiolite retained
its original structure after deposition of Pd nanoparticles. The activities of the Pd-sepiolite
catalysts for hydrogenations of some alkenes (e.g., cyclohexene and 1,3-cyclohexdiene) and Heck
reactions were investigated. It was demonstrated that the as-prepared catalysts exhibited very high
efficiency for these reactions.
14
Introduction
range of aldehyde and ketone substrates. Metal nanoparticles
e.g. Pd, Rh, Ru, etc.) were supported on different solid supports
(
With the development of green chemistry, the design and
preparation of green catalysts have attracted much attention
recently, among which heterogeneous catalysts have been widely
investigated. Natural clays are environmentally friendly materi-
als, which are good catalyst supports because of their crystalline
structures and large surface areas. Sepiolite, a kind of natural
with the aid of ILs, exhibiting high efficiency for hydrogenations
15,16
of alkenes and arenes.
The main advantage of using the
supported IL system is that it requires significantly reduced
amounts of the ionic media, which is favorable from an economic
and toxicological point of view.
In our previous work, we developed an approach to support
noble metal nanoparticles (e.g., Ru, Rh) on natural clays by
ILs, and the resultant catalysts showed high efficiency for
clay mineral with a formula of Si12Mg
has a very special place among natural clay minerals due to
its relatively high surface area and excellent ability to adsorb
molecular, ionic, and polymeric species. Similar to other types
of silicate minerals, it contains continuous two-dimensional
8
O
30(OH)
6
(OH
2
)
4
·8H
2
O,
16
17
hydrogenations of benzene and cyclohexene. In this work,
we extended this approach to immobilize Pd nanoparticles on
sepiolite with the aid of an IL, aiming at developing new green
catalysts. The as-prepared Pd catalysts were characterized in
detail by different techniques, including X-ray photoelectron
spectroscopy (XPS), thermogravimetric analysis (TG), scanning
electron microscopy (SEM), transmission electron microscopy
1,2
tetrahedral sheets of T
2
O
5
(T = Si, Al, Be,…), but has no
3
continuous octahedral sheets. Owing to its special structure
and properties, sepiolite has been widely used in a variety of
4–6
industrial applications.
Ionic liquids (ILs), possessing negligible vapor pressure,
reasonable thermal stability, strong ability to dissolve a wide
range of organic, inorganic and organometallic compounds,
(
TEM), inductively coupled plasma-atomic emission spectrom-
eter (ICP-AES), X-ray diffraction (XRD), N sorption, and
2
their catalytic activities for hydrogenations of alkenes and Heck
reactions were investigated. The combination of sepiolite as a
support with an IL may widen the application of sepiolite and
help develop new kinds of green catalysts as well.
7,8
have promising applications in many fields. In particular,
ILs offer new opportunities for the development of catalytic
materials. In industrial processes, heterogeneous catalysis is gen-
erally preferred to homogeneous catalysis, since the separation
9
of the product and recovery of the catalyst are made easier.
Therefore, the immobilization of ILs onto solid supports and the
preparation of heterogeneous catalysts assisted by ILs have at-
Experimental
10–12
tracted significant attention.
For example, Brønsted acid ILs
Starting materials
were immobilized on solid supports, which displayed excellent
recyclability and high activity for a range of esterification and
The sepiolite clay, provided by the Mingyang company, was first
treated as follows. 10 g of sepiolite was immersed in 20 mL
13
nitration reactions. Choline hydroxide was supported on MgO
and shown to be an efficient catalyst for the aldol reaction for a
of 1 M HNO solution at room temperature with stirring for
3
2
4 h. Then, the suspension was filtered and the resulting solid
was washed with deionized water for ten times before drying at
◦
1
05 C for 24 h. The treated clay was pulverized and sieved down
Institute of Chemistry, The Chinese Academy of Sciences, Beijing,
1
00190, China. E-mail: liuzm@iccas.ac.cn
to 120 mesh, which was designated as SH.
9
6 | Green Chem., 2009, 11, 96–101
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Other reagents including HNO
3
(65%–68%), HCl (36%–
Catalytic activity test
3
8%), PdCl , cyclohexene (AR), N,N-dimethylformamide (AR),
2
To evaluate the catalytic characteristics of the as-prepared
samples, hydrogenations of some alkenes (e.g., cyclohexene, 1,3-
cyclohexdiene, styrene and 1-hexene) and Heck reactions were
investigated. Hydrogenation reactions were carried out in a
methyl acrylate (AR) and triethylamine (AR) were pur-
chased from the Beijing Chemical Reagent Company. 1,3-
Cyclohexdiene was obtained from ACROS, and iodoben-
zene (98%) was provided by Alfa Aesar. The ILs (including
5
0 mL stainless steel autoclave with a magnetic stirrer at 300 rpm.
+
-
1
,1,3,3-tetramethylguanidine trifluoroacetic acid, TMG TFA ;
In a typical experiment, 12 mmol of alkene and the required
amount of catalyst were placed in the reactor, and the air in the
+
-
1
,1,3,3-tetramethylguanidine lacticacid, TMG LA and 1,1,3,3-
+
-
tetramethylguanidine acetic acid, TMG AA ) were synthe-
sized directly by neutralization of 1,1,3,3-tetramethylguanidine
reactor was then replaced by H
2
five times. After H was charged
2
into the reactor up to 2.0 MPa, the reactor was moved to an oil
bath at the desired temperature. The temperature of the oil bath
was controlled with a temperature controller (Haake D3) with
(
TMG) with proportionable acid based on the procedures
18,19
reported previously.
◦
an accuracy of 0.1 C. The pressure of the reaction system was
monitored using a pressure transducer (Foxboro/ICT model
Preparation of SH-IL-Pd catalysts
93). As the H pressure remained unchanged, the product was
2
collected via centrifugation (12000 rpm) and analyzed by a gas
The catalyst SH-IL-Pd containing 1.0 wt% Pd (denoted as SH-
IL-1.0%Pd) was prepared in the following way. 10.0 g of the
activated sepiolite (i.e., SH) was dispersed in 50 mL of aqueous
chromatograph (Agilent 4890 D) equipped with an Innovax cap-
illary column and a Varian FID-GC flame ionization detector.
The Heck reaction was performed as follows. Iodobenzene
+
-
solution containing 0.7 g of TMG TFA , and stirred for about
h. Then the sepiolite was separated via centrifugation, and
(
2.0 mmol), methyl acrylate (2.2 mmol), triethylamine (Et
3
N,
6
2
.4 mmol), and 2 mg of SH-IL-1.0wt%Pd composite were added
treated with fresh IL aqueous solution again. These procedures
were repeated three times. The sepiolite treated with IL aqueous
into a 7 mL stainless steel autoclave with a magnetic stirrer. Then
◦
◦
the reactor was sealed and placed in an air bath of 140 C. After
solution was dried at 105 C for 24 h and named SH-IL. 1.0 g
a desired reaction time, the autoclave was cooled by ice water.
The product was dissolved by N,N-dimethylformamide (DMF,
10.0 mL) and analyzed by GC-MS. Conversion was determined
from the amount of consumed iodobenzene. Bromobenzene
instead of iodobenzene was also used to test the activity of the
catalyst in the similar way.
of SH-IL was redispersed in 10.0 mL of H
2
PdCl
4
(1M PdCl
2
+
2
M HCl) aqueous solution with a concentration of 1.0 mg/mL.
◦
Then the clay was dried at 60 C under vacuum after the water
was removed via evaporation, and denoted as SH-IL-Pd . SH-
IL-Pd was hydrogenated with H at 150 C for 4 h, resulting in
2
+
2
+
◦
2
a composite, designated as SH-IL-1.0 wt%Pd, since the mass
content of Pd in the composite was 1.0 wt%, calculated on
Results and discussion
the basis of the amounts of the clay and the PdCl
2
used. The
catalyst containing 2.5 wt% Pd was synthesized following the
Characterization of the catalysts
+
-
same procedure, named SH-IL-2.5%Pd. Instead of TMG TFA ,
+
-
+
-
other ILs including TMG LA , TMG AA and TMG were also
used to prepare the Pd catalysts in the similar way.
Before being used as catalysts, SH, SH-IL, and SH-IL-Pd
were characterized in detail by means of different techniques,
including XPS, TG, SEM, TEM, ICP-AES, XRD, and N
sorption analysis.
2
The XPS analysis was used to detect the oxidation state of
all species in the composites. Fig. 1a shows the survey spectrum
of SH-IL-1.0wt%Pd, which indicates that no element Cl was
Characterization
TG measurements were performed on a thermal analyzer
◦
(
NETZSCH STA 409 PC/PG) with a heating rate of 3 C/min.
detectable, suggesting that PdCl
2
was completely converted
SEM examination was carried out on a scanning electron
microscope (JEOL, JSM-4300) operated in a high-vacuum mode
at 15 kV, which provided general textural information of the
samples. The SEM samples were sputter-coated with gold before
observation. TEM observation was performed on a transmission
electron microscope (JEOL, JEM 1011) at an operating voltage
of 100 kV, and the images were electronically captured using
a CCD camera. XPS data of the as-prepared samples were
obtained with an ESCALab220i-XL electron spectrometer from
VG Scientific using 300 W MgKa radiation. The base pressure
during the H reduction process. From Fig. 1a, it is obvious that
2
element N was present in the composites. Fig. 1b illustrates the N
1s spectrum, in which the peak centered at 400.6 eV is attributed
to N species bounding to =C and –C, which originated from the
cation of the IL, suggesting that IL existed in the composites.
Fig. 1c displays the XPS spectrum of Pd 3d. Compared to the
20
binding energy values of Pd 3d in pure palladium metal, both
the predominant peak at 335.2 eV and the deconvolved peak
0
at 340.8 eV are attributed to Pd species, and the peaks at
337.1 eV and 342.9 eV are assigned to the partially oxidized
palladium species, which may result from the slight oxidation
-
9
was about 3 ¥ 10 mbar. The binding energies were referenced
to the C 1s line at 284.8 eV from adventitious carbon. XRD was
performed on a X’PERT SW X-ray diffractometer operated at
0
0
of Pd . From XPS analysis, it can be deduced that the Pd
species are predominant in the composites. XPS analysis shows
that the Pd content on the surface of SH-IL-Pd was about
0.94%, which is almost identical with the initial quantities of
Pd (1.0 wt%), implying that the Pd nanoparticals were mainly
decorated on the surface of sepiolite. The loading content of Pd
3
0 kV and 100 mA with CuKa radiation. The loading content
of Pd in the catalysts was determined by ICP-AES (VISTA-
MPX). The nitrogen sorption analysis was performed on an
ASAP-2405N instrument at liquid nitrogen temperature.
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the TEM image also shows that the particle size distribution of
the particles located on the rods was very narrow.
The samples, SH, SH-IL, SH-IL-1.0wt%Pd, and SH-TMG,
were also examined by XRD analysis. It was shown that these
four samples exhibited almost identical XRD patterns, which
suggests that the sepiolite in SH-IL, SH-IL-Pd, and SH-TMG
retained its original structure without any damage. There is
no expansion or collapse of the sepiolite framework, which
suggests that no IL was impregnated into the channels of
sepiolite. This is different from our previous work, in which
the IL was intercalated into the interlayers of montmorillonite
16
and expanded them to some extent. In the pattern of SH-IL-
Pd, no detectable diffraction peak was assigned to Pd species in
the wide angle range, which indicates that there were no large
Pd particles in the SH-IL-Pd composites.
To verify the changes of the surface area and porous charac-
teristics of the sepiolite in SH-IL and SH-IL-Pd, the as-prepared
samples were evaluated by N sorption analysis. Fig. 3 shows the
2
corresponding isothermal curves of SH-IL-1.0wt%Pd, which
belongs to type IV sorption isotherms with hysteresis loop of
21
type H1 according to the IUPAC classification. The other
samples (e.g. SH, SH-IL, SH-IL-2.5wt%Pd) exhibited similar
sorption isotherms to the SH-IL-1.0wt%Pd composite, implying
the immobilization of IL and Pd nanoparticles did not destroy
the main structure of the sepiolite. The specific surface areas
of the samples were achieved by the BET method (Brunauer-
Emmett-Teller) in the relative pressure range of 0.05–0.20 from
22
nitrogen desorption isotherms, and the pore size distribution
was determined by the BJH method (Barrett-Joyner-Halenda).
2
The specific surface area of the clay decreased from 72.3 m /g
2
Fig. 1 XPS spectra of SH-IL-1.0wt%Pd: (a) survey spectrum, (b) N 1s,
c) Pd 3d.
for the sepiolite activated by nitric acid to 40.5 m /g for SH-IL
2
(
due to the immobilization of the IL, and further to 34.6 m /g
for SH-IL-Pd, which may result from the deposition of Pd
nanoparticles on the surface of sepiolite. The small hysteresis
of the composite indicates less mesoporosity present in the
in SH-IL-1.0wt%Pd was also determined by ICP-AES. It was
demonstrated that the Pd content was 0.95 wt%, nearly equal to
the value obtained from XPS analysis, further confirming that
the Pd nanoparticles were uniformly distributed on the sepiolite
support.
sepiolite. From the N sorption analysis, it is known that the total
2
pore volume is reduced from 0.13 mL/g for SH to 0.09 mL/g
for SH-IL composites, and to 0.07 mL/g for SH-IL-Pd, due
to the absorption of IL and the deposition of Pd nanoparticles.
Furthermore, the pore size distribution is much broader and has
no significant change after the deposition of Pd nanoparticles in
the composite.
To determine the loading content of IL on the sepiolite
support, TG analysis for SH and SH-IL was carried out from
◦
◦
-1
room temperature to 700 C at a heating rate of 3 C min . At
7
◦
00 C, the residual contents of SH and SH-IL were 92.8 wt%
and 91.2 wt%, respectively, which gives the information that the
IL was indeed immobilized on the sepiolite support, and the
loaded IL content was about 1.6 wt%.
The microstructure and morphology of the resultant com-
posites were examined by SEM and TEM. The SEM images of
SH-IL-1.0wt%Pd, as shown in Fig. 2, indicate that the sepiolite
exhibited fibrous structure with an average diameter of about
Catalytic activities for hydrogenations and Heck Reactions of
the catalysts
To evaluate their catalytic characteristics, the as-prepared SH-
IL-Pd composites were used to catalyze the hydrogenations of
some alkenes, including cyclohexene, 1-hexene, styrene and 1,3-
cyclohexdiene, at different conditions, and the results are listed
in Table 1. Both 1-hexene and styrene could almost completely
1
00 nm and length in the range from 20 nm to 2 mm. Some
fibers congregated into bundles, and a great deal of sepiolite
fibers stacked up, leading to pores with different sizes. The
TEM images provided more information about the morphology
of SH and SH-IL-1.0wt%Pd. Fig. 2c shows a typical TEM
image of SH, which indicates that sepiolite is composed of fibers
with smooth surfaces. For the SH-IL-1.0wt%Pd composite, the
surface of the fiber became rough, and there were numerous
nanoparticles attached along the fibers. It is clear that the
particle size was less than 5 nm, as shown in Fig. 2d; moreover,
convert into hexane and ethyl benzene within 0.5 h, respectively,
◦
at 60 C and initial H
2
pressure of 2 MPa with a substrate/Pd
molar ratio of 5000 (Table 1, entries 1 and 2). The conversion of
cyclohexene could approach 100% within 1 h with cyclohexane
as the only product under the same conditions (Table 1, entry 3).
The turnover frequencies (TOFs), defined as moles of substrate
consumed per mole of palladium per hour, could reach 10000
-
1
or 5000 h , suggesting that the SH-IL-Pd catalyst was very
9
8 | Green Chem., 2009, 11, 96–101
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Fig. 2 SEM images of SH (a), (b); and TEM images of SH (c) and SH-IL-Pd (d).
of sepiolite and no remarkable aggregation of Pd nanoparticles
occurred after the catalyst was reused for five times, as shown in
Fig. 4.
Fig. 4 TEM image of the SH-IL-1.0wt%Pd catalyst after it was reused
for five times for hydrogenation of cyclohexene.
Fig. 3 Nitrogen sorption isotherms (a) and pore size distribution
b) of SH-IL-1.0wt%Pd.
The SH-IL-1.0wt%Pd catalyst also exhibited a good activity
for cyclohexene hydrogenation at lower temperatures (e.g.,
Table 1, entries 8 and 9), but the TOFs decreased with decreasing
temperature. The influence of Pd content on the hydrogenation
was also investigated. For example, the SH-IL-2.5wt%Pd com-
posite was used to catalyze the hydrogenation of cyclohexene,
which displayed comparable activity with SH-IL-1.0wt%Pd at
(
active for these reactions. Taking the cyclohexene hydrogenation
as an example, the stability of the SH-IL-1.0wt%Pd catalyst
was investigated. It was demonstrated that there was almost
no activity loss after the catalyst was reused for five times
for this reaction (Table 1, entries 3–7), indicating that the as-
prepared catalyst was rather stable. TEM observation for the
five-time reused catalyst also support this, which shows that
the Pd nanoparticles were still firmly adhered on the surface
the C
However, this catalyst was less active than SH-IL-1.0%Pd when
the C 10/Pd molar ratio was 10000, as listed in Table 1 (entries
6
H10/Pd molar ratio of 5000, as shown in Table 1 (entry 11).
6
H
10 and 12). This might result from the slight increment of Pd
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a
Table 1 Results of catalyst performance in hydrogenations of alkenes
◦
TOF/h-1
Entry
Catalyst
Substrate
Substrate/Pd (mol/mol)
T/ C
P(H
2
)/MPa
Time/h
Conversion (%)
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-1.0%Pd
SH-IL-2.5%Pd
SH-IL-2.5%Pd
SH-IL-1.0%Pd
SH-IL-2.5%Pd
Pd/C, 5%Pd
1-Hexene
Styrene
5000
5000
5000
5000
5000
5000
5000
5000
5000
10000
5000
10000
5000
5000
5000
5000
60
60
60
60
60
60
60
40
20
60
60
60
60
60
60
60
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
0.5
0.5
1
1
1
1
1
2
6
2
1
2
3.5
0.5
0.5
1
>99.0
>99.0
>99.0
>99.0
>99.0
>99.0
>99.0
98.0
10000
10000
5000
5000
5000
5000
5000
2450
833
5000
5000
4400
1428
—
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
Cyclohexene
1,3-Cyclohexdiene
Cyclohexene
Cyclohexene
Cyclohexene
b
c
d
e
98.2
1
1
1
1
1
1
1
>99.0
>99.0
88.0
>99.0
95.0
80.2
>99.0
f
—
5000
g
SH-IL-1.0%Pd
a
b
c
The amount of cyclohexene was 12 mmol. SH-IL-1.0%Pd reused for the second time for cyclohexene hydrogenation. SH-IL-1.0%Pd reused for
d
e
the third time for cyclohexene hydrogenation.f SH-IL-1.0%Pd reused for the fourth time for cyclohexene hydrogenation SH-IL-1.0%Pd reused for
g
the fifth time for cyclohexene hydrogenation. The product is cyclohexene. The amount of cyclohexene was 100 mmol.
◦
particle size in the SH-IL-2.5%Pd composite. For comparison,
the commercially available catalyst Pd/C (5 wt%Pd) was used
to catalyze the cyclohexene hydrogenation. As shown in Table 1
at 140 C containing triethylamine (Et
3
N, 1.2 equiv) under
solvent-free conditions. The conversion of iodobenzene could
reach 100% within 65 min, and no production of biphenyl was
detected. This indicates that the catalyst had high efficiency for
this Heck reaction. However, as the reaction time was prolonged
from 65 min to 20 h, a little cinnamic acid was obtained,
which may result from ester hydrolysis of methyl cinnamate.
The stability of SH-IL-1.0wt%Pd for the Heck reaction of
iodobenzene with methyl acetate was examined by performing
this reaction for 5 consecutive runs, and no noticeable activity
loss was observed, suggesting that this catalyst was also stable
for the Heck reaction. Bromobenzene instead of iodobenzene
was investigated for Heck reaction under the same conditions.
Unfortunately, the catalyst displayed little activity for this
reaction.
To explore the scalability of the as-prepared SH-IL-Pd
catalyst, SH-IL-1.0%Pd was used to catalyze hydrogenation
of 100 mmol cyclohexene and Heck reaction of 16 mmol
iodobenzene with methyl acrylate, respectively. It was demon-
strated that the catalyst was still very effective for cyclohexene
hydrogenation as the amount of cyclohexene increased (as listed
in Table 1, entry 16), and it was also very active for Heck
reaction of iodobenzene and methyl acrylate with the increment
of iodobeneze.
(
entries 14 and 15), the catalyst prepared in this work was more
active than the Pd/C catalyst.
,3-Cyclohexdiene hydrogenation was selected to investigate
1
the activity of the catalyst SH-IL-1.0wt%Pd for selective hydro-
genation. It was demonstrated that the catalyst showed high
activity for the selective hydrogenation of 1,3-cyclohexdiene,
◦
and cyclohexene was the main product. For instance, at 60 C
and the initial H
ratio of 5000, the conversion of cyclohexdiene could reach
9% within 3.5 hours, and the selectivity for cyclohexene could
approach 97.6%. This phenomenon was similar to that reported
2
pressure of 2 MPa with a C
6
H
8
/Pd molar
9
15
previously, which originated from the properties of Pd metallic
nanoparticles. Alkadienes are much more strongly adsorbed by
the Pd nanoparticles than alkenes, which resulted in preferential
hydrogenation of the alkadiene to the alkene. Moreover, the
small size of the Pd nanopartilcles is also favorable in enhancing
the selectivity.
The Pd catalysts mediated with other ILs including
+
-
+
-
TMG LA , TMG AA and TMG, were also used to catalyze
cyclohexene hydrogenation. It was demonstrated that these
catalysts exhibited almost identical activity for this reaction,
suggesting that 1,1,3,3-tetramethylguanidine cation played a key
role in immobilizing the Pd nanoparticles on sepiolite.
Besides the catalyst for hydrogenation reactions, Pd is also
an active catalyst for Heck reactions. For example, Clark et al.
supported Pd nanoparticles on porous materials derived from
starch in acetone solution, and the resultant Pd catalysts ex-
hibited excellent activities for the Heck reaction of iodobenzene
with methyl acetate under microwave irradiation. In this work,
the catalytic activity of the SH-IL-1.0wt%Pd catalyst for Heck
reaction was investigated using the model reaction of iodoben-
zene and methyl acrylate to give methyl cinnamate. The reaction
of iodobenzene (1.0 equiv) and methyl acrylate (1.1 equiv) with
the molar ratio of iodobenzene/Pd = 10000 was performed
Conclusions
In summary, the sepiolite supported Pd catalysts were success-
fully prepared with the aid of ILs, and the as-prepared catalysts
exhibited very high efficiency for hydrogenations of alkenes and
Heck reaction of iodobenzene and methyl acrylate. Moreover,
these catalysts were very stable and could be reused without
activity loss. These catalysts combined the advantages of natural
clay and ILs, resulting in environmentally friendly materials,
which are expected to find promising applications in industrial
catalysis.
23
1
00 | Green Chem., 2009, 11, 96–101
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Acknowledgements
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