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The influence of halogen anions and N-ligands in CuXnN-ligands on the catalytic performance in oxidative carbonylation of methanol.

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Full Paper
Received: 6 August 2009
Revised: 21 November 2009
Accepted: 7 December 2009
Published online in Wiley Interscience: 22 January 2010
(www.interscience.com) DOI 10.1002/aoc.1618
The influence of halogen anions and N-ligands
in CuXn/N-ligands on the catalytic performance
in oxidative carbonylation of methanol
Wanling Moa,b , Hui Xionga,b , Jianglin Hua , Youming Nia
and Guangxing Lia,b∗
The catalytic properties of CuXn /N-ligands (X = Cl, Br and I; n = 1 or 2) in oxidative carbonylation of methanol were investigated.
It was found that the interaction of halogen anions, N-ligands and Cu (I) affected the catalytic performance of copper complex
catalyst in the reaction, especially iodide anion and 1,10-phenanthroline (Phen). When CuI/Phen was used as a catalyst, the
conversion of methanol was 42.6%, the selectivity to dimethyl carbonate was 99.2% and the TOF was 13.1 h−1 at an optimized
conditions: CuI/Phen 0.2 mol l−1 , 120 ◦ C, 2 h, 2.4 MPa, PCO /PO2 = 2:1. Compared with the plain CuI catalyst, the catalytic
activity of CuI/Phen increased about 36 times. When CuI/Phen catalyst was immobilized on polystyrene (PS), the heterogenized
catalyst, CuI/Phen–NH–PS, also exhibited very high catalytic activity in oxidative carbonylation. The CuI/Phen – NH – PS catalyst
remained its high catalytic activity even after seven recycles. The average weight loss of CuI/Phen – NH – PS after reaction was
c 2010 John Wiley & Sons,
less than 1.0%, and the leaching of copper was only about 0.15% in each recycling test. Copyright Ltd.
Keywords: copper halides; N-ligands; halogen effects; oxidative carbonylation; polystyrene-supported catalyst
Introduction
576
Transition metal complexes are frequently employed as important
catalysts in many catalytic reactions, especially in homogeneous
systems.[1 – 5] Although the effects of the halide ligands on the
catalytic performance of noble metal complexes, for example
Pd, Rh and Ir, have been a huge subject for publication in
the literature,[6,7] the influence of the halogen anions in the
common transition metal complexes, like Cu, Ni and Fe, on the
performance in homogeneous catalytic reaction has not been
carefully determined.
The carbonylation reaction catalyzed by transition metal
complex is a very important one, e.g. the synthesis of acetic
acid by carbonylation and synthesis of dimethyl carbonate (DMC)
by oxidative carbonylation of methanol.[8,9] In synthesis of DMC
by the carbonylation process, CuXn /Schiff base catalytic systems
have attracted much attention,[10,11] as would be expected for
a potential application in the commercial process. The influence
of monodentate N-ligands on the copper-catalyzed oxidative
carbonylation of methanol had been reported and the results
showed that 1-methylimidazole ligand was the best among a
number of monodentate N-ligands studied.[10] Dong showed
the catalytic activity of various copper halide catalysts in the
presence of various ionic liquids, and found that N-butylpyridinium
tetrafluoroborate ionic liquid was an efficient medium for synthesis
of DMC.[12] So far, the effects of halogen anions in those
copper compounds on the catalytic activity and the relationship
between halides and N-ligands in the complexes have not been
discussed in detail. Xia reported the catalytic performance of
cuprous halides coordinated with N-heterocyclic carbene in the
oxidative carbonylation of amino compounds, and successfully
developed an efficient copper N-heterocyclic carbene catalyst for
Appl. Organometal. Chem. 2010, 24, 576–580
the reactions.[13] However, the influence of the halogen anions on
the catalytic activity was also not discussed.
Hence, the objective of the current work is not only to investigate
the influence of halogen anions and N-ligands on the activity
of copper complex catalyst, but also to explore an improved
copper complex supported on polystyrene (PS) catalytic system
for oxidative carbonylation. To the best of our knowledge, the
positive effect of the combined halogen anions and N-ligands on
the catalytic activity of CuXn /N-ligands catalyst and long lifetime
for the supported copper complex catalyst, CuI/Phen–NH–PS, in
the reaction has not been reported so far.
Experimental
Materials and Equipment
N,N-dimethylformamide (DMF) was dried with CaH2 and distilled
before used. The chloromethylated polystyrene resin (PS–Cl), contained 17% chlorine and was crosslinked with 6% divinybenzene.
It was swelled for 48 h in DMF before used. The [CuX(Phen)]2
complexes (X = Cl, Br and I) were synthesized according to the
∗
Correspondence to: Guangxing Li, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, 430074 Wuhan, People’s
Repulic of China. E-mail: ligxabc@163.com
a School of Chemistry and Chemical Engineering, Huazhong University of Science
and Technology, Wuhan 430074, People’s Repulic of China
b Hubei Key Laboratory of Material Chemistry and Service Failure, Huazhong
University of Science and Technology, Wuhan 430074, People’s Repulic of
China
c 2010 John Wiley & Sons, Ltd.
Copyright The influence of halogen anions and N-ligands on catalytic performance
Table 1. The catalytic performance of various copper halide
compounds
Entry
Scheme 1. Preparation process of CuI/Phen–NH–PS catalyst.
procedures described in the literature.[14] The other reagents
were obtained from commercially available sources and used as
received. Infrared spectra were recorded as KBr pellets in the
range 4000–400 cm−1 on a Bruker Equinox 55 FT-IR spectrometer. The C, H and N elemental analyses (EA) were carried out
on a Vario ELIII instrument. X-ray photoelectron spectroscopy
(XPS) data were recorded on a Kratos XSAM-800 photoelectron
spectrometer. The Cu loading and leaching in the immobilized
catalyst were measured by atomic absorption (AAS) on a Perkin
Elemer AA-300 spectrometer. Thermogravimetric analysis (TGA)
was conducted on a Perkin Elemer TGA-7 instrument at a heating
rate of 10 ◦ C/min, under an argon atmosphere. GC analyses were
performed on an Agilent GC-1790 gas chromatograph equipped
with an HP-5 capillary column and an FID detector.
Preparation of CuI/Phen–NH–PS Catalyst
The CuI/Phen–NH–PS catalyst was prepared by the method shown
in Scheme 1. The preparation process of Phen–NH–PS, i.e. the
chloromethylated polystyrene-bound 1,10-phenanthroline, was
according to the procedures described in the literature.[15] In
an N2 atmosphere, the yellow-brown resin of Phen–NH–PS was
added to the solution of CuI (15.2 mmol) in methanol (100 ml)
and refluxed for 24 h under stirring. After the reaction, the resin
was separated by filtration. The obtained yellow-green resin was
washed thoroughly by methanol and dried at 80 ◦ C for 24 h in
vacuum.
The Catalytic Activity of Catalyst
The activity of all catalysts was evaluated according to the
procedures described in the literature.[11] The activity and
recyclability of the heterogenized catalyst CuI/Phen–NH–PS were
tested according to the similar procedures described in the
literature.[15] After the first run, the CuI/Phen–NH–PS catalyst
was filtered from the solution and employed again in successive
oxidative carbonylation under the same reaction conditions.
Conversion and selectivity were calculated by the following
equations:
nDMC + nMA
× 100%;
nMeOH
nDMC
× 100%
selectivity =
nDMC + nMA
conversion = 2 ×
where nDMC is the molar amount of the DMC, nMeOH is the molar
amount of the methanol and nMA is the molar amount of the
by-product methyl acetate.
Results and Discussion
Effect of Halogen Anions on the Catalytic Activity
Appl. Organometal. Chem. 2010, 24, 576–580
CuCl
CuBr
CuI
CuCl2
CuBr2
CDMC a
(%)
CMA b
(%)
ConvMeOH
(%)
SelDMC
(%)
TOF (h−1 )
8.8
13.0
1.6
9.0
12.9
0.27
0.38
–
0.57
0.89
6.4
9.8
1.2
6.9
10.5
96.4
96.6
>99.9
92.9
92.3
2.0
3.0
0.4
2.0
3.0
Reaction conditions: methanol 30 ml, CuXn 200 mmol l−1 , PCO /PO2 2:1,
2.4 MPa, 120 ◦ C, 2 h, stirring speed 1000 rpm. a Concentration of DMC;
b concentration of methyl acetate.
Table 1, show that the catalytic activity follows the order CuBr >
CuCl > CuI.
According to the proposed reaction mechanism for copper catalyzed oxidative carbonylation of methanol,[10,16,17] the formation
of monocarbonyl species CuClCO and the insertion of CO into
the copper–oxygen bond of the cupric methoxychlide are the
key steps in the catalytic cycle. It is well known that CO is an
excellent π acceptor, and the Cu–CO bonding is stabilized by
π back-bonding interaction between Cu and CO. The higher the
electron density on Cu, the more stable the Cu–CO bond. As the
electronegativity of Cl, Br and I is 3.0, 2.8, and 2.5, respectively,[14]
the electron density on Cu increases in the order CuCl < CuBr <
CuI and the stabilization of the Cu–CO bonding in CuXCO follows
the order CuClCO < CuBrCO < CuICO. These indicate that CuCl
is less reactive toward CO, and CuI is more attractive for CO than
that of CuBr. The Cu–CO bonding in CuClCO is labile, and the
Cu–CO bonding in CuICO is so stable that insertion of CO into
the copper–oxygen bond of the copper methoxide is difficult.
Therefore, it could be said that the electronegativity of Br is more
suitable for the formation of monocarbonyl species CuBrCO and
the insertion of CO into the copper–oxygen bond of the copper
methoxide than that of Cl and I. Hence, the catalytic activity of
CuBr is the best one among all of cuprous halides.
It is also shown in Table 1 that the catalytic activity of cupric
halides is almost as good as the corresponding cuprous halides,
even if the solubility of a cupric halide in methanol is much better
than that of the corresponding a cuprous halide.[12] These results
indicate that the influence of solubility of copper compounds in
methanol on the activity is small. In addition, when cuprous halide
was used as a catalyst, the selectivity to DMC was higher than that
of the corresponding cupric halide. In a study of DMC synthesis
using copper chloride catalyst by Romano, it was found that the
best catalyst was one with the chlorine-to-copper ratio was close
to 1 : 1.[16] This means that the ratio of halogen and copper in the
reaction affects the rate and the selectivity of DMC formation.
Effect of N-ligands on the Catalytic Activity
The role of the N-ligands in catalytic performance of CuXn /Nligands for synthesis of DMC has been studied, and the results
have been summarized in Table 2.
The results in Table 2 show that, when the N-ligands are introduced into the CuXn catalytic system, the catalytic activity follows
the order CuCl < CuBr < CuI, which is quite different from the order
of cuprous halides without any ligand. When 1-methylimidazole
(NMI) was used as a ligand, the catalytic performance of CuI was
c 2010 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
577
The influence of halogen anions on the activity of copper catalyst
in oxidative carbonylation has been investigated. The results, in
1
2
3
4
5
Catalyst
W. Mo et al.
Table 2. Effects of N-ligands on the catalytic activities
Entry
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Catalyst
CLigand (mol l−1 )
CDMC (%)
CMA (%)
ConvMeOH (%)
SelDMC (%)
TOF (h−1 )
CuCl/NMI
CuBr/NMI
CuI/NMI
CuCl2 /NMI
CuBr2 /NMI
CuCl/NH2 -Py
CuBr/NH2 -Py
CuI/NH2 -Py
CuCl2 / NH2 -Py
CuBr2 / NH2 -Py
CuCl/Phen
CuBr/Phen
CuI/Phen
CuCl2 /Phen
CuBr2 /Phen
[CuCl(phen)]2
[CuBr(phen)]2
[CuI(phen)]2
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.2
0.2
0.2
0.2
0.2
–
–
–
14.9
21.1
22.6
7.7
24.3
13.8
20.4
21.4
26.2
19.9
26.4
31.0
53.6
1.6
2.0
16.2
19.4
35.1
0.18
0.40
0.12
0.15
0.08
–
–
–
–
–
0.35
0.37
0.37
–
–
0.22
0.24
0.10
11.2
16.1
17.0
5.6
18.2
10.2
15.1
16.0
19.6
14.7
20.5
23.6
42.6
1.2
1.5
12.1
14.6
26.8
98.5
97.6
99.9
97.8
98.1
>99.9
>99.9
>99.9
>99.9
>99.9
98.4
98.6
99.2
>99.9
>99.9
98.4
98.5
99.7
3.4
4.9
5.2
1.7
5.5
3.2
4.7
5.0
6.1
4.6
6.3
7.2
13.1
0.4
0.5
3.6
4.5
8.2
Reaction conditions: methanol 30 ml, Cu 200 mmol l−1 , PCO /PO2 2:1, 2.4 MPa, 120 ◦ C, 2 h, stirring speed 1000 rpm; NMI: 1-methylimidazole; NH2 -Py:
2-aminopyridine.
Table 3. Catalytic activity of supported and unsupported catalysts
Entry
1
2
3
4
5
6
7
8
9
Catalysts
Wcatalyst a (g)
CCu b (mmol l−1 )
ConvMeOH (%)
SelDMC (%)
TOF (h−1 )
CuI
CuI/NH2 -Phen
CuI/Phen–NH–PS
Removed from no. 3
Removed from no. 4
Removed from no. 5
Removed from no. 6
Removed from no.7
Removed from no. 8
0.9306
1.8826
3.9124
3.8357
3.7911
3.7587
3.7305
3.7003
3.6668
162
162
171
165
161
158
156
154
151
0.6
19.8
17.4
18.6
19.9
20.8
20.5
19.6
19.4
95.9
99.9
99.1
99.0
99.6
99.2
99.4
99.5
99.0
0.1
5.0
4.2
4.7
5.0
5.4
5.3
5.2
5.2
Reaction conditions: methanol 30 ml, PCO /PO2 9:1, 3.0 MPa, 120 ◦ C, 3 h, stirring speed 1000 rpm. a The weight of solid catalyst used in the reaction;
b the concentration of copper in the slurry system; NH -Phen: 5-amino-1,10-phenanthroline.
2
578
enhanced extraordinarily, with a conversion of 17.0% (Table 2,
entry 3), which was increased about 13-fold compared with a plain
CuI catalyst (Table 1, entry 3). However, it was a little surprising
that NMI could not improve the catalytic activity of CuCl2 under
the same conditions. When NH2 –Py was used as a ligand, the
catalytic activity of all copper halides could be also significantly
improved, and no by-product was detected.
When Phen was used as a ligand, the catalytic performance of
cuprous halides was enhanced dramatically. Among all of catalysts
tested, the CuI/Phen catalyst had the highest catalytic activity, with
a conversion of 42.6% and selectivity 99.2% (Table 2, entry 13).
Compared with the plain CuI catalyst (Table 1, entry 3), the catalytic
activity of CuI/Phen catalyst increased about 36 times. These results
indicate that the combined halogen anions/N-ligands affected the
catalytic performance of CuXn /N-ligands catalyst significantly.
When the [CuX(Phen)]2 complex was used as a catalyst, the
catalytic activity was less than that of the corresponding CuX/Phen
catalyst (Table 2, entries 16–18 and 11–13). The results indicate
that, as the stable [CuX(Phen)]2 dimer formed, the coordination
www.interscience.wiley.com/journal/aoc
of CO, CH3 O− species with the Cu species in the complex was
retarded more or less; this would be the final effect on the reaction
rate.
Generally, N-ligands are both σ -donators and π -acceptors when
the ligands coordinate with transition metal ion to form complexes.
The greater the σ -donor ability is, the greater the π -acceptor
capacity is in the metal complexes.[18] When Cu coordinates
with N-ligands, the charge-transfer interaction between Cu
and the ligands may remarkably influence the electron density
together on the Cu. Munakata studied the reactivity of cuprous
complexes [CuXL]2 (X = Cl, Br, and I; L = 2,2 -bipyridine and
1,10-phenanthroline) with CO.[14] They suggested that the chargetransfer interaction between Cu (I) and 2,2 -bipyridine (bpy) was
markedly weakened upon the addition of CO, and consequently
CO competed with bpy concerning the interaction with Cu
(I) ion. Then, the bondings of Cu–L and Cu–CO are delicately
balanced by the halogen anions, and iodine anion as a ligand
is the best one among all of the halogens. Rodgers studied the
interactions between Cu (I) and N-donor ligands experimentally
c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 576–580
The influence of halogen anions and N-ligands on catalytic performance
and theoretically.[19] Their results demonstrated that the electron
density on Cu (I) of the complexes coordinating with Phen was
lower than that with pyridine. On these points, the interaction of
iodine anion, Phen and Cu (I) is the most suitable for the formation
of Cu–CO and the insertion of CO into the copper–oxygen bond
of the copper methoxide. Accordingly, the CuI/Phen catalyst
exhibites the highest catalytic activity among all of the CuXn /Nligands catalysts tested. Maitlis discussed the promotion effect of
iodide on homogenous carbonylation about Rh, Ir, Pd catalytic
systems in great detail.[6] They found that iodine anion could
dramatically increase the activity and they also proposed a
mechanism in terms of activation of substrates, promotion of
oxidative addition, reductive elimination and stabilization of low
oxidative states. However, there has been no report on the
promotion effect of iodine anion in CuXn /N-ligands system, just
as we found. Obviously, our observation is a good example of the
catalytic oxidative carbonylation system, although determining
the detail of this promotion effect mechanism is still a great
challenge for us.
Table 4. XPS data of CuI, Phen–NH–PS and CuI/Phen–NH–PS
Binding energy (eV)
Compound
CuI
Phen–NH–PS
CuI/Phen–NH–PS
CuI/Phen–NH–PSa
a
Cu2p
N1s
I3d
931.9
–
932.9, 934.6
932.9, 934.6
–
398.9
399.8
399.8
619.5
–
619.4
619.4
After seven uses of the CuI/Phen–NH–PS catalyst.
1610cm-1
(A)
(B)
Catalytic Properties of Heterogenized Catalyst CuI/
Phen–NH–PS
Although the activity and efficiency of CuI/Phen catalyst in this
homogeneous catalytic reaction is very high, the drawback is the
separation of the catalyst from the reaction medium, which makes
the reuse of the complex catalyst very difficult and increases
the operation cost in terms of industrial application. In order
to overcome this problem, the immobilization of the CuI/Phen
on the polystyrene by grafting is a good technical strategy. The
catalytic activity of the heterogenized catalyst CuI/Phen–NH–PS
was examined, and the results are summarized in Table 3.
It was found that CuI/Phen–NH–PS catalyst (Table 3, entry
6) was very active. The conversion of methanol, selectivity to
DMC and TOF were 20.8%, 99.2% and 5.4 h−1 , respectively. The
conversion was about 35 times higher than that of the plain CuI
catalyst (Table 3, entry 1), and was comparable to the activity of the
CuI/NH2 -Phen complex homogeneous catalytic system (Table 3,
entry 2) under the same reaction conditions. Heterogenized
catalysts often suffer from a decrease of the activity as an extensive
leaching of active metal species during reactions. In our case,
CuI/Phen–NH–PS catalyst could maintain its high catalytic activity
even after seven runs (Table 3, entries 3–9), and the average
weight loss of the CuI/Phen–NH–PS was only 0.98%. The average
leaching of Cu, which is the active constituent of the catalyst,
was around 0.15%. Compared with other heterogenized catalysts
used in the carbonylation of methanol to make DMC reported in
the literature,[15,20 – 23] CuI/Phen–NH–PS is a reusable and efficient
solid metal complex catalyst for the oxidative carbonylation of
methanol with high catalytic activity, long lifetime, easy separation
and low weight loss for each recycle.
Characterization of CuI/Phen–NH–PS Catalyst
Appl. Organometal. Chem. 2010, 24, 576–580
1606cm-1
3357cm-1
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber / cm-1
Figure 1. FT-IR spectra of Phen–NH–PS (A) and CuI/Phen–NH–PS catalyst
(B).
a red shift for the N–H bond and a blue shift for the stretching
vibrations of the C N double bond were caused by ferric ion.
Therefore, the FTIR data provided evidence for the existence of a
strong ligand interaction between the N–N bidentate ligand and
Cu (I) ion in CuI/Phen–NH–PS catalyst. In order to confirm the
coordination of Phen–NH–PS with Cu (I), XPS data of polymerbound Phen and its complex were compiled (Table 4).
It was found, as shown in Table 4, that the binding energy of
N1s in CuI/Phen–NH–PS was 399.8 eV, which was higher than that
in Phen–NH–PS. The difference of I3d binding energy between
CuI and CuI/Phen–NH–PS was 0.1 eV. The Cu2p photoelectron
transitions of the CuI/Phen–NH–PS catalyst were observed at
932.9 eV with a shoulder peak at 934.6 eV. The differences in
Cu2p binding energy between CuI/Phen–NH–PS and CuI were 1.0
and 2.7 eV, respectively. In oxidative carbonylation of methanol
catalyzed by poly(N-vinyl-2-pyrrolidone)-CuCl2 complex catalyst,
Hu[25] found that the chemical shifts of the binding energies of
Cu, N and Cl elements were induced by the coordination bonding
when Cu was immobilized on poly(N-vinyl-2-pyrrolidone) polymer.
Therefore, the XPS data of the CuI/Phen–NH–PS, Phen–NH–PS
and CuI indicate that the chelating state has occurred between
N and Cu atoms. Thus copper ions have been successfully
immobilized on the Phen–NH–PS support.
The XPS data of the CuI/Phen–NH–PS catalyst used seven
times are also compiled in Table 4. It shows that the binding
energies of Cu, N and I elements did not shift for the seventimes recycled CuI/Phen–NH–PS catalyst, compared with fresh
CuI/Phen–NH–PS catalyst.
c 2010 John Wiley & Sons, Ltd.
Copyright www.interscience.wiley.com/journal/aoc
579
The FTIR spectra of Phen–NH–PS and CuI/Phen–NH–PS catalyst
are shown in Fig. 1. A stretching vibration for the N–H bond
appears at 3396 cm−1 and the stretching vibrations of the C N
double bonds appears at 1610 cm−1 for Phen–NH–PS. The
stretching vibration for the N–H bond and the stretching vibrations
of the C N double bond appear at 3357 and 1606 cm−1 for
CuI/Phen–NH–PS, respectively. For the preparation of polymerbound Phen and its ferric ion complexes, Wang[24] reported that
3396cm-1
W. Mo et al.
leaching in each recycling catalytic reaction. Despite the promising
results, the mechanism of interaction of halogen anions, N-ligands
and active metal species in the complexes in the catalysis is still
very unclear at this stage, and the study on this line is underway in
our group.
100
TG (%)
80
Phen-NH-PS
60
CuI/Phen-NH-PS
Acknowledgments
We are thankful for the financial support given by the Research
Foundation of Faculty of Science, Huazhong University of Science
and Technology. We also thank the Analytical and Testing
Center, Huazhong University of Science and Technology, for the
spectroscopic analysis of the catalyst.
40
20
0
100
200
300
400
500
600
700
Temperature (°C)
Figure 2. TGA curves for Phen–NH–PS and CuI/Phen–NH–PS.
The contents of Cu, C, H and N in the CuCl/Phen-PS catalyst
were 8.33, 62.80, 4.28 and 5.51%, respectively, as determined
by AAS and EA. The concentrations of the active constituent Cu
8.33
(CCu = 63.55
× 100 ) and the ligand NH2 –Phen (CNH2 −Phen =
5.51
14.00 × 3 × 100 ) in the CuI/Phen–NH–PS catalyst were 1.31 and
1.31 mmol g−1 . Therefore, the molar ratio of Cu : NH2 -Phen in this
solid catalyst was 1 : 1. Taking into account the XPS and FTIR data,
the schematic model of the CuI/Phen–NH–PS catalyst proposed
in Scheme 1 would be reasonable.
In order to confirm the thermal stability of CuI/Phen–NH–PS
in reaction conditions, the TGA curves for Phen–NH–PS and
CuI/Phen–NH–PS are shown in Fig. 2. It was found that both
Phen–NH–PS and CuI/Phen–NH–PS are very stable even at
high temperatures. The thermal degradation of CuI/Phen–NH–PS
started at about 300 ◦ C. This means that the CuI/Phen–NH–PS
catalyst is stable at the reaction temperature in oxidative
carbonylation of methanol.
Conclusion
The catalytic properties of CuXn /N-ligands catalytic systems in
oxidative carbonylation of methanol were investigated. The results
indicated that the interaction of iodine anion, Phen and Cu
(I) could dramatically enhance the catalytic activity in the coppercatalyzed oxidative carbonylation of methanol. When the efficient
catalyst CuI/Phen was immobilized on polystyrene by grafting,
the heterogenized catalyst CuI/Phen–NH–PS also showed high
catalytic activity, long lifetime, easy separation as well as low
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