Cycloaddition reaction of propylene oxide and carbon dioxide over NaX zeolite supported metalloporphyrin catalysts

Article abstract of DOI:10.1007/s10562-014-1360-z

Metalloporphyrin catalysts has attracted extensive attention as the result of their outstanding biomimetic catalytic properties. In this paper, different kinds of unsupported (Co(TPP), MnIII(TPP)Cl and CoIII(TPP)Cl) and NaX zeolite supported metalloporphy

Full text of DOI:10.1007/s10562-014-1360-z

Catal Lett (2014) 144:1894–1899
DOI 10.1007/s10562-014-1360-z
Cycloaddition Reaction of Propylene Oxide and Carbon Dioxide
Over NaX Zeolite Supported Metalloporphyrin Catalysts
•
Fengyong Zhang Yujia Xie Pingle Liu
•
•
•
Fang Hao Zhengjie Yao He’an Luo
•
Received: 20 June 2014 / Accepted: 3 September 2014 / Published online: 14 September 2014
Ó Springer Science+Business Media New York 2014
Abstract Metalloporphyrin catalysts has attracted exten-
sive attention as the result of their outstanding biomimetic
catalytic properties. In this paper, different kinds of unsup-
ported (Co(TPP), MnIII(TPP)Cl and CoIII(TPP)Cl) and NaX
zeolite supported metalloporphyrin catalysts (Co(TPP)/NaX,
MnIII(TPP)Cl/NaX, CoIII(TPP)Cl/NaX) were prepared and
characterized. It has been found that these metalloporphyrin
catalysts showhighcatalyticactivity incycloaddition reaction
of propylene oxide and carbon dioxide under mild reaction
conditions. TheNaXsupportedmetalloporphyrincatalystsare
more stable and present better catalytic performance than the
unsupported metalloporphyrins. CoIII(TPP)Cl/NaX was bet-
ter than MnIII(TPP)Cl/NaX and CoTPP/NaX, the propylene
oxide conversion is 94.5 % and the selectivity to propylene
carbonate is 95.6 %.
for the motor, electronic and communication industry because
of their stable physico-chemical properties [7–9].
In the past decades, many different catalytic systems such
as alkali metal salts, ionic liquids, quaternary ammonium salts
and Schiff bases have been developed for the coupling reac-
tion [10–19]. But most of them suffer from harsh reaction
conditions and catalyst recycle [20–22]. As one of the elec-
tron-deficient compounds, metalloporphyrin have been used
as mild Lewis acids catalysts [23–26]. It has been reported by
many scholars that metalloporphyrins in conjunction with an
organic Lewis base such as 4-dimethylaminopyridine
(DMAP) or phenyltrimethylammonium tribromide (PTAT)
can reach a high yield of carbonate under mild reaction con-
dition [27–31]. However, the catalyst is difficult to be recy-
cled. Bai et al. choose magnetic ferriferrous oxide as support
to load metalloporphyrins and the yield of propylene car-
bonate only decreased by 3 % after several times recycle [32].
However, it is quite complex to prepare the catalyst. In this
paper, the catalyst was prepared by using NaX zeolite as
support to load metalloporphyrin [33–35], and it was applied
in the production of propylene carbonate by the cycloaddition
reaction of carbon dioxide and propylene oxide. The sup-
ported metalloporphyrin catalyst not only shows better cata-
lytic performance but also is easier to be recycled.
Keywords Supported-metalloporphyrin Á Cycloaddition
reaction Á Carbon dioxide Á Propylene carbonate
1 Introduction
Carbon dioxide generated from the burning of fossil fuels is
recognized as one of the greenhouse gases and major con-
tributor to the global warming problem [1]. Therefore, carbon
dioxide capture and utilization has attracted more and more
researchers’ attentions [2, 3]. One of the most promising
branches in this field is the synthesis of cyclic carbonates
[4] (Scheme 1). Propylene carbonate can be used as electro-
lyte, apolar aprotic solvent [5, 6] and useful polymer materials
2 Experimental
2.1 Catalytic Preparation
2.1.1 Materials
F. Zhang Á Y. Xie Á P. Liu (&) Á F. Hao Á Z. Yao Á H. Luo
College of Chemical Engineering, Xiangtan University,
Xiangtan 411105, China
Propylene oxide was distilled from CaH2. Propylene
epoxide and PTAT and DMAP were purchased from
Aldrich and used to reaction without further purification.
e-mail: liupingle@xtu.edu.cn
123

Cycloaddition Reaction of Propylene Oxide and Carbon Dioxide
1895
O
The amount of M(Cl)PP/NaX (M = Co and Mn) per
gram of the support was measured by Inductively Coupled
Plasma Atomic Emission Spectometer (IRIS Intrepid II
XSP ICP-AES) (Thermo Electron Co.) under a microwave
pressure digestion (MDS 200; CEM) with hydrofluoric and
aquaregia.
O
Cat
O
O
+
CO2
Scheme 1 Cycloaddition reaction of propylene oxide and carbon
dioxide
2.1.2 5,10,15,20-meso-Tetrametalloporphyrin
Complexes(M(X)TPP)
2.3 Procedure for the Catalytic test
Cycloaddition reaction of propylene epoxide and carbon
dioxide was carried out in a 50 ml stainless-steel autoclave
reactor with a Teflon liner and a magnetic stirrer. Typi-
cally, the catalyst (0.11 mmol), epoxide (100 mmol), and
co-catalyst (0.22 mmol) were added into the autoclave
reactor. And the reactor was then pressurized with the
appropriate amount of CO2 and heated to the setting tem-
perature. After the reaction, it was cooled in an ice bath.
The reaction mixture was separated by refrigerated cen-
trifugation. The reaction product was taken out and ana-
lyzed with gas chromatograph. The catalysts at the bottom
of centrifuge tube were washed with ethanol and dried for
12 h for recycle in the next reaction.
H2TPP was prepared according to the following procedures
[36, 37]. Co(TPP), MnIII(TPP)Cl and CoIII(TPP)Cl were
synthesized and purified by referring to the following pro-
cedures [36]. H2TPP was dissolved in DMF and the solution
was heated to reflux with stirring. Then, cobalt acetate or
manganous acetate was added in three portions within
30 min. When the thin-layer chromatography (silica) indi-
cated no free base porphyrin, the solution was cooled to
70 °C, and then 40 mL of 6 M HCl was added and stirred for
4 h. The solution was cooled and the appeared solid was
filtrated and washed with 3 M HCl until the filtrate no longer
appeared red. The obtained solid was vacuum-dried, and it
gave 85–98 % yield of M(Cl)TPP (Co(Cl)TPP, Mn(Cl)TPP).
2.1.3 Preparation of M(Cl)TPP/NaX
3 Results and Discussions
The M(Cl)TPP/NaX was prepared by referring to the fol-
lowing procedures. A certain amount of M(Cl)TPP was
dissolved in toluene. The NaX zeolite was activated at
280 °C and added into the solvent. The mixture was heated
to reflux with stirring for 10 h. After evaporating a large
amount of the solvent and the mixture was vacuum dried
for 12 h. The unsupported metalloporphyrin was washed
away by toluene. The loading amount of metalloporphyrin
was determined by ICP element analysis.
3.1 Characterization of Catalysts
UV–Vis was used to confirm the formation of cobalt and
manganese porphyrin. The results of UV–Vis absorption of
M(Cl)TPP and MTPP were shown in Fig. 1. There is an
obvious peak at the wavelength around 400 nm and more
than one peaks at the wavelength exceed 500 nm, which is
in accordance with the theory that there is one Soret band
and more than one Q band in the ultraviolet visible region
2.2 Catalysts Characterization
UV–Vis spectra was obtained by UV-2550 spectropho-
tometry with a scan range of 300–800 nm for metallopor-
phyrins chloride complexes using 1 cm quartz cuvette.
M(Cl)PP/NaX was characterized by using barium sulphate
as reference, a small amount of BaSO4 was pressed into a
thin pellets, and some samples were put on the pellets and
pressed again, then it was used to assay the spectra.
TG-DTG curves were carried out on a TGA Q50 using
air as purge gas (80 mL min-1). The temperature is
between 30 and 900°Cwith a heating rate of 10 °C/min.
X-ray diffraction (XRD) patterns were collected on a
Japan Rigaku D/Max 2550 VB ? 18 kW X-ray diffrac-
tometer under the conditions of 40 kV, 30 mA, Cu Ka
radiation. It was performed in the range of 2h = 5–35° at a
scanning rate of 2°/min.
Fig. 1 UV–Vis spectra of different kinds of metalloporphyrin
123

1896
F. Zhang et al.
Fig. 4 TG-DTG for Co(Cl)TPP/NaX powder
Fig. 2 UV–Vis spectra of NaX and NaX supported metalloporphyrin
Fig. 5 TG-DTG for Mn(Cl)TPP/NaX powder
Thermal analysis was conducted to confirm the stability
of the supported catalysts during the reaction. The results
has been shown in Figs. 4, 5 and 6. The metalloporphyrins
have a rapid weight loss between 400 and 600 °C and the
structure is destroyed. A rapid weight loss between 60 and
200 °C in the supported metalloporphyrins is related to the
adsorbed water and some impurities, such as free ligand,
pyrrol etc. [38].
Fig. 3 XRD patterns of NaX and NaX supported metalloporphyrin
of porphyrin. With the addition of metal, the symmetry of
the porphyrin molecular structure will increase. As a result,
the Q band will reduce to one or two.
UV–Vis spectra of the metalloporphyrins supported on
NaX zeolite are shown in Fig. 2. All the supported
metalloporphyrins have the Soret peak between 400 nm
and 500 nm. Mn(Cl)TPP/NaX presents adsorption peak at
570 and 720 nm. As to NaX support, there are no obvious
adsorption peaks between 400 and 600 nm. The UV–Vis
spectra indicates that the metalloporphyrins have been
successfully supported on NaX zeolite.
The loading amount of metalloporphyrins on the support
was determined by Inductively Coupled Plasma Atomic
Emission Spectometer (IRIS Intrepid II XSP ICP-AES).
The results show that the amount of Co(Cl)TPP, CoTPP
and Mn(Cl)TPP was 80, 75 and 200 mg per gram of NaX
zeolite respectively.
The XRD patterns of NaX, Mn(Cl)TPP/NaX, Co(Cl)TPP/
NaX, CoTPP/NaX are shown in Fig. 3. All of them exhibit
characteristic broad peaks of the NaX molecular zeolite, and
it indicates that metalloporphyrins particles are well dis-
persed on NaX zeolite.
3.2 Catalytic Performance
The results of catalytic performance of different kinds of
unsupported metalloporphyrins are shown in Table 1.
123

Cycloaddition Reaction of Propylene Oxide and Carbon Dioxide
1897
Table 2 Results of cycloaddition of CO2 and PO catalyzed by sup-
ported metalloporphyrins
Entry
Catalysts
Conversion
Selectivity
Yield
1
2
3
Co(Cl)TPP/NaX
Mn(Cl)TPP/NaX
CoTPP/NaX
94.5
87.3
89.1
95.6
96.8
89.3
90.4
84.6
79.7
Reaction conditions: propylene oxide (100 mmol), catalysts (1.0 g,
active component 0.11 mmol), co-catalyst (0.22 mmol), 120 °C for
5 h, carbon dioxide pressure (3 MPa), pumped once
3.3 Possible Reaction Mechanism
Fig. 6 TG-DTG for CoTPP/NaX powder
It has been proved by Lu et al. [7, 41], Paddock et al. [27,
42] and Jing et al. [10] that both Lewis acid center and
Lewis base are necessary in the cycloaddition of propylene
oxide and carbon dioxide. In this paper, a possible mech-
anism for the reaction was proposed as follow (Scheme 2).
After loaded on the surface of NaX zeolite, the axial
ligand of metalloporphyrin will be removed from previous
location in order to provide a Lewis acid center (b and c)
for the incoming NaX zeolite and propylene epoxide. At
the same time, the hydroxy of NaX zeolite will help to
activate the oxygen ion of propylene epoxide. The acti-
vated propylene epoxide will be transferred to metallo-
porphyrin. With the addition of PTAT, Br-3 will attack
propylene epoxide and form an intermediate product d. The
insertion of carbon dioxide occurs after the ring opening of
d and produces e. After that, a stable five-membered ring
product propylene carbonate f has been obtained. The
leaving of Br-3 indicates the end of this circulation and the
beginning of the next reaction.
Table 1 Results of cycloaddition of CO2 and PO catalyzed by
metalloporphyrin
Entry
Catalysts
Conversion
Selectivity
Yield
1
2
3
Co(Cl)TPP
Mn(Cl)TPP
CoTPP
88.9
74.1
77.3
97.1
90.0
90.3
86.3
66.7
69.8
Reaction conditions: propylene oxide (100 mmol), catalysts
(0.11 mmol), co-catalyst (0.22 mmol), 30 °C for 3 h, carbon dioxide
pressure (3 MPa), pumped once
Compared with the Mn(Cl)TPP and CoTPP, the Co(Cl)TPP
exhibits the best catalytic performance under the same
reaction conditions. The conversion of PO is 88.9 % and
the selectivity to PC is 97.1 %. Compared with the
Co(II)porphyin and Mn(III)porphyin, the Co(III)porphyin
is a more electrophilic complex [27, 39] and thus has the
trendency to form electrom-donor center which will
accelerate the nucleophilic ring open of propylene oxide
[38]. As a co-catalyst, on one hand, PTAT is necessary for
the formation of a more electron-rich Co(III) center which
can help to activate the carbon dioxide in the Co(III)por-
phyin-PTAT system [38]. On the other hand, the easier
leaving group of Br-3 of PTAT will result in the separation
of propylene carbonate from the catalyst which contributes
to a better catalytic performance [29].
3.4 The Optimization of Reaction Conditions
The influence of temperature and reaction time were
studied and the results are shown in Fig. 7 and Fig. 8. The
yield of PC grows sharply from 11.2 to 90.4 % with the
increasing of temperature. But this phenomenon was ter-
minated when the temperature went up to 140 °C. As to the
supported catalysts, metalloporphyrins are dispersed on the
support uniformly, however it is more difficult to activate
propylene epoxide and carbon dioxide. Thus it is necessary
to raise the reaction temperature so as to provide enough
energy to activate the substrate and ensure the smoothly
running of the reaction. Since the cycloaddition reaction of
PO and carbon dioxide is an exothermic process, extra heat
will hinder the proceed of the reaction. It has been tested
that the best reaction temperature is 120 °C in this
Co(Cl)TPP/NaX catalyst system.
We can see from Table 2 that the catalytic performance
of supported metalloporphyrins was better than the
unsupported catalysts. The conversion of PO is 94.5 % and
the selectivity to PC is 95.6 %. We attribute this phe-
nomenon to the site isolation of immobilized complexes
which was caused by the unsupported metalloporphyrins’
partly accumulation during the reaction [40]. Furthermore,
the special structure of NaX and better adsorption capacity
of carbon dioxide on NaX zeolite may contribute to the
delightful result.
As to the unsupported metalloporphyrins, the yield of
PC reaches the maximum value when the reaction time is
123

1898
F. Zhang et al.
Scheme 2 Monometallic
mechanism for the reaction of
propylene oxide and carbon
dioxide
Fig. 8 The influence of reaction time on the results
Fig. 7 The influence of temperature on the reaction results
about 3 h. Because the number of activated molecular is
abundant, Co(Cl)TPP/NaX system costs 5 h to obtain the
maximum yield 90.4 % of PC, but the performance
decreased when we extend the reaction time to 6 h.
When we conducted our experiment without metallo-
porphyrins, that is the cycloaddition reaction of PO and
carbon dioxide was catalyzed by NaX/PTAT, the yield of
123

Cycloaddition Reaction of Propylene Oxide and Carbon Dioxide
1899
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Catalysts
Entry
Conversion
Selectivity
Yield
1
94.5
93.3
88.8
92.2
95.6
96.2
89.8
93.9
90.4
89.8
79.8
86.7
Co(Cl)TPP/NaX
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Average
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Different kinds of unsupported and supported metallopor-
phyrins were prepared and characterized. NaX zeolite
supported metalloporphyrin catalysts show better catalytic
performance than unsupported catalysts. The yield of PC is
improved more than 4 %. Co(Cl)TPP/NaX presents the
best results, it gives the selectivity to PC of 95.6 % at the
PO conversion of 94.5 %. This complex may be an active
and reusable catalyst for industrial cycloaddition process of
propylene oxide and carbon dioxide.
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Acknowledgments This
work
was
supported
by
the
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NSFC(21276218), SRFDP(20124301110007), Scientific Research
Fund of Hunan provincial Education Department (13K043,
CX2012B271) and the Project of Hunan provincial Science &
Technology Department (2012FJ1001).
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