Efficient Catalytic System Involving Molybdenyl Acetylacetonate and Immobilized Tributylammonium Chloride for the Direct Synthesis of Cyclic Carbonates from Carbon Dioxide and Olefins

Article abstract of DOI:10.1007/s10562-017-2020-x

Abstract: An effective direct method for preparing of cyclic carbonates from CO₂ and olefins in the presence of tert-butyl hydroperoxide as an oxidant was provided. The first stage, the epoxidation of olefins, was carried out using MoO₂(acac)₂ as a catalyst (1h, 100 °C), and the second stage, the cycloaddition of CO₂ to the resulting epoxide, was proceeded in the presence of immobilized tributylmethylammonium chloride on a polystyrene cross-linked with divinylbenzene, and an aqueous solution of ZnBr₂ (100 °C, 0.9?MPa of CO₂, 4?h). The proposed method allowed to obtain cyclic carbonates with high yields (50–77%) under mild conditions. Moreover, the immobilized catalyst could be reused at least five times without significant loss of its catalytic activity.

Full text of DOI:10.1007/s10562-017-2020-x

Catal Lett (2017) 147:1567–1573
DOI 10.1007/s10562-017-2020-x
Efficient Catalytic System Involving Molybdenyl Acetylacetonate
and Immobilized Tributylammonium Chloride for the Direct
Synthesis of Cyclic Carbonates from Carbon Dioxide and Olefins
1
1
1
1
Agnieszka Siewniak · Katarzyna Jasiak‑Jaroń · Łukasz Kotyrba · Stefan Baj
Received: 1 January 2017 / Accepted: 4 March 2017 / Published online: 29 March 2017
©
The Author(s) 2017. This article is an open access publication
Abstract An effective direct method for preparing of
1 Introduction
cyclic carbonates from CO and olefins in the presence of
2
tert-butyl hydroperoxide as an oxidant was provided. The
first stage, the epoxidation of olefins, was carried out using
MoO (acac) as a catalyst (1h, 100°C), and the second
Inexpensive, readily available carbon dioxide plays an
important role as a renewable raw material in several
industrial processes. Among them, the synthesis of cyclic
carbonates is of particular interest. The demand for cyclic
carbonates continues to grow due to the wide range of
their applications. They are used for polymer production
e.g. non-isocyanate polyurethanes, polycarbonates; and as
important intermediates in many processes for the prepara-
tion of fine chemicals. They are also employed as solvents,
and components of electrolytes for lithium-ion batteries
[1–4].
2
2
stage, the cycloaddition of CO to the resulting epoxide,
2
was proceeded in the presence of immobilized tributyl-
methylammonium chloride on a polystyrene cross-linked
with divinylbenzene, and an aqueous solution of ZnBr
2
(
100°C, 0.9 MPa of CO , 4 h). The proposed method
2
allowed to obtain cyclic carbonates with high yields (50–
7
7%) under mild conditions. Moreover, the immobilized
catalyst could be reused at least five times without signifi-
cant loss of its catalytic activity.
An important industrial method for preparing cyclic car-
bonate is by reaction of CO with epoxides [5]. However,
2
Graphical Abstract
it is possible to carry out their synthesis from olefins and
CO . This method involves two stages: the epoxidation of
2
olefins and the cycloaddition of CO to the resulting epox-
2
ide. Due to the fact there is no need to isolate the epoxide,
and the olefins are cheaper feedstock than epoxides, this
method can be advantageous from an economic and envi-
ronmental point of view. Although, the first report on this
reaction appeared in 1962 [6], it has not yet been imple-
mented on an industrial scale.
Keywords Carbon dioxide · Cyclic carbonates ·
Immobilization · Epoxidation · Cycloaddition
The direct synthesis of cyclic carbonates from carbon
dioxide and olefins is typically conducted at tempera-
ture 30–150°C and under pressure of CO in the range
2
Electronic supplementary material The online version of this
article (doi:10.1007/s10562-017-2020-x) contains supplementary
material, which is available to authorized users.
of 1–15 MPa. Among others, metals, metal oxides, metal
complexes, quaternary onium salts, and ionic liquids,
are used as catalysts. Oxygen, hydrogen peroxide, alkyl
hydroperoxides and urea hydroperoxide are usually used as
oxidizing agents in the epoxidation stage [7, 8].
*
Agnieszka Siewniak
agnieszka.siewniak@polsl.pl
1
The synthesis of cyclic carbonates using alkyl hydrop-
eroxides as oxidands is carried out mainly in the presence
of metals, ionic liquids, and quaternary onium salts as
Department of Chemical Organic Technology
and Petrochemistry, Faculty of Chemistry, Silesian University
of Technology, Krzywoustego 4, 44-100 Gliwice, Poland
Vol.:(0
1
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3

1
568
A. Siewniak et al.
catalysts. Conducting the reaction using tert-butyl hydrop-
eroxide (TBHP) as an oxidant and titanosilicate molecu-
lar sieves (TiMCM-41) and N,N-dimethylaminopyridine
as a catalyst system in acetonitrile as a solvent, allowed to
achieve conversion of olefin to epoxide only in the range of
of TBHP as an oxidant [18]. Use of mild reaction condi-
tions (50°C, 0.5 MPa) but long reaction times (96 h)
allowed for the preparation of cyclic carbonates with yields
in the range 72–92% and the enantioselectivity of 55–80%.
The catalyst could be used three times without a significant
reduction in its activity. Gosh et al. used the catalyst sys-
tem consisting of a manganese(III) complex of an amido-
amine ligand and TBAB for direct synthesis of cyclic
carbonates [19]. The yields in the range of 10–48% were
obtained under the reaction conditions: 100°C, 250 psig of
1
3–44%, and 97–100% conversion of the resulting epoxide
to cyclic carbonate with selectivities in the range 83–100%
[
(
9]. Arai et al. reported the synthesis of styrene carbonate
SC) from styrene (ST), TBHP and CO using ionic liquids
2
based on 1-n-alkyl-3-methylimidazolium or tetrabutylam-
monium cation as catalysts [10, 11]. The most effective
catalyst was tetrabutylammonium bromide (TBAB), how-
ever, SC was obtained only in 38% yield (reaction condi-
CO , using acetonitrile as a solvent. Cyclic carbonates can
2
be obtained with a selectivity of 44–68% at a conversion
of olefin in the range of 62–98.5% using mesoporous tita-
nium-silicate catalyst and TBAB as a cocatalyst [20]. The
tions: 80°C, a CO pressure of 1 MPa). In 2005, the same
2
group developed a method for preparation styrene carbon-
ate, in which a silica-supported gold catalyst was used for
the epoxidation of styrene with cumene hydroperoxide
reaction conditions were relatively mild: 50–70°C, a CO
2
pressure of 0.8 MPa, but the reaction time was 48 h.
The problems in above methods are usually not only
unsatisfying yields of cyclic carbonates and low selectivi-
ties, but also long reaction time, often not easy synthesis of
catalysts and their high price as well as difficulties associ-
ated with separation of the catalyst system and the inability
to its reuse. It should also be emphasized that most of the
described methods concerns only the synthesis of styrene
carbonate.
(
CHP) or TBHP, while ZnBr and TBAB were applied for
2
the second stage of the process [12]. The reaction was car-
ried out at the temperature of 80°C and under the pressure
of 1 MPa. The highest yield that has been achieved for sty-
rene carbonate was 45%. Sun and co-workers proposed the
catalyst system consisting of Au supported on Fe(OH) ,
3
ZnBr and TBAB for the synthesis of styrene carbonate
2
using CHP as an oxidant [13]. Under reaction conditions
Herein, we report an efficient one-pot procedure for the
of 80°C, a CO pressure of 4 MPa, styrene carbonate
synthesis of cyclic carbonates directly from CO and olefins
2
2
was obtained in yield of 53% after 10 h. In turn, the use
of gold (0.01 wt%) supported on R201 resin functional-
ized with quaternary ammonium functional groups allowed
to obtain styrene carbonate in 51% yield [14]. The reac-
tion selectivity was 52%. Styrene carbonate can also be
obtained in the reaction conducted in the presence of the
MoO (acac) , TBAB catalytic system and TBHP as an oxi-
using tert-butyl hydroperoxide as an oxidant. According to
our previous studies, the reaction of CO with epoxides
2
could be carried out with high selectivities and yields in the
presence of the catalyst system consisting of an immobi-
lized quaternary ammonium salt on a polymeric carrier and
an aqueous solution of zinc bromide(II) [21]. Therefore,
this catalyst system was used for the second stage of the
2
2
dant [15]. The styrene epoxidation reaction was carried out
for 1 h at the temperature of 100°C. Next, the reaction of
the resulting styrene oxide with carbon dioxide was con-
reaction of CO with olefins, while molybdenyl acetylace-
2
tonate (MoO (acac) ) was used as a catalyst for epoxidation
2
2
of olefins.
ducted for 1 h (140°C, CO pressure of 3 MPa). SC was
2
obtained in 68% yield whereas yields of other cyclic car-
bonates was in the range from 45 to 84%. 44% selectivity to
SC at 57% styrene conversion was achieved in the reaction
conducted with chromium-organic frameworks and TBAB
as a catalyst system, at temperatures of 25–100°C and a
2 Experimental
2.1 Chemical and Materials
CO pressure of 8–100 bar [16]. The ionic liquid 1-butyl-
Carbon dioxide (99.5%, from SIAD) was used with-
2
3
-methylimidazolium bromide was used in a one-pot reac-
out
further
purification.
Bis(acetylacetonato)
tion (150°C, 0.5 MPa of CO , 6 h) allowed to obtain SC
dioxomolybdenum(VI)
(molybdenyl acetylacetonate,
2
with 40% selectivity at 90% conversion of styrene, whereas
SC was obtained with a selectivity of 63% at 99% conver-
sion of styrene in the reaction conducted in a single reac-
tor under different conditions for each step (epoxidation
step: 100°C, 16 h, cycloaddition step: 150°C, 0.5 MPa,
MoO (acac) ), styrene (99%), styrene oxide (>97%), tribu-
2 2
tylamine (99%) were provided by Acros Organic. (Chloro-
methyl)ethylene carbonate, cyclohexene (99%), cyclohex-
ene oxide (98%), 1-octene (98%), octane (>99%), ~5.5 M
solution of tert-butyl hydroperoxide (TBHP) in decane,
were purchased from Sigma Aldrich. Epichlorohydrin
(>99%), tributylmethylammonium chloride (TBMAC)
and tributylmethylammonium chloride polymer bound
6
h) [17]. Recently, polyoxometalate-based homochiral
metal–organic frameworks were used as catalysts for enan-
tioselective synthesis of cyclic carbonates in the presence
1
3

Efficient Catalytic System Involving Molybdenyl Acetylacetonate and Immobilized…
1569
(
PS-TBMAC, 200–400 mesh; Cl loading: 1.2 mmol/g, pol-
The reactor was sealed and the reaction mixture was stirred
(500 rpm) and heated up to 100°C. After 1 h, the autoclave
was filled with carbon dioxide to the appropriate pressure
(0.9 MPa) and reaction was conducted for 4 h. Procedure
ystyrene 1% cross-linked with DVB) were obtained from
Fluka. Zinc bromide(II) (>98%) was bought from POCH
S.A.
3
: An olefin (58 mmol), MoO (acac) (0.058 mmol), TBHP
2 2
2
.2 Instrumentation
(64 mmol), an internal standard (0.4 g octane, or nonane,
depending on the olefin used in the process) were added
into an autoclave. The reactor was sealed and the reaction
mixture was stirred (500 rpm) at 100°C for 1 h. After com-
pletion of the first stage of the process, the reactor content
was cooled to room temperature. Then, the catalyst system
required to carry out the second stage of the process, con-
sisting of PS-TBMAC (0.58 mmol) and an aqueous solu-
tion of ZnBr (0.80 mmol of H O, 0.16 mmol of ZnBr ),
The pressure reactions were carried out in 100 ml auto-
clave (EM-60-100-SS-HC) placed in a solid-state thermo-
stat (EasyMax™ 102, Mettler Toledo). The pressure reac-
tor was equipped with a mechanical stirrer (pitched-blade),
temperature and pressure sensors and a rapture disc. Sam-
ples were analyzed by gas chromatography using Perki-
nElmer Clarus 500 chromatograph equipped with a flame
ionization detector (FID) and a capillary column (SPB-
2
2
2
was added. The reaction mixture was again heated up to the
desired temperature (90–130°C). After stabilization of the
temperature, the autoclave was filled with carbon dioxide
to the appropriate pressure (0.5–2.0 MPa) and reaction was
conducted for 4 h. Product isolation: After the completion
of the reaction, the mixture was cooled to room temperature
and filtered to remove PS-TBMAC. The filtrate was con-
centrated and then extracted with ethanol (3×5 ml) in order
to remove MoO (acac) which precipitated out as a solid.
5
™: 30 m×0.25 mm×0.25 μm film thickness). GC-MS
analyses were performed on a gas chromatography-mass
spectrometry system (Agilent Technologies 7890 A GC
system, Agilent Technologies 5975 C inert XL EI/CI MS
System) equipped with a capillary column (HP5/MS-5:
3
0 m×0.25 mm×0.25 μm film thickness). Octane or non-
ane were used as the internal standards for the quantifica-
tion of the formation of the products. The conditions of
MS analysis were as follows: EI, ionization voltage 70 eV,
ion source temperature 230°C, m/z range 33–550. NMR
spectra were recorded using a Varian 600 or 400 MHz
2
2
The organic phase was dried over anhydrous MgSO and
4
concentrated under reduced pressure. The crude product
was purified by column chromatography (hexane/chloro-
form). GC Analysis: On completion the reaction was cooled
to room temperature and the excess carbon dioxide was
vented. Then, the reaction mixture was diluted with 5 ml of
ethyl acetate and sample of the reaction mixture (5 µl) was
taken, dissolved in ethyl acetate (900 µl), and analyzed by
gas chromatography. Catalyst reusability: After the com-
pletion of the reaction, the immobilized catalyst was sim-
ply recovered by filtration, washed with dichloromethane
1
13
for H NMR and 150 or 100.6 MHz C NMR. Elemen-
tary analyses were performed on a PerkinElmer 2400
series 2 CHNO/S analyzer. Infrared spectroscopy (IR)
was conducted on a FT-IR spectrometer Mettler-Toledo
IC10 with ATR probe. The parameters of the FT-IR spec-
−
1
trometer: measuring range: 4000–650 cm , resolution: 4,
−
1
8
or 16 cm , operating temperature range: from −80 to
200°C.
+
(
6×5 ml). The filtrate was extracted with ethanol (3×5 ml)
2
.3 General Procedure of Cyclic Carbonates Synthesis
in order to extract MoO (acac) . The separated PS-TBMAC
2 2
during the filtration was dried in vacuum and then reused
for the next run.
Procedure An olefin (58 mmol), MoO (acac)
1
2
2
(
(
0.058 mmol), TBHP (64 mmol), PS-TBMAC
0.58 mmol), an aqueous solution of ZnBr (0.80 mmol
2
of H O, 0.16 mmol of ZnBr ), and an internal standard
2
2
(
0.4 g octane, or nonane, depending on the olefin used in
3 Results and Discussion
the process) were added into an autoclave. The reactor was
sealed and purged two times with carbon dioxide. Then, the
reaction mixture was stirred (500 rpm) and heated up to
The research was conducted on the example of a model
reaction between styrene and carbon dioxide (Fig. 1). The
first stage of the process, the epoxidation of styrene with
5.5 M solution of tert-butyl hydroperoxide in decane, was
conducted in the presence of MoO (acac) as a catalyst.
1
00°C. After stabilization of the temperature, the autoclave
was filled with carbon dioxide to the appropriate pressure
0.5–2.0 MPa). Process was conducted for 5 h. Procedure
: An olefin (58 mmol), MoO (acac) (0.058 mmol), TBHP
(
2
2
2
Based on our previous results [21], for the second step,
2
2
(
64 mmol), PS-TBMAC (0.58 mmol) and an aqueous solu-
the cycloaddition of CO to styrene oxide (SO), the cata-
2
tion of ZnBr (0.80 mmol of H O, 0.16 mmol of ZnBr ),
lyst system consisting of an immobilized tributylmethyl-
ammonium chloride on a polystyrene cross-linked with
divinylbenzene (PS-TBMAC) and an aqueous solution of
2
2
2
an internal standard (0.4 g octane, or nonane, depending on
the olefin used in the process) were added into an autoclave.
1
3

1
570
A. Siewniak et al.
Fig. 1 Model reaction between
O
styrene and carbon dioxide
TBHP
CO2
O
O
O
MoO (acac)2
PS-TBMAC, aq. ZnBr2
2
ST
SO
SC
Table 1 The choice of procedure for conducting the direct synthesis
effect on the epoxidation reaction [14]. In contrast, Arai
et al. found that the addition of carbon dioxide to the first
reaction step results in improved yield both SO and SC
[11]. A low yield of styrene carbonate was obtained pos-
sibly due to the fact that the epoxidation of styrene in the
of styrene carbonate form CO and styrene
2
a
Entry
Procedure
Conversion of the Yield (%)
styrene (%)
SO
BA
SC
1b
1
2
3
3
3
3
79
82
96
94
92
94
8
11
8
21
6
17
19
11
6
23
25
22
43
67
42
51
57
presence of CO could allow the formation of the linear oli-
2
b
2
3
4
5
gomers and polycarbonates, which in turn could impede the
subsequent reaction of carbon dioxide with in situ formed
b
c
epoxide [22, 23]. Therefore, in the next experiment, CO
2
d
was added to the reactor in the second step of the process.
The first step proceeded at the temperature of 100°C. Only
after one hour carbon dioxide was added (0.9 MPa) and the
reaction was carried out for additional 4 h (procedure 2).
This resulted in about a two-fold increase in cyclic carbon-
ate yield (43%) (Table 1, entry 2).
e
6
8
Reaction conditions: styrene (58 mmol), 5.5 M solution of TBHP in
decane (64 mmol), MoO (acac) (0.058 mmol), a quaternary ammo-
2
2
nium salt (0.58 mmol), an aqueous solution of ZnBr (0.80 mmol
2
a
b
of H O, 0.16 mmol of ZnBr ), 500 rpm. Determined by GC. PS-
2
2
c
d
TBMAC. TBMAC TBAB without aqueous solution of ZnBr .
2
The quaternary ammonium salt with a halogen anion
could catalyze the decomposition reaction of tert-butyl
hydroperoxide and MoO (acac) , resulting in the forma-
e
TBAB. Procedure 1: all reagents including the catalyst system con-
sisting of MoO (acac) , PS-TBMAC, aq. ZnBr , were added simul-
2
2
2
taneously to the reactor. Process was conducted at 100°C, under a
2
2
CO pressure of 0.9 MPa for 5 h. Procedure 2: the first stage of pro-
2
tion of oxygen, tert-butanol and MoO Br [15]. Thus, in a
2 2
cess was conducted in the presence of the catalyst system consisting
further experiment CO , PS-TBMAC and an aqueous solu-
2
of MoO (acac) , PS-TBMAC, aq. ZnBr , at 100°C for 1 h, after this
2
2
2
tion of ZnBr were added to the reaction system after one
time carbon dioxide (a CO pressure of 0.9 MPa) was added to the
2
2
reactor and the second step was conducted at 100°C for 4 h. Pro-
cedure 3: the first stage of process was conducted in the presence
of MoO (acac) as catalyst at 100°C for 1 h, after this time carbon
hour (procedure 3). The yield of cyclic carbonate was 67%
(Table 1, entry 3).
2
2
In order to compare, a course of reaction in the presence
dioxide (a CO pressure of 0.9 MPa) and the catalyst system consist-
2
of tributylmethylammonium chloride (TBMAC), which is
a soluble counterpart of PS-TBMAC, the process was car-
ried out according to the procedure 3. As can be seen from
Table 1 (entry 4), the PS-TBMAC showed higher catalytic
activity than its homogeneous counterpart. On the one
hand, this might be due to the increased lipophilicity of
quaternary ammonium salt immobilized onto the polymer
carrier and thus easier contact of the reactants with active
sites of the catalyst. On the other hand, the immobilized
catalyst could show higher stability under reaction condi-
tions. Based on the GC-MS analysis, it was found that dur-
ing the process, 20% of TBMAC underwent decomposition
to tributylamine, which could have a significant impact on
reducing its activity. Moreover, a large amount of unreacted
styrene oxide (an intermediate product) in the post-reaction
mixture also confirmed the lower tributylmethylammonium
chloride activity in the second stage of the process. By con-
trast, in the case of using PS-TBMAC, tributylamine was
observed in an amount less than 1%.
ing of PS-TBMAC (or TBMAC, TBAB) with or without an aqueous
solution of ZnBr were added to the reactor and the second step was
2
conducted for 4 h
zinc bromide(II) (molar ratio of H O to ZnBr 5: 1), was
2
2
applied.
3
.1 The Impact of the Order of Reagent Introduction
The order in which reagents are added to a reactor can be
crucial for the reaction of CO with olefins. The introduc-
2
tion of all reagents: CO , styrene, TBHP with the catalyst
2
system consisting of MoO (acac) , PS-TBMAC and an
2
2
aqueous solution of ZnBr , allowed to obtain styrene car-
2
bonate with only 22% yield (Table 1, entry 1). The unre-
acted styrene oxide (8%) and benzaldehyde (BA) (17%)
were also present in the reaction mixture. In this case, both
stages of the process were carried out under the same con-
ditions of temperature and pressure (procedure 1: 100°C,
the initial CO pressure of 0.9 MPa, 500 rpm, 5 h). Sun
Under the same conditions (procedure 3) the reaction in
presence of TBAB as a catalyst of the second stage of the
2
et al. also observed that the presence of CO has a negative
2
1
3

Efficient Catalytic System Involving Molybdenyl Acetylacetonate and Immobilized…
1571
SC
Table 2 The influence of
a
Entry
Temperature of the CO pressure Amount of the PS-
Conversion of Yield (%)
2
temperature and CO pressure
2
2
stage (°C)
(MPa)
TBMAC (% mol)
ST (%)
on the second stage of the direct
SO
BA
synthesis of styrene carbonate
from CO and styrene
1
2
3
4
5
6
7
8
9
90
0.9
0.9
0.9
0.9
0.9
0.5
1.5
2.0
0.9
0.9
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.5
3.0
96
96
97
96
98
96
97
97
97
97
32
8
5
9
2
21
4
4
8
13
6
11
7
5
8
6
4
4
10
8
31
67
45
30
19
29
51
34
68
70
2
100
110
120
130
100
100
100
100
100
1
0
Reaction conditions: styrene (58 mmol), 5.5 M solution of TBHP in decane (64 mmol), MoO (acac)
2
2
(
0.058 mmol), PS-TBMAC, aqueous solution of ZnBr (0.80 mmol of H O, 0.16 mmol of ZnBr ),
2
2
2
5
00 rpm. The first step of process was conducted in the presence of MoO (acac) at 100°C, 1 h; after this
2
2
time carbon dioxide (a CO pressure of 0.9 MPa) and the catalyst system consisting of PS-TBMAC and aq.
2
a
ZnBr were added to the reactor and the second step was conducted for 4 h. Determined by GC
2
process (Table 1, entry 5), and the reaction with the catalyst
Moreover, at high pressure of CO , the formation of oli-
2
system consisting of TBAB and aq. ZnBr , were carried out
gomers can be promoted [14].
2
(
Table 1, entry 6). In both cases, the yield of SC was lower
The increase of the amount of immobilized catalyst in
the studied range (1–3 mol% to styrene) has a negligible
impact on the yield of styrene carbonate. It should also be
emphasized that the excessive amount of the immobilized
catalyst in the reaction system may impede mixing of the
reaction mixture.
than that obtained in the case of using PS-TBMAC and aq.
ZnBr .
2
3
.2 The Choice of Conditions of the Second Step
of the Process
Conditions for carrying out the first reaction step using
MoO (acac) as a catalyst, have been chosen on the basis
2
2
of literature data (100°C, 1 h) [15]. Whereas, the influ-
8
0
ence of temperature and CO pressure on the course of the
2
70
second stage of the reaction was examined. Optimal condi-
tions for conducting the second stage of the direct synthesis
of cyclic carbonates may be different from those we have
60
50
40
specified for their synthesis from epoxides and CO in the
2
Yield
presence of PS-TBMAC [21], since in this case the reaction
mixture is more complex. As shown in Table 2, the tem-
perature increase from 90 to 100°C in the second stage of
the process caused more than two-fold increase in a yield
of styrene carbonate. When the temperature raised, the rate
of the reaction of carbon dioxide with in situ formed sty-
rene oxide also increased. However, a further increase of
temperature above 100°C had an unfavorable effect on the
reaction course.
3
0
Selecꢀvity
20
10
0
1
2
3
4
5
Run
Fig. 2 PC yield and selectivity in the reaction of CO with sty-
2
rene in the presence of recycled PS-TBMAC catalyst. Reaction
The styrene carbonate yield increased with pres-
sure increasing from 0.5 to 0.9 MPa. However, a further
conditions: styrene (58 mmol), 5.5 M solution of TBHP in decane
(
64 mmol), MoO (acac) (0.058 mmol), PS-TBMAC (0.58 mmol),
2 2
increase in the CO pressure resulting in lowered SC
aqueous solution of ZnBr (0.80 mmol of H O, 0.16 mmol of ZnBr ),
2 2 2
2
5
00 rpm. The first step of process was conducted in the presence
yield. This phenomenon has also been observed by other
researchers. Some of them explain that too high con-
centration of carbon dioxide in the reaction mixture can
hinder the interaction between styrene and catalyst [13].
of MoO (acac) at 100°C, 1 h, after this time carbon dioxide (a
2
2
CO pressure of 0.9 MPa) and the catalyst system consisting of PS-
2
TBMAC and aq. ZnBr were added to the reactor and the second step
2
was conducted for 4 h
1
3

1
572
A. Siewniak et al.
Table 3 Synthesis of various
O
PS-TBMAC
aqueous solution of ZnBr2
cyclic carbonates from olefins
MoO (acac) ,TBHP
and CO2
2
2
O
O
R
O
R
1
00 °C or 70 °C, 1 h
0.9 MPa of CO, 100 °C, 4 h
2
R
1a-d
2a-d
3a-d
O
O
O
O
O
O
O
O
O
Cl
c
3
a
3b
Y:55
3c
a
b
Y: 67
b
Y: 75
a
C: 96
O
O
O
O
O
O
O
O
O
H C
H C
13 6
9
4
d
3
d
3e
Y: 77
3f
b
a
Y: 50
b
Y: 4
a
C: 97
a
C: 87
Reaction conditions: olefin (58 mmol), 5.5 M solution of TBHP in decane (64 mmol), MoO (acac)
2
2
(
0.058 mmol), PS-TBMAC (0.58 mmol), aqueous solution of ZnBr (0.80 mmol of H O, 0.16 mmol of
2
2
ZnBr ), 500 rpm. The first step of the process was conducted in the presence of MoO (acac) at 100°C,
2
2
2
1
h; after this time carbon dioxide (CO pressure of 0.9 MPa) and the catalyst system consisting of PS-
2
TBMAC and aq. ZnBr were added to the reactor and the second step was conducted for 4 h. Y—yield of
2
a
b
1
c
cyclic carbonate (%), C—olefin conversion (%). Determined by GC. Determined by H NMR. Tempera-
d
ture of the first stage: 70°C. Cis-isomer, time of the second stage: 10 h
3
.3 Studies on the Recycle of PS‑TBMAC
in the process. The recovery of MoO (acac) was only
2 2
4
8%. Therefore, in subsequent reactions, the addition of
Reusability of the catalyst is important from the economic
point of view. Therefore, study on the recovery and reuse
of the catalyst system was conducted. The process was per-
formed under the optimized conditions described above
fresh MoO (acac) was used. It should be noted that if the
2 2
reaction is conducted on a large scale, these losses may be
negligible.
The results shown in Fig. 2, indicate that the PS-
TBMAC catalyst exhibited high activity in five successive
cycles of reaction. Cyclic carbonate yields in subsequent
cycles ranged 65–67%.
(
the first step at 100°C for 1 h, the second step at 100°C
and under a pressure of 0.9 MPa CO for 4 h).
2
The immobilized PS-TBMAC catalyst was separated
from the reaction mixture by filtration, whereas molybde-
nyl acetylacetonate by extraction with ethanol and subse-
quent filtration of the precipitated catalyst. These catalysts
with a fresh solution of zinc bromide were used for the next
process for the preparation of styrene carbonate. However,
the yield of styrene carbonate was lower than for the fresh
catalyst system. This may be due to losses in the recovery
of MoO (acac) , because it was used in very small amount
3.4 Synthesis of Cyclic Carbonates from Selected
Olefins and CO
2
The cyclic carbonates from selected olefins and CO in the
2
presence of the developed catalytic system: MoO (acac) /
2
2
PS-TBMAC/aqueous solution of ZnBr , were synthesized.
2
The first step of the process was carried out at 100°C (or
2
2
1
3

Efficient Catalytic System Involving Molybdenyl Acetylacetonate and Immobilized…
1573
at 70°C for allyl chloride as a substrate) for 1 h, and the
second stage at a temperature of 100°C and a pressure of
link to the Creative Commons license, and indicate if changes were
made.
0
.9 MPa CO for 4 h.
2
Cyclic carbonates were obtained in yields within a range
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use, distribution, and reproduction in any medium, provided you give
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(
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