Catalyst Systems Based on a Metal Halide and a Quaternary Ammonium Salt in the 1,2-Epoxycyclopentane Carboxylation Reaction

Article abstract of DOI:10.1134/S096554411810016X

Abstract: Results of a study of 1,2-epoxycyclopentane carboxylation to cyclopentene carbonate (CPC) in the presence of various catalyst systems have been described. It has been found that the reaction occurs most efficiently in the presence of cobalt (nickel) chloride (bromide) hydrate and a quaternary ammonium salt (TEAB, TBAB). It has been recommended that CPC should be synthesized under a CO₂ pressure of no less than 3.5 MPa at a temperature of 140–150°С without any solvent or in the medium of a solvent, such as target CPC, DMF, or N-MP, at a 1,2-epoxycyclopentane weight fraction in the feed mixture of no less than 25%. These conditions provide the formation of CPC with a selectivity of 97–99% and almost complete epoxide conversion within 2–4 h. It has been shown that the developed catalyst system can be recycled.

Full text of DOI:10.1134/S096554411810016X

ISSN 0965-5441, Petroleum Chemistry, 2019, Vol. 59, No. 1, pp. 78–84. © Pleiades Publishing, Ltd., 2019.
Russian Text © G.Yu. Taranenko, G.V. Rybina, S.S. Srednev, A.E. Meshechkina, A.V. Tarasov, 2019, published in Neftekhimiya, 2019, Vol. 59, No. 1, pp. 76–82.
Catalyst Systems Based on a Metal Halide
and a Quaternary Ammonium Salt in the 1,2-Epoxycyclopentane
Carboxylation Reaction
G. Yu. Taranenkoa, G. V. Rybinaa, *, S. S. Sredneva, A. E. Meshechkinaa, and A. V. Tarasova
aYaroslavl State Technical University, Yaroslavl, Russia
*e-mail: rybinagv@ystu.ru
Received January 18, 2018; Revised March 18, 2018; Accepted July 26, 2018
Abstract—Results of a study of 1,2-epoxycyclopentane carboxylation to cyclopentene carbonate (CPC) in the
presence of various catalyst systems have been described. It has been found that the reaction occurs most effi-
ciently in the presence of cobalt (nickel) chloride (bromide) hydrate and a quaternary ammonium salt
(TEAB, TBAB). It has been recommended that CPC should be synthesized under a CO2 pressure of no less
than 3.5 MPa at a temperature of 140–150°С without any solvent or in the medium of a solvent, such as target
CPC, DMF, or N-MP, at a 1,2-epoxycyclopentane weight fraction in the feed mixture of no less than 25%.
These conditions provide the formation of CPC with a selectivity of 97–99% and almost complete epoxide
conversion within 2–4 h. It has been shown that the developed catalyst system can be recycled.
Keywords: carboxylation, 1,2-epoxycyclopentane, catalytic systems
DOI: 10.1134/S096554411810016X
Cyclic organic carbonates (COCs) are promising
products of industrial organic synthesis. Despite the
wide ranges of practical application of these materials,
low-molecular-weight COCs, such as ethylene car-
bonate and propylene carbonate, are being most com-
monly produced [1].
O
O
C O
CPC
O + CO2
ECP
O
O
C
In recent decades, the attention of researchers has
been increasingly given to the synthesis of alicyclic
COCs, in particular, cyclopentene carbonate (CPC).
The growing interest in CPC is attributed to the possi-
bility of using this material both as a high-efficiency
chlorine-free solvent [2] and as a monomer in the syn-
thesis of a number of highly durable biodegradable
urethane-containing polymers synthesized by an envi-
ronmentally friendly isocyanate-free technology [3].
O
n
poly(cyclopentene carbonate)
The route—the formation of CPC or poly(cyclo-
pentene carbonate)—is largely determined by the
nature of the catalyst.
A number of authors described the reaction
between ECP with CO2 in the presence of tetraeth-
ylammonium bromide (TEAB), tetramethylammo-
nium bromide (TMAB), and tetrabutylammonium
bromide (TBAB) quaternary ammonium salts (QASs)
[7, 8] and a binary catalyst system composed of TEAB
and an alkali metal bromide (iodide) [9]. Despite the
high CPC yield, which achieves 92%, the catalyst
looses activity because it undergoes partial decompo-
sition under the reaction conditions.
The currently available methods for synthesizing
CPC from cyclopentene [4] and 1,2-cyclopentanediol
[5, 6] have significant disadvantages, namely, the tox-
icity of the reactants used, a low CPC yield, and the
formation of a significant amount of byproducts.
Therefore, the production of CPC by the carboxyl-
ation of 1,2-epoxycyclopentane (ECP) can be thought
of as the most promising, competitive, and environ-
mentally friendly method (so-called “green chemis-
try” technology) for CPC synthesis.
A number of zinc-based organometallic catalysts
for ECP carboxylation were proposed [4, 6, 10]; the
The ECP carboxylation reaction can occur mostly use of these catalysts leads to the formation of
via two routes:
poly(cyclopentene carbonate) with a yield of 65–99%.
78

CATALYST SYSTEMS BASED ON A METAL HALIDE
79
At 25–70°C and a CO2 pressure of 0.1–5.0 MPa, the
EDS conversion does not achieve a value of more than
48% within 12–24 h. The cyclopentene oxide conver-
sion of up to 56% was obtained under the same condi-
tions within 3–6 h in the presence of binary salen cat-
alysts (salen)CоCl/PPNN3 and (salen)CrCl/TBAH;
however, in this case, the CPC yield was 68–83% [10].
The use of porphyrin complexes of Mg, Co, Ni,
Cu, Zn, and Al with a cocatalyst (QAS) [11] or a
bifunctional 5,10,15,20-(porphyrin)AlCl/N-methyl-
imidazole catalyst [12, 13] provides the formation of
CPC with a yield of 54–90%. The reaction occurs at a
temperature of 90–120°C and a pressure of 1–
4.8 MPa in a medium of an aprotic solvent (HMPA,
DMF) or the target CPC.
Thus, the reaction between ECP and carbon diox-
ide in the presence of most of the known catalysts
occurs with a low CPC yield or a low ECP conversion;
it is characterized by a long synthesis time, the need
for using a solvent, the complexity of catalyst synthe-
sis, and/or the impossibility of regenerating the cata-
lyst.
The solvents DMF, DMAA, N-MP, acetonitrile,
and formamide were of the “chemically pure” grade
and were subjected to fractional distillation before
synthesis; the assay was no less than 99.0% according
to GLC data.
1,2-Epoxycyclopentane was produced by cyclo-
pentene oxidation with an aqueous solution of hydro-
gen peroxide according to a known procedure [14] and
isolated by distillation with a weight fraction of 99.5%;
the residual water content was no more than 0.3%;
T = 102°C; and 20 = 1.4336.
nd
b
Gaseous carbon dioxide corresponded to GOST
8050-85.
Tetramethylammonium bromide (chemically
pure) corresponded to TU 71-91-0; assay, 99.0%.
Other materials used were as follows: CoCl2 · 6H2O
(GOST 4525-77), AlCl3 ⋅ 6H2O (GOST 3759-75),
СrCl3 ⋅ 6H2O (GOST 4473-78), SnCl2 ⋅ 2H2O (GOST
36-78) and NiCl2 ⋅ 6H2O (GOST 4038-79), all of the
chemically pure grade, and reagent grade KI (GOST
4232-74).
Cyclopentene carbonate was isolated by rectification
with a weight fraction of 99.7%, Tb = 170°C/2 mmHg,
and Tm = 32.5–35°C.
The aim of this study is to develop effective catalyst
systems for cyclopentene carbonate synthesis from
1,2-epoxycyclopentane and CO2 and test the resulting
catalysts.
1
The CPC structure was confirmed by H NMR,
13C NMR, and mass spectroscopy. The 1H NMR and
13C NMR spectra were recorded on a Bruker DRX400
spectrometer using DMSO-d6 as the solvent and
tetramethylsilane as the internal standard.
EXPERIMENTAL
The ECP carboxylation reaction was run in a
60-cm3 titanium reactor equipped with a jacket for cir-
culating a heat transfer fluid (glycerol). A pressure
gage, a sampling valve, and a CO2 supply valve were
embedded in the reactor cover; a well for a thermo-
couple was mounted into the reactor floor. Feed ECP,
a solvent (20 cm3), and the catalyst components were
loaded into the carbon dioxide-purged reactor at room
temperature. A constant CO2 pressure was maintained
by means of a reducing valve mounted on the line of
gas supply from a cylinder. A required temperature was
maintained by means of a thermostat with an accuracy
of 1.0°C. Upon the achievement of an operating
temperature in the reactor, a mechanical shaker was
turned-on to provide a stirring speed of no less than
140 rpm. At regular intervals during the test, samples
for analysis were taken from the reactor and placed
Infrared spectra were recorded on a PerkinElmer
Spectrum RX-1 FTIR spectrometer at wavelengths of
700–4000 cm–1. The analyte had the form of a suspen-
sion in vaseline oil; KBr plates were used. Mass spectra
were recorded on a Shimadzu Prominence LCMS-
2020 high-performance liquid chromatograph–mass
spectrometer equipped with a chromatographic col-
umn (T = 40°C; eluent, acetonitrile) and a mass spec-
trometer (LCMS-2020; m/z range, 0–2000; ioniza-
tion modes, ESI/ACPI).
IR, ν/cm–1: 1780 (C=O), 1172, 1112, 10 47 (C–
1
O‒C). H NMR (400 MHz, δ, ppm): 1.45–1.62 (m,
1H, H5), 1.62–1.77 (m, 3H, H5, H4, H6), 1.88–
2.00 (m, 2H, H4, H6), 5.12–5.20 (m, 2H, H3a, H6a).
13C NMR (75 MHz, δ, ppm): 21.38 (1C, C5), 32.44
into sealed tubes. The reaction time was counted from (2C, C4, C6), 81.89 (2C, C3a, C6a), 155.07 (1C, C=O).
ESI, m/z (Irel (%)): 127 [M]+. It was found that, in the
presence of the CoCl2 ⋅ 6H2O–TEAB catalyst system,
the cis-isomer of CPC is formed.
the time at which the shaker was turned-on.
Reaction products were analyzed on a Chromatec
Kristall 5000.2 gas chromatograph equipped with a
flame ionization detector and a CR-WAXms capillary
column (30 m × 0.32 mm), using column temperature
programming from 60 to 160°C at a heating rate of
10°C/min and the carrier gas (hydrogen) at a flow rate
of 40 cm3/min. The injected sample volume was
0.2 μL. Undecanol-1 was used as the internal stan-
dard.
RESULTS AND DISCUSSION
A catalyst system composed of a cobalt (nickel)
halide and DMF was proposed previously; it showed
high efficiency for the synthesis of cyclic carbonates
from monoalkyl-substituted С5–С16 ethylene oxides,
PETROLEUM CHEMISTRY Vol. 59 No. 1 2019

80
TARANENKO et al.
Table 1. Effect of the solvent and the catalyst nature on the
cyclopentene carbonate synthesis parameters. Conditions:
temperature, 150°C; carbon dioxide pressure, 2 MPa;
weight fraction of epoxycyclopentane in the feed mixture,
2.9 mol/dm3; catalyst concentration, 0.0345 mol/mol ECP;
and reaction time, 180 min
C4 and C8 diene monoepoxides, epichlorohydrin, and
styrene oxide [15]. Therefore, it was of interest to use
this system in the ECP carboxylation reaction. To
compare the activity, tests were conducted in the pres-
ence of TEAB and KI catalysts (Table 1), which are
most commonly used in commercial syntheses of
lower COCs [4]. The ECP carboxylation reaction was
run in a DMF medium and in the solvent-free mode.
In the absence of a solvent, the formation of CPC
occurs with a high selectivity of 89.5% only in the
presence of the TEAB catalyst (Table 1, entry 5).
Under the same conditions, KI and СоCl2 ⋅ 6H2O
hardly catalyze the ECP conversion to CPC: the pro-
cess selectivity is extremely low—2 or 3% at an
epoxide conversion of 3 or 12%, respectively (Table 1,
entries 3, 7). This finding is apparently attributed to
the low solubility of metal halides in cyclopentene
oxide.
It was found that DMF is capable of catalyzing the
reaction between CO2 and ECP. Within 3 h, the epox-
ide conversion achieves 5.5% at a CPC selectivity of
35% (Table 1, entry 1). The catalytic activity of DMF
in the carboxylation of aliphatic epoxides was previ-
ously observed by Rui et al. [16].
It was shown that the efficiency of the catalysts
increases if the reaction is run in a DMF medium.
Thus, in the presence of TEAB, at a temperature of
150°C and a CO2 pressure of 2 MPa, the ECP conver-
sion achieved 90.1% for 3 h with a CPC selectivity of
91.3% (Table 1, entry 4). In the case of catalysis by
cobalt chloride, the ECP conversion reached 87%;
however, the selectivity remained low at a level of no
more than 48% (Table 1, entry 2). The use of KI as a
CPC synthesis catalyst is extremely inefficient even in
a DMF medium (Table 1, entry 6).
Thus, the use of СоCl2 ⋅ 6H2O in a DMF medium
for CPC synthesis from ECP and CO2 did not provide
the same high values as those obtained in the carbox-
ylation of acyclic С5–С16 epoxides [15]. This finding is
apparently due to the fact that the reactivity of cyclo-
olefin oxides in this reaction is lower than the reactiv-
ity of aliphatic epoxides, a difference that was noted in
a number of papers [10, 17].
It is known that in the literature, binary catalyst
systems are considered to be the most effective cata-
lysts for the carboxylation of epoxides of various struc-
tures [4]. They include Lewis acid (metal halide) and
a nucleophilic component (typically, a quaternary
ammonium salt). Therefore, binary catalyst systems
based on chromium, aluminum, cobalt, and nickel
halides in combination with quaternary ammonium
salts were tested in this study (Table 2). Organometal-
lic catalysts based on these metals were proposed by a
number of authors for the carboxylation of alicyclic
С6–С12 epoxides [16–18].
ECP
CPC
No.
Catalyst
None
Solvent conversion, selectivity,
%
%
1
2
3
4
5
6
7
DMF
DMF
None
DMF
None
DMF
None
5.55
86.03
12.53
90.12
66.46
22.55
3.14
35.11
48.07
2.33
CoCl2 · 6H2О
TEAB
91.34
89.53
8.71
KI
3.35
ited by the catalyst systems based on a cobalt (or
nickel) halide and TEAB (or TBAB) both in a solvent
medium (DMF, N-MP) and in the absence of a sol-
vent (Table 2, entries 4–7, 12, 13). At a temperature of
150°C and a pressure of 2 MPa, this binary catalyst
system provided an ECP conversion of more than 99%
with a CPC selectivity of up to 97%. Data on the influ-
ence of the nature of the solvent on the carboxylation
reaction parameters (Table 1; Table 2, entries 6–11)
show that it has a significant effect on the cycloaddi-
tion reaction rate, as was repeatedly reported by other
authors [10]. Apparently, the role of the solvent goes
beyond changing the physicochemical properties of
the reaction medium: it is part of the catalyst system.
According to expectations, in the case of using
hydrates of metal salts in carboxylation, a secondary
reaction is the ECP hydrolysis to form CPDiol
(Table 2), which hinders the isolation of CPC from
the reaction mixture. In addition, the CPC synthesis
products included cyclopentanone, which is formed
during the ECP isomerization in the presence of Lewis
acids [19], and halohydrins, the formation of which
was also observed in the divinyl oxide carboxylation
[15]. Poly(cyclopentene carbonate) was not detected
in the reaction mixture.
Studies of the effect of the initial ECP concentra-
tion on the parameters of CPC synthesis in the pres-
ence of the catalyst system composed of CoCl2 ⋅ 6H2O
and TEAB in a DMF medium (Fig. 1) revealed that,
with an increase in the ECP content in the feed mix-
ture to 2 mol/dm3, the epoxide conversion and the
CPC selectivity rapidly increase; within 240 min,
these parameters achieve 93.2 and 97.1%, respectively.
A further increase in the initial ECP concentration
leads only to a slow increase in the ECP conversion; at
a C0(ECP) value of 8.93 mol/dm3 (solvent-free syn-
Analysis of the results (Table 2) showed that the
highest activity in the targeted CPC synthesis is exhib- thesis), the epoxide conversion was 98.3% with a CPC
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CATALYST SYSTEMS BASED ON A METAL HALIDE
81
Table 2. Effect of the nature of the metal halide and the solvent on the parameters of CPC synthesis in the presence of a
binary catalyst system with TEAB. Conditions: temperature, 150°C; CO2 pressure, 2.0 MPa; initial ECP concentration,
2.9 mol/dm3; MeH catalyst concentration, 0.0041 mol/mol ECP; MeH : TEAB catalyst molar ratio, 1 : 4; and reaction
time, 240 min
Selectivity, %
CPDiol*
ECP
conversion, %
No.
Metal halide
Solvent
CPC
other
AlCl3 ⋅ 6H2O
СrCl3 ⋅ 6H2O
SnCl2 ⋅ 2H2O
NiCl2 ⋅ 6H2O
NiBr2 ⋅ 3H2O
1
2
DMF
73.78
96.36
96.41
97.16
98.80
99.71
99.41
87.54
69.00
31.49
99.63
98.30
22.55
87.18
83.29
96.88
96.28
97.15
96.01
96.26
94.47
96.80
97.84
98.11
96.84
14.10
12.80
16.45
2.77
2.43
2.81
2.17
63.35
0.02
0.26
0.35
1.29
0.04
1.82
1.57
4.26
0.73
0.05
1.08
0.13
DMF
3
DMF
4
DMF
5
DMF
6
DMF
7
N-MP
8
DMAA
Formamide
Acetonitrile
CPC
0.72
1.27
2.47
2.11
9
СоCl2 ⋅ 6H2O
10
11
12
13
None**
DMF***
0.81
3.03
99.12
3
* 1,2-Cyclopentadiol. ** The initial ECP concentration is 8.93 mol/dm . ** TBAB QAS.
selectivity of 98.1%. Apparently, the resulting CPC ylation reaction were conducted in the absence of a
contributes to the activation of the reaction between solvent.
ECP and CO2. This assumption is supported by high
The effect of the concentration of the catalyst sys-
parameters of cyclocarbonate synthesis in the target
tem components on the CPC synthesis parameters at
CPC medium and in the absence of a solvent (Table 2,
a constant feed molar ratio of CoCl2 ⋅ 6H2O : TEAB =
entries 11, 12). The further studies of the ECP carbox-
1
3
100
90
80
70
60
50
40
30
20
10
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2
ECP conversion, CPC selectivity, %
100
1
90
80
70
60
50
40
30
20
10
2
4
0
0.005
0.010
0.015
0.020
CoCl2 · 6H2O concentration, mol/mol ECP
0
1
2
3
4
5
6
7
8
9
10
Fig. 2. Effect of the concentration of the catalytic system
components on the ECP conversion and the CPC and
CPDiol selectivity: ECP conversion (%) within (1) 240
and (3) 120 min, (2) CPC selectivity (%) within (line) 240
and (symbols) 120 min, and (4) CPDiol selectivity (%)
Initial ECP concentration, mol/L
Fig. 1. Effect of the initial ECP concentration on (1) CPC
selectivity (%) and (2) ECP conversion (%). Conditions:
temperature, 150°C; CO pressure, 2.0 MPa; molar ratio,
within 240 min. Conditions: temperature, 150°C; CO
2
2
CoCl ⋅ 6H O : TEAB = 1 : 1; CoCl ⋅ 6H O concentra-
pressure, 2.0 MPa; initial ECP concentration,
2
2
2
2
3
tion, 0.0345 mol/mol ECP; solvent, DMF; and reaction
time, 240 min.
8.93 mol/dm ; molar ratio, CoCl ⋅ 6H O : TEAB = 1 : 1;
2 2
solvent-free synthesis.
PETROLEUM CHEMISTRY Vol. 59 No. 1 2019

82
TARANENKO et al.
Table 3. Effect of the molar ratio of the CoCl2 ⋅ 6H2O–TEAB catalyst system components on the CPC synthesis parame-
ters. Conditions: temperature, 150°C; CO2 pressure, 2.0 MPa; initial ECP concentration, 8.93 mol/dm3; solvent-free syn-
thesis
Selectivity, %
CPDiol
CoCl2 ⋅ 6H2O : TEAB
ECP
conversion, %
No.
Time, min
molar ratio
CPC
other*
TEAB concentration of 0.0044 mol/mol ECP
120
180
240
120
180
240
120
180
240
120
180
240
120
180
240
61.1
74.8
83.1
74.3
90.9
97.0
84.1
96.0
98.3
83.0
97.3
98.1
80.5
93.1
98.0
98.6
98.0
97.9
98.1
97.8
97.8
98.0
97.5
97.5
98.3
98.5
98.6
97.3
96.2
96.5
1.1
1.2
1.1
0.4
0.4
0.4
0.7
0.7
0.7
0.8
0.7
0.7
1.0
1.0
1.0
0.3
0.8
1.0
1.5
1.8
1.8
1.3
1.8
1.8
0.9
0.8
0.7
1.7
2.8
2.5
1
2
3
4
5
0.125 : 1
0.25 : 1
0.5 : 1
1 : 1
2 : 1
CoCl2 ⋅ 6H2O concentration of 0.0044 mol/mol ECP
120
180
240
120
180
240
97.9
99.3
99.6
38.6
52.0
65.3
98.7
98.8
99.1
96.2
96.3
96.2
0.7
0.7
0.7
1.5
1.5
1.4
0.6
0.5
0.2
2.3
2.2
2.4
6
7
1 : 2
1 : 0.5
* Cyclopentanone and 2-chlorocyclopentanol-1.
1 : 1 was studied (Fig. 2). It was found that, with an
increase in the CoCl2 ⋅ 6H2O–TEAB catalyst system
concentration from 0.0044 to 0.0087 mol/mol ECP, at
a molar ratio of the components of 1/1, the ECP con-
version and the CPC selectivity increase and achieve a
maximum value of 98.5–99.2% within 240 min. With
a further increase in the catalyst content in the reac-
tion mixture to 0.0348 mol/mol ECP, these parame-
ters of the process remain almost unchanged
(curves 1, 2); however, the CPDiol yield decreases
(curve 4) and the proportion of the epoxide isomeriza-
tion products increases. It should be noted that the
Assuming that the initial system components pri-
marily form a catalytic complex (complexes) that acti-
vates the carboxylation reaction, we studied the effect
of the molar ratio between CoCl2 ⋅ 6H2O and TEAB
(Table 3). In this case, both the excess and deficiency
of the catalyst system components with respect to each
other were varied.
In the case of variation in the cobalt chloride con-
tent in the reaction mixture from 0.0006 to
0.0088 mol/mol ECP (Table 3, entries 1–5) at a con-
stant TEAB concentration of 0.0044 mol/mol ECP, it
is evident that the ECP conversion does not exceed
reaction time (240 or 120 min) affects only the epoxide 84% in the entire CoCl2 ⋅ 6H2O concentration range
conversion (curves 1, 3); the CPC selectivity does not
change over the entire duration of the reaction
(curve 2, line and symbols).
with a CPC selectivity of about 98% at a reaction time
of 120 min. The ECP conversion of at least 97% can be
achieved within 4 h at a CoCl2 ⋅ 6H2O : TEAB molar
PETROLEUM CHEMISTRY
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CATALYST SYSTEMS BASED ON A METAL HALIDE
83
Table 4. Effect of CO2 pressure and temperature on the ECP carboxylation reaction. Conditions: initial ECP concentra-
tion, 8.93 mol/dm3; CoCl2 concentration, 0.0010 mol/mol ECP; and CoCl2 ⋅ 6H2O : TEAB molar ratio, 1 : 4
Selectivity, %
CPDiol
СО2 pressure,
MPa
Temperature,
ECP
conversion, %
No.
Time, min
°С
CPC
other
120
180
240
120
180
240
120
180
240
120
180
240
240
240
120
180
240
65.9
81.5
91.1
74.3
90.9
97.0
91.2
98.8
99.9
88.2
98.1
99.5
2.4
97.4
97.1
97.1
98.1
97.8
97.8
98.5
98.7
98.0
98.4
98.6
98.4
90.9
96.4
95.7
95.5
95.7
0.5
0.5
0.5
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
0.4
2.5
2.3
2.0
1.9
1.8
2.1
2.4
2.4
1.5
1.8
1.8
1.1
1
150
150
150
150
1.0
2.0
3.5
4.5
2
3
4
0.9
1.6
1.2
1.0
1.2
6.6
1.3
2.3*
2.6*
2.5*
5
6
110
130
2.0
2.0
15.7
52.5
77.6
89.4
7
160
2.0
* Mostly high-boiling compounds.
ratio of 0.25–0.5 : 1 (Table 3, entries 2, 3) or within 3 h 3 h of reaction at a CPC selectivity of about 99%
at a ratio of 1 : 1 (Table 3, entry 4). In this case, the for- (Table 3, entry 6). It should be noted that the molar
mation of CPC occurs with a selectivity of 97.5–98%. excess of CoCl2 ⋅ 6H2O with respect to TEAB leads to
However, even at a cobalt chloride concentration of
0.0088 mol/mol ECP (Table 3, entry 5), the CPC
selectivity decreases to 96% with increasing reaction
time. With an increase in the CoCl2 ⋅ 6H2O concentra-
tion, the CPDiol yield on a converted ECP basis
slightly increases and achieves 0.8 0.2%. This fact is
apparently attributed to the introduction of a larger
amount of crystallization water with the catalyst. At
the same time, the yield of other byproducts, mostly
cyclopentanone, exhibits a minimum at an equimolar
ratio of cobalt chloride and TEAB (Table 3, entry 4).
It should be noted that the selectivity for CPDiol and
other byproducts varies only slightly with an increase
in the reaction time from 1 to 3 h.
an increase in the proportion of ECP isomerization
products in the reaction mixture (Table 3, entries 5, 7).
In addition, the data of Tables 2 and 3 suggest that
in order to achieve high parameters in the CPC syn-
thesis, it is important to maintain not only a certain
molar ratio of the components of the binary system,
but also their total content relative to the initial ECP
concentration.
The effect of the carbon dioxide pressure and the
reaction temperature was examined; it was found that
they significantly affect only the ECP conversion
(Table 4).
It was found that an almost complete consumption
of the epoxide can be achieved at a CO2 pressure of
3.5 MPa and above within 4 h. In this case, the CPC
selectivity is no less than 98% (Table 4, entries 3, 4).
With an increase in pressure, the CPDiol yield
remains almost unchanged at a level of 0.4–0.5%,
while the formation of other byproducts decreases to
A moderate TEAB content in the reaction mixture
(0.0022 mol/mol ECP)—two times lower than the
cobalt chloride hexahydrate content (Table 3,
entry 7)—leads to a significant decrease in the carbox-
ylation rate, although the CPC selectivity remains
fairly high (96%). An increase in the TEAB content to
0.0044 mol/mol ECP and higher values provides an 110 and 130°C (Table 4, entries 5, 6), the reaction rate
increase in the reaction rate. Owing to this effect, the is extremely low; at 130°C, the ECP conversion does
ECP conversion achieved a value above 99% within not exceed 20% within 240 min. The decrease in the
1
0.2% at a pressure of 4.5 MPa. At temperatures of
PETROLEUM CHEMISTRY Vol. 59 No. 1 2019

84
TARANENKO et al.
process rate at 160°C (entry 7) is apparently due to the
partial thermal degradation of TEAB [20]. The
CPDiol content in the reaction mixture increases; the
formation of other high-boiling compounds is
observed (Table 4, entry 7).
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Translated by M. Timoshinina
PETROLEUM CHEMISTRY
Vol. 59
No. 1
2019