Reaction of carbon tetrachloride with hydrogen peroxide

Article abstract of DOI:10.1007/s11178-005-0031-3

Reaction of carbon tetrachloride with aqueous hydrogen peroxide in the presence of anhydrous iron(III) chloride was studied. Optimal conditions for the preparation of phosgene were found on the basis of analysis of the kinetic data and mechanism of the process. The reaction rate and yield (the latter reaching 95% in the stationary mode) are determined mainly by the amount of the heterogeneous catalyst. According to the experimental data, the reaction follows a radical mechanism.

Full text of DOI:10.1007/s11178-005-0031-3

Russian Journal of Organic Chemistry, Vol. 40, No. 10, 2004, pp. 1403–1406. Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004,
pp. 1455–1458.
Original Russian Text Copyright © 2004 by Tatarova, Trofimova, Gorban’, Khaliullin.
Reaction of Carbon Tetrachloride with Hydrogen Peroxide
L. A. Tatarova, K. S. Trofimova, A. V. Gorban’, and A. K. Khaliullin
Favorskii Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
e-mail: sypol@irioch.irk.ru
Received April 15, 2003
Abstract—Reaction of carbon tetrachloride with aqueous hydrogen peroxide in the presence of anhydrous
iron(III) chloride was studied. Optimal conditions for the preparation of phosgene were found on the basis of
analysis of the kinetic data and mechanism of the process. The reaction rate and yield (the latter reaching 95%
in the stationary mode) are determined mainly by the amount of the heterogeneous catalyst. According to the
experimental data, the reaction follows a radical mechanism.
Carbon tetrachloride is a large-scale product which
is obtained mainly by treatment of waste products in
the manufacture of organochlorine compounds. A large
part of carbon tetrachloride was utilized in the
manufacture of Freons 11 and 12 [1]. In keeping with
the Montreal Convention, just these compounds are
most hazardous for the ozone layer [2], so that their
large-scale production was terminated. Another pos-
sible way for utilization of carbon tetrachloride is its
conversion into phosgene. The latter is an important
reagent for organic synthesis and is widely used in the
preparation of medicines (as chloroformylating agent)
We have developed a procedure for the preparation
of phosgene by oxidation of carbon tetrachloride with
aqueous hydrogen peroxide in the presence of an-
hydrous iron(III) chloride. The reaction occurs at the
boiling point of the mixture (72–73°C). Decomposition
of carbon tetrachloride by the action of aqueous
hydrogen peroxide may be described by the following
general scheme:
FeCl3
2CCl
+
2H
+
O
2COCl
+
4HCl
2HCl
+
O
2
4
2
2
2
FeCl3
CCl4
H O
2
COCl2
+
[
3], isocyanates, and polycarbonates [4–6].
In order to find optimal conditions of the process,
we examined the relations between the yield of
phosgene and the concentrations of hydrogen peroxide
In the worldwide industrial practice, carbon tetra-
chloride is processed at the same place where it is
produced. However, the traditional procedure for the
synthesis of phosgene from CO and Cl [7] is hardly
Yield, mol/mol
2
acceptable for factories utilizing relatively small
amounts of carbon tetrachloride since the efficiency of
such a plant is at least 10000 tons per annum.
0
0
0
0
.8
.7
.6
.5
According to published data [8, 9], hydrolysis of
carbon tetrachloride in the presence of Friedel–Crafts
catalysts, such as SbCl , GaCl , FeCl , and FeCl ·
5
3
3
3
0.4
4
H O, leads to formation of phosgene.
2
0
0
0
.3
.2
.1
FeCl3
CCl4
+
H O
2
COCl2
+
2HCl
On the other hand, this procedure cannot be applied
0.0
0
10
20
30
40
50
60
70
80
on a large scale because of its low efficiency which
is limited by the rate of water supply to prevent
deactivation of the catalyst due to transformation into
hexahydrate.
Concentration of H
2
2
O , wt %
Fig. 1. Dependence of the yield of phosgene on the concen-
tration of H O (concentration of FeCl 0.77 mol/l).
2
2
3
1
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1
404
TATAROVA et al.
Yield, mol/mol
the yield of COCl increases up to quantitative with
2
rise in the concentration of FeCl3.
0
0
0
0
0
0
0
0
0
0
.9
.8
.7
.6
.5
.4
.3
.2
.1
.0
Taking into account that a solution of hydrogen
peroxide in water with a concentration of 30 to
3
5 wt % is commercially available, in our further
experiments on studying the reaction kinetics and
mechanism we used a 35% solution of H O . The
reaction was carried out at the boiling point of the mix-
ture (i.e., at a constant temperature) with a large excess
2
2
of CCl ; the reactant concentrations were maintained
4
constant. Insofar as hydrogen peroxide is poorly
soluble in CCl , the reaction rate depends only on the
4
amount of the catalyst (FeCl ). The rate of formation
3
of phosgene linearly increases as the amount of the
catalyst rises.
The scheme of decomposition of CCl can be re-
presented as follows:
4
0
.0
0.2
0.4
0.6
0.8
, mol/l
1.0
1.2
Concentration of FeCl
3
H O
+
H O
2
Solution of H O + H O in CCl
2 2 2 4
2
2
Fig. 2. Dependence of the yield of phosgene on the concen-
tration of FeCl ; molar ratio (H O + H O )–CCl 0.347.
3 2 2 2 4
Diffusion of the reactants
to the catalyst surface
Adsorption of the reactants
on the catalyst surface
W, ml/s
Desorption
of the products
Synthesis of COCl2
1
.8
Diffusion of the products
1
1
1
1
0
0
0
0
0
.6
.4
.2
.0
.8
.6
.4
.2
.0
Taking into account that the viscosity of the mixture
is low and that the mixture is vigorously stirred due to
boiling, the reaction rate should be determined mainly
by the chemisorption and desorption processes, i.e., it
should depend only on the amount of FeCl . This
3
means that the kinetics of the process in the stationary
mode with respect to the yield of phosgene should fit
pseudozero order in the reactants, for the reaction
occurs only on the catalyst surface.
Unlike aqueous hydrolysis of carbon tetrachloride,
which follows a ionic mechanism, the reaction with
hydrogen peroxide is a radical process where H O is
0
.0
0.2
0.4
0.6
0.8
, mol/l
1.0
1.2
2
2
Concentration of FeCl
3
the primary source of radical species:
Fig. 3. Dependence of the rate of formation of phosgene (W)
on the concentration of FeCl (stationary mode).
·
H
O
2 HO
(1)
3
2
2
Hydroxyl radical reacts with carbon tetrachloride
to form hypochlorous acid and trichloromethyl radical
(
Fig. 1) and FeCl (Fig. 2). The yield of COCl linearly
3 2
increases as the hydrogen peroxide concentration rises
up to 35 wt % (Fig. 1). Further raising the H O con-
centration (to 75 wt %) leads to only slight increase in
the yield of phosgene. Simultaneously, the amount of
chlorine formed by oxidation of hydrogen chloride
increases. The intercept on the y axis corresponds to
[
reaction (2)]. Combination of the latter with hydroxyl
2
2
radical gives unstable trichloromethanol which decom-
poses to COCl and HCl [reaction (3)].
2
·
CCl
·
HO
+
CCl4
+
HOCl
COCl
(2)
3
·
·
the yield of phosgene in the hydrolysis of CCl in the
HO
+
CCl
3
[Cl
3
COH]
+ HCl
2
4
absence of hydrogen peroxide. Figure 2 shows that
(3)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 10 2004

REACTION OF CARBON TETRACHLORIDE WITH HYDROGEN PEROXIDE
1405
Hypochlorous acid is also unstable; it decomposes
with liberation of atomic oxygen [reaction (4)] which
reacts with trichloromethyl radical to give phosgene
and atomic chlorine [reaction (5)].
with primary hydroxyl radicals, which leads to hypo-
chlorous acid and atomic chlorine [reaction (15)].
·
·
HO
+
Cl2
HOCl
+
Cl
(15)
·
Hydrogen peroxide is capable of acting as both
oxidant and reducing agent, and it can decompose
along two pathways:
HOCl
HCl
+
O
(4)
(5)
·
·
·
Cl
O
+
CCl3
COCl2
+
The most probable further process is the reaction of
atomic chlorine with water, leading to regeneration of
hydroxyl radical [reaction (6)]; HO species can also
be formed by reaction of water with trichloromethyl
radical according to reaction (7).
·
HO
HO
:
:
OH
OH
2HO
(1)
H O
2
2
·
Fe2+
+
(
16)
Fe3+
·
+
HO–
+
HO
Depending on the reaction conditions, one of the
above pathways may prevail. In our case, reaction (1)
predominates, for alternative process (16) requires the
presence of an electron donor (reducing agent) in the
system [10]. Iron(II) chloride formed by reaction (8)
·
·
H O
+
Cl
HO
+
HCl
(6)
(7)
2
·
·
H O
+
CCl3
CHCl3
+
OH
2
Intermediate trichloromethanol can react with FeCl3
to give COCl and FeCl [reaction (8)]. Oxidation of
iron(II) chloride thus formed with atomic chlorine
reaction (9)] or hypochlorous acid [reaction (10)]
ensures regeneration of the catalyst.
instantaneously undergoes oxidation to FeCl via re-
3
2
2
actions (10) and (13); therefore, the concentration of
FeCl is so small that reaction (16) seems to be
2
[
improbable. Thus the formation of COCl in the pres-
2
ence of H O is a radical process, and it cannot be
2
2
regarded as a purely hydrolytic reaction.
FeCl3
+
Cl COH
COCl2
+
FeCl2
(8)
(9)
3
In order to obtain additional proofs for the radical
mechanism of the reaction under study, we examined
the effect of UV irradiation. Irradiation of the system
CCl –FeCl –H O with UV light at room temperature
·
FeCl2
+
Cl
FeCl3
·
FeCl2
+
HOCl
FeCl3
+
HO
(10)
4
3
2
2
resulted in an appreciable increase of the reaction rate,
which is typical of radical processes. Another support
for the radical mechanism is a sharp decrease in the
yield of phosgene on addition of molecular iodine or
bromine. These compounds react with radical species
Reactions (11)–(14) lead to chain termination as
a result of radical combination.
·
·
O
O
+
O2
C Cl
(11)
(12)
(13)
(14)
·
·
·
·
CCl3
CCl3
+
to give long-lived I and Br radicals. The process is
completely inhibited in the presence of atomic oxygen
2
6
·
·
Cl
+
Cl
Cl2
CCl4
(
ozone). The subsequent irradiation of the CCl4–
FeCl –H O system in the absence of other inhibitors
3
2
2
·
·
CCl3
Cl
+
leads to equilibrium between the formation of phos-
gene and its decomposition.
The above combination processes require almost
zero energy of activation, and their rates can be deter-
mined on the basis of the gas kinetic theory from the
number of double collisions. Insofar as the mobility of
oxygen atoms is much greater than that of heavier
chlorine atoms, the number of collisions (reactivity) of
atomic oxygen is much higher. Therefore, the forma-
tion of neutral oxygen molecules is more probable than
the formation of chlorine molecules. In fact, the result-
ing phosgene contains only traces of chlorine. The low
concentration of chlorine, as compared with the other
recombination products, may also be due to its reaction
3+
2+
Partial reduction of Fe to Fe and oxidation of
the latter maintains a constant concentration of radical
species on the FeCl surface, which determines the
3
pseudozero order of the reaction; i.e., the reaction rate
is proportional to the surface area of the catalyst.
Atomic chlorine and hypochlorous acid molecules
2
+
are also trapped by Fe . Therefore, the rate of phos-
gene formation is determined by two factors: the rate
3
+
2+
of formation of the Fe /Fe redox system (which
quickly comes to equilibrium) and the solubility of
hydrogen peroxide in carbon tetrachloride.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 10 2004

1
406
TATAROVA et al.
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EXPERIMENTAL
nykh produktov (Chemistry and Technology of Inter-
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Decomposition of carbon tetrachloride (I).
4
5
. Plate, N.A. and Slivinskii, E.V., Osnovy khimii i
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iron(II) chloride and 40 ml of carbon tetrachloride was
heated to the boiling point (72–73°C) on a water bath,
and 3–10 ml of a 35% aqueous solution of hydrogen
peroxide was slowly added. The evolved phosgene and
concomitant gases passed through a reflux condenser,
an empty gas-washing bottle, and a gas-washing bottle
charged with concentrated sulfuric acid into a trap
cooled to –20°C, where liquid phosgene was collected.
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washing bottle filled with aqueous ammonia. The yield
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1
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7
(
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[
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a standard procedure. The yield of COCl reached 95%
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2
(
calculated on CCl ), bp 7.56°C (760 mm) [4].
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uchenykh po khimicheskoi tekhnologii (12th Int. Conf.
of Young Scientists on Chemical Technology), Moscow,
4
Decomposition of carbon tetrachloride under
UV irradiation. The reaction was performed at room
temperature in a quartz flask which was irradiated with
a UV lamp (λ 254 nm, 250 W).
1
998, vol. 5, p. 36; Ref. Zh., Khim., 1999, no. 7N33.
1
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