Photocatalytic Conversion of a FeCl3–CCl4–ROH System

Article abstract of DOI:10.1134/S0023158417060052

The photocatalytic transformations of carbon tetrachloride and aliphatic primary alcohols in the presence of iron trichloride and a molar ratio of components FeCl₃: CCl₄: ROH = 1: 300: 2550 were studied. CCl₄ is transformed into chloroform and hexachloroethane after exposure to a mercury lamp (250 W) to the FeCl₃–CCl₄–ROH system at 20°C, whereas the primary ROH alcohols are selectively oxidized into acetals (1,1-dialkoxyalkanes). The maximum conversion of CCl₄ reaches 80%. The kinetics and mechanism of the photocatalytic conversion of the FeCl₃–CCl₄–ROH system are considered.

Full text of DOI:10.1134/S0023158417060052

ISSN 0023-1584, Kinetics and Catalysis, 2017, Vol. 58, No. 6, pp. 695–700. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © A.R. Makhmutov, 2017, published in Kinetika i Kataliz, 2017, Vol. 58, No. 6, pp. 712–717.
Photocatalytic Conversion of a FeCl3–CCl4–ROH System
A. R. Makhmutov
Bashkir State University, Birsk Branch, Birsk, 452453 Russia
e-mail: ainurmax@mail.ru
Received December 6, 2016
Abstract—The photocatalytic transformations of carbon tetrachloride and aliphatic primary alcohols in the
presence of iron trichloride and a molar ratio of components FeCl3 : CCl4 : ROH = 1 : 300 : 2550 were stud-
ied. CCl4 is transformed into chloroform and hexachloroethane after exposure to a mercury lamp (250 W) to
the FeCl3–CCl4–ROH system at 20°C, whereas the primary ROH alcohols are selectively oxidized into
acetals (1,1-dialkoxyalkanes). The maximum conversion of CCl4 reaches 80%. The kinetics and mechanism
of the photocatalytic conversion of the FeCl3–CCl4–ROH system are considered.
Keywords: carbon tetrachloride, primary aliphatic alcohols, iron trichloride, photocatalysis, 1,1-dialkoxyal-
kanes, chloroform, hexachloroethane
DOI: 10.1134/S0023158417060052
INTRODUCTION
Acetals (1,1-dialkoxyalkanes) are solvents and fra-
grances in the perfumery and food industries and they
are used as additives to medicaments in medicine. The
use of 1,1-diethoxyethane as an oxygenate additive to
motor fuels is considered promising [6].
Iron trichloride is used as a photocatalyst due to
two main reasons. Firstly, it easily oxidizes ethyl alco-
hol during irradiation by visible light [7]. Secondly,
efficiency in the Fenton reaction significantly
increases under UV irradiation (λmax = 240 nm) in its
presence due to the activation of the following stage:
Fe(H2O)3+ + hν → Fe2+ + •OH + H+ [8, 9]. In addi-
tion, FeCl3 possesses photocatalytic activity in the
aerobic oxidation processes of alkanes into alcohols
and ketones [10].
Interest in photochemical and photocatalytic pro-
cesses has increased in the past few decades. This is pri-
marily due to the prospects of creating effective artificial
systems to use solar energy [1]. An important advantage
of the photoactivation of molecules, in contrast to their
thermal activation, is that the chemical transformations
occur under relatively mild conditions, significantly
decreasing the contribution of undesirable side reac-
tions. The photocatalytic approach is also applicable to
the selective conversion of carbon tetrachloride in the
presence of aliphatic alcohols to obtain compounds that
are more in demand.
Thermal halogenation processes of alcohols with
carbon tetrachloride under the action of complex
manganese, vanadium, and molybdenum compounds
as catalysts are not selective. As a rule, the products
contain complex substances (aldehydes, ethers, esters,
acetals, and various chloroalkanes) [2, 3].
Photocatalytic conversions of CCl4 in the presence
of aliphatic primary alcohols and iron trichloride
(FeCl3–CCl4–ROH system) proceed selectively to
form three main products: chloroform, hexachlo-
roethane, and acetals (1,1-dialkoxyalkanes).
The products of photocatalytic conversion are
more in demand than the original CCl4. Chloroform,
for example, is used as a solvent and extractant; it is
also used in the production of certain dyes, pesticides,
refrigerants, etc. Detailed information on the use of
chloroform can be found in [4]. Hexachloroethane is
EXPERIMENTAL
The chemically pure initial reagents carbon tetra-
chloride, methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, amyl, and isoamyl alcohols, pyridine, and
aniline produced by EKOS-1 were preliminarily dis-
tilled according to the methods in [11, 12].
Chemically pure crystalline hydrates FeCl3 · 6H2O
(Brom, Russia) and CoSO4 · 7H2O (Splav, Russia) did
not undergo additional purification.
The photocatalytic processes were carried out on a
Photo Catalytic Reactor (Lelesil Innovative Systems,
India) with a quartz reactor of 500 mL (Stromeyer
type photoreactor with a magnetic stirrer) [13].
A GCMS-QP2010S Ultra gas chromatography-
used to obtain HFC-113 and degassing tablets in alu- mass spectrometer (SHIMADZU, Japan) equipped
minum production, it replaces in camphor nitrocellu- with a Restek Rtx-5MS column (Restek, United States)
lose plastics, and it serves as a smoke generator and having a length of 30 m and internal diameter of
intensifier of luminescence. Hexachloroethane is used 0.25 mm (the thickness of a liquid film was 0.25 μm)
in medicine to control helminths of the liver [5]. was used to identify the conversion products. The quan-
695

696
MAKHMUTOV
titative amount of 1,1-diethoxyethane was found on a nents appeared as a homogeneous brown solution.
hardware-software complex based on Kristall 5000.1
and 5000.2 chromatographs (Khromatek, Russia)
equipped with 19091F-413 HP-FFAP (Agilent Tech-
nologies, United States, 30 m × 0.32 mm, 0.25 μm) and
Analytical Science (SGE, Australia, 30 m × 0.32 mm,
0.5 μm) columns, respectively. Spectrophotometric and
kinetic analysis was performed on a UV-1800 scanning
spectrophotometer (SHIMADZU, Japan).
For a photocatalytic conversion, 1.40 mmol (378 mg)
of crystalline hydrate FeCl3 · 6H2O and 3.40 moles of
alcohol were placed into a flask-reactor. After the
complete dissolution of the crystal hydrate, 0.40 moles
(40 mL) of CCl4 was added during stirring. The loaded
reactor was connected to a photocatalytic unit as indi-
cated in the manufacturer’s instructions [13]. A mer-
cury lamp of medium pressure with a power of 250 W
was used as the radiation source. The spectral compo-
sition of the radiation was as follows (in terms of
energy): UV (48%), visible (43%), and IR (9%). The
range of lengths was 222–1368 nm. A light flux
reached the reaction system passing through an aque-
ous layer thermostated at 20°C. Photocatalytic con-
version was performed within 240 min. The liquid
phase was fractionated and analyzed after the reaction.
The dissolution of crystalline hydrate FeCl3 · 6H2O in
ethyl alcohol leads to the displacement of the crystal-
lization water by alcohol molecules from the coordi-
nation sphere of the iron ions to form iron trichloride
solvate complexes. The solvate complex has the FeCl3 ·
2C2H5OH composition [14]. Water molecules form a
C2H5OH · H2O aqua complex in excess of ethyl alco-
hol [15]. The process proceeds according to the fol-
lowing general scheme (Scheme 1):
FeCl3 · 6H2O + 8C2H5OH
excess C2H5OH
FeCl · 2C H OH + 6C H OH · H O.
⎯⎯⎯⎯⎯⎯⎯→
3
2
5
2
5
2
Scheme 1
Thus, the role is fulfilled by a FeCl3 · 2C2H5OH
photocatalyst iron trichloride solvate complex.
The addition of CCl4 does not damage the homo-
geneity of the FeCl3 · 2C2H5OH solution in ethanol.
The molar ratio of the starting components in the
reaction mixture was FeCl3 : CCl4 : C2H5OH = 1 : 300 :
2550. The irradiation of the reaction mixture for
240 min at 20°C gave a homogeneous yellow solution.
RESULTS AND DISCUSSION
Photocatalytic Conversion
Analysis of the reaction products shows that CCl4 (1)
transforms into chloroform (3) and hexachloroethane (4)
of the FeCl3–CCl4–C2H5OH Model System
The reaction mixture FeCl3–CCl4–C2H5OH during irradiation, whereas ethyl alcohol (2) is selectively
obtained after the dissolution of all the initial compo- converted to 1,1-diethoxyethane (5) (Scheme 2):
O
FeCl3, UV, 20°C
CCl4
CHCl3 + CCl3−CCl3
+
+
OH
−HCl, −H2O
O
1
2
3
4
5
Scheme 2
The molar ratio of the reaction products 3 : 4 : 5 = 2 : 1 : 3. The conversion of CCl4 reaches 56%.
Kinetics of Photocatalytic Conversion
for a FeCl3–CCl4–ROH System
presence of 3.5 mmol (1.0 g) of crystalline hydrate cobalt
sulfate CoSO4 · 7H2O. In addition, the solution acquired
an intense blue color, which indicated the exchange
According to Scheme 2, HCl is released into the reac-
tion medium after the conversion of CCl4. To detect it, reaction between HCl and a pink CoSO4 · 7H2O com-
the FeCl3 : CCl4 : C2H5OH system was irradiated in the
pound that is insoluble in ethanol (Scheme 3):
CoCl+
C2H5OH
CoCl2
CoCl3−
CoCl42−
Blue complexes soluble
in ethanol
.
CoSO4 7H2O + HCl
−H2SO4
−H2O
Pink
crystals
Scheme 3
KINETICS AND CATALYSIS
Vol. 58
No. 6
2017

PHOTOCATALYTIC CONVERSION OF A FeCl3–CCl4–ROH SYSTEM
697
tometry method in the Kinetics mode at 670 nm. For
this purpose, the samples were selected from the reac-
tor during the experiment every 30 min to measure
their optical density, which is correlated with the
degree of conversion of CCl4. Figure 1 shows the
kinetic curves of the photocatalytic conversion of CCl4
in the presence of various alcohols. These curves have
an S shape and are located on a plateau after 270 min
of the reaction. Further irradiation has no effect on the
kinetics of the reaction and the yield of the products.
Conversion depth weakly depends on the nature of the
alcohol: it slightly decreases in series CH3OH >
C2H5OH > C3H7OH > C4H9OH ≈ i-C4H9OH >
C5H11OH ≈ i-C5H11OH. This is due to an increase in
the length of the hydrocarbon fragment in aliphatic
alcohols, which affect the polarity of the reaction
medium.
80
60
40
20
Methyl alcohol
Ethanol
Propyl alcohol
Butyl alcohol
Isobutyl alcohol
Amyl alcohol
Isoamyl alcohol
0
60
120
180
240
300
Process time, min
Fig. 1. Kinetic curves of photocatalytic conversion of
FeCl –CCl –ROH system in presence of various alcohols.
3
4
Effect of Reaction Conditions on Photocatalytic
Conversion of the FeCl3–CCl4–ROH System
−
Cobalt chloride complexes CoCl+, CoCl ,
,
CoCl3
2
Chloroform (3) and hexachloroethane (4) are
and
2−are formed according to Scheme 3; they products of the photocatalytic conversion of the
CoCl4
are readily soluble in ethanol and have an intense blue
FeCl3–CCl4–ROH system in methyl (6), propyl (7),
butyl (8), isobutyl (9), amyl (10), and isoamyl (11)
alcohols, whereas 1,1-dialkoskialcanes 12–17 con-
color with an absorption maximum at 670 nm [16].
The colored cobalt complexes made it possible to
clearly study the kinetics of the process with the pho- form to the initial alcohols (Scheme 4):
R'
O
FeCl3, UV, 20°C
CHCl3 + CCl3−CCl3 + R'
CCl4
+
ROH
−HCl; −H2O
O
R'
6−11
12−17
(R = CH3– (6), C3H7– (7), C4H9– (8), i-C4H9– (9), C5H11– (10), i-C5H11– (11);
R′ = H– (12), C2H5– (13), C3H7– (14), i-C3H7– (15), C4H9– (16), i-C4H9– (17))
Scheme 4
The molar ratio of the reaction products 3 : 4 : 12– to 70°C changes both the rate of the process and the
17 is 2 : 1 : 3. The conversion of CCl4 slightly decreases nature of the dependence, which is due to the
increased effect of thermal processes on the conver-
sion of CCl4. Analysis of the reaction mass under the
conditions on thermal conversion of the FeCl3–
CCl4–C2H5OH system (70°C, 240 min, and without
irradiation) showed that the chlorination products of
ethyl alcohol, acetaldehyde, ethyl acetate, acetic
acid, and acetal, as well as compounds 3 and 4 and
pentachloroethane (products of the CCl4 transfor-
mation), are formed. Thus, the simple thermal con-
version of the FeCl3–CCl4–C2H5OH system pro-
ceeds as an unselective process to form complex reac-
tion products.
as the hydrocarbon moiety of alcohol increases from
64% for methanol to 49% for amyl alcohol. Chlorina-
tion products of the oxidized alcohols (aldehydes,
acids, and ethers) formed together with the main
products of photocatalytic conversion in systems with
alcohols 8, 9, 10, and 11, whose total yield was 5–8%.
When the length of hydrocarbon fragments increases,
the probability of chlorination also increases.
The temperature effect on the photocatalytic con-
version of the FeCl3–CCl4–ROH system was studied
on the FeCl3–CCl4–C2H5OH model system in the
presence of CoSO4 · 7H2O (Fig. 2). The shape of the
kinetic curves remains significantly unchanged at
10–40°C. However, the increase in temperature up
The effect of pyridine and distilled water on the
photocatalytic conversion of CCl4 and the yield of the
KINETICS AND CATALYSIS Vol. 58 No. 6 2017

698
MAKHMUTOV
nation products of oxidized forms of alcohol (alde-
100
80
60
40
20
70°С
60°С
50°С
40°С
30°С
20°С
10°С
hydes, acids, and ethers). The fact that pyridine is used
as an additive is due to its basic nature, because it binds
the acids formed after the photocatalytic process
(HCl, etc.) and thereby prevents the formation of a
complex between the acids and iron ions. There are
data which confirm the inhibitory effect of acids on
the photocatalytic activity of iron ions in the Fenton
photoreaction [17]. Other bases (for example, alkalis)
disrupt the homogeneity of the system to form a pre-
cipitate of iron hydroxides, so that photocatalytic con-
version does not occur in this case.
The addition of distilled water of up to 30% to the
FeCl3–CCl4–C2H5OH system (experiments 5, 6,
and 7) does not disrupt their homogeneity and slightly
increases the conversion of CCl4, which makes it pos-
sible to use the more easily available aqueous alcohol
mixtures in the photocatalytic conversion process.
0
60
120
180
240
300
Process time, min
Fig. 2. Effect of temperature on photocatalytic conversion
of FeCl –CCl –C H OH system.
3
4
2
5
products is given in Table 1. As can be seen, the addi-
tion of 0.12 mol (10 mL) of pyridine to the reaction
medium increases the conversion of CCl4 with the
methanol system to 80% (Table 1, experiment 2). As a
Mechanism of Photocatalytic Conversion
of the FeCl3–CCl4–C2H5OH System
As mentioned above, the solvate complex of iron tri-
result, the yield of the reaction products also chloride FeCl3 · 2C2H5OH fulfills the role of a photo-
increases. The molar ratio of the products 3 : 4 : 5, 12,
14, 16 remains unchanged at 2 : 1 : 3. In systems with
alcohols 8 and 10 (Table 1, experiments 9 and 11), the
catalyst in the FeCl3–CCl4–C2H5OH system. Absorb-
ing a UV radiation quantum, it passes into the electron-
excited state [FeCl3 · 2C2H5OH]* and easily oxidizes
addition of pyridine decreases the yield of the chlori- ethyl alcohol into acetal 5 (Scheme 5, stage 2):
Table 1. Effect of pyridine and water on photocatalytic conversion of FeCl3–CCl4–ROH system
Composition of products, mol %
Mole ratio of components
Conversion
No. exp Alcohol
chlorination
products
FeCl3 : CCl4 : ROH : С6H5N : H2O of CCl4, %
CHCl3
C2Cl6
acetal
1
2
CH3OH
CH3OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C2H5OH
C4H9OH
C4H9OH
C5H11OH
C5H11OH
1 : 300 : 2550 : 0 : 0
1 : 300 : 2550 : 85 : 0
1 : 300 : 2550 : 0 : 0
1 : 300 : 2550 : 85 : 0
1 : 300 : 2550 : 0 : 500
1 : 300 : 2550 : 0 : 2000
1 : 300 : 2550 : 0 : 3500
1 : 300 : 2550 : 0 : 0
1 : 300 : 2550 : 85 : 0
1 : 300 : 2550 : 0 : 0
1 : 300 : 2550 : 85 : 0
64
80
56
66
57
59
60
52
59
49
56
34
32
31
30
29
37
33
24
32
30
33
18
17
20
17
19
15
16
16
16
14
16
48
51
49
53
52
48
51
55
52
48
51
–
–
–
–
–
–
–
5
3
4
5
6
7
8
9
–
8
10
11
–
Dashes mean that there are no chlorination products.
KINETICS AND CATALYSIS
Vol. 58
No. 6
2017

PHOTOCATALYTIC CONVERSION OF A FeCl3–CCl4–ROH SYSTEM
699
hν
.
.
[FeCl3 2C2H5OH]*
(1)
(2)
FeCl3 2C2H5OH
O
O
Excess of C2H5OH
.
.
2[FeCl2 C2H5OH] +
2[FeCl3 2C H OH]*
+ C2H5OH
2
5
−2HCl; −H2O
.
2FeCl3
2FeCl3 2C2H5OH
O
O
.
(3)
(4)
2[FeCl2 C H OH]
+ 4CCl4
2FeCl3 + C2Cl6 + 2CHCl3 + 2
2
5
−2HCl; −H2O
C2H5OH
FeCl3 2C2H5OHExcess of
.
FeCl3 2C2H5OH
+
Scheme 5
It is well known that acetals are obtained by the
interaction between alcohols and aldehydes [18].
CONCLUSIONS
In summary, studying the photocatalytic conver-
sion of the FeCl3–CCl4–ROH system showed that
CCl4 is transformed into chloroform and hexachlo-
roethane under the action of medium-pressure mer-
cury lamp radiation at 20°C, whereas the primary
ROH alcohols are selectively oxidized to 1,1-dialkoxy-
alkanes. The addition of pyridine and water affects the
conversion of CCl4, so that the maximum conversion
of CCl4 reaches 80%. The kinetics of the process were
studied in the presence of colored cobalt complexes
and a probable mechanism of the photocatalytic con-
version of the FeCl3–CCl4–ROH system was pro-
posed.
Acetaldehyde is formed during the oxidation of
ethyl alcohol with iron trichloride [7]. To detect free
acetaldehyde as a stable intermediate of the photo-
catalytic reaction, aniline was added to the FeCl3–
CCl4–C2H5OH system. Analysis of the reaction
products in this model system showed that the pres-
ence of chloroform (3), hexachloroethane (4), and
1,1-diethoxyethane (5); however, Schiff bases and
condensation products obtained after the interaction
between acetaldehyde and aniline were not observed.
Thus, it can be assumed that free acetaldehyde is not
formed in the system studied.
The photooxidation of ethanol was carried out with
iron trichloride at a ratio of FeCl3 : C2H5OH = 1 : 2550
without CCl4. The quantitative chromatographic
analysis of the solution after the reaction showed that
the amount of 1,1-diethoxyethane is 3.3 × 10–3 mol/L,
whereas the concentration of iron trichloride
decreases from 7.0 × 10–3 to 4.4 × 10–4 mol/L accord-
ing to the photometric data. Consequently, two moles
of iron trichloride is reduced to form a mole of acetal
(Scheme 5, step 2).
REFERENCES
1. Yuana, L., Hana, Ch., Yanga, M.-Q., and Xu, Y.-J.,
Int. Rev. Phys. Chem., 2016, vol. 35, no. 1, p. 1.
2. Khusnutdinov, R.I., Shchadneva, N.A., Baiguzina, A.R.,
Lavrent’eva, Yu.Yu., and Dzhemilev, U.M., Izv. Akad.
Nauk, Ser. Khim., 2002, no. 11, p. 1919.
3. Khusnutdinov, R.I., Shchadneva, N.A., Burangu-
lova, R.Yu., Muslimov, Z.S., and Dzhemilev, U.M.,
Zh. Org. Khim., 2006, vol. 42, no. 11, p. 1629.
4. Bandman, A.L., Voitenko, G.A., Volkova, N.V., et al.,
Vrednye khimicheskie veshchestva. Uglevodorody. Galo-
genproizvodnye uglevodorodov (Harmful Chemicals.
Hydrocarbons. Halogen Derivatives of Hydrocarbons),
Leningrad: Khimiya, 1990.
5. Knunyants, I.L., Khimicheskaya entsiklopediya (Chem-
ical Encyclopedia), Moscow: Sovetskaya Entsiklope-
diya, 1988, vol. 1.
The oxidation of the intermediate two-valence iron
complex FeCl2 · C2H5OH proceeds under the action
of CCl4 (Scheme 5, step 3). The whole complex is oxi-
dized, i.e., the two-valence iron ion and ethanol mol-
ecule are in it. As a result, iron trichloride returns to
the reaction medium, whereas oxidized ethanol reacts
with the FeCl3 · 2C2H5OH complex to form acetal 5.
Chloroform 3 and hexachloroethane 4 are reduction
products of CCl4.
6. Vil’danov, F.Sh., Latypova, F.N., Chanyshev, R.R.,
Daminev, R.R., Karimov, O.Kh., and Mamlieva, A.V.,
Bashkirskii Khim. Zh., 2013, vol. 20, no. 3, p. 145.
7. Karyakin, Yu.V. and Angelov, I.I., Chistye khimicheskie
veshchestva (Pure Chemical Substances), Moscow:
Khimiya, 1974.
Iron trichloride FeCl3 coordinates new ethanol
molecules in the reaction medium, so that the catalyt-
ically active form of the FeCl3 · 2C2H5OH (Scheme 5,
step 4) solvate complex is reduced.
8. Feng, W. and Nansheng, D., Chemosphere, 2000,
vol. 41, p. 1137.
KINETICS AND CATALYSIS Vol. 58 No. 6 2017

700
MAKHMUTOV
9. Ruppert, G. and Bauer, R., J. Photochem. Photobiol. A.: 15. Dolenko, T.A., Burikov, S.A., Patsaeva, S.V., and
Chemical, 1993, vol. 73, p. 75.
Yuzhakov, V.I., Kvantovaya Elektron., 2011, vol. 41,
no. 3, p. 267.
10. Takaki, K., Yamamoto, J., Komeyama, K., Kawabata, T.,
and Takehira, K., Bull. Chem. Soc. Jpn., 2004, vol. 77,
p. 2251.
11. Bekker, H., Berger, W., and Domschke, G., Organicum:
Practical Handbook of Organic Chemistry, New York:
Pergamon, 1973.
12. Vaisberger, A., Proskauer, E., Riddik, D., and Tups, E.,
Organicheskie rastvoriteli (Organic Solvents), Moscow:
IL, 1958.
16. Pyatnitskii, I.V., Analiticheskaya khimiya kobal’ta
(Analytical Chemistry of Cobalt), Moscow: Nauka,
1965.
17. Kuznetsova, E.V., Cand. Sci. (Chem.) Dissertation,
Novosibirsk: Boreskov Institute of Catalysis, Russian
Academy of Sciences, 2005.
18. Vollhardt, K., Peter, C., and Schore, N.E., Organic
Chemistry: Structure and Function, New York:
W.E. Freeman and Company, 2007.
13. http://www.lelesil.in.
14. Furman, A.A., Neorganicheskie khloridy (Inorganic
Translated by A. Tulyabaev
Chlorides), Moscow: Khimiya, 1980.
KINETICS AND CATALYSIS
Vol. 58
No. 6
2017