Catalytic activity of iron-containing polymers in hydroxylation of benzene with hydrogen peroxide

Article abstract of DOI:10.1134/S1070363207050167

Hydroxylation of benzene with hydrogen peroxide in aqueous acetonitrile at 50°C was studied. The KU-2-8 and KU-1 cation exchangers, and also specially synthesized cation exchangers and phenolformaldehyde resins derived from pyrocatechol and resorcinol, al

Full text of DOI:10.1134/S1070363207050167

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 5, pp. 911 914.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
No. 5, pp. 815 818.
N.I. Rudakova, M.V. Klyuev, Yu.G. Erykalov, D.N. Ramazanov, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77,
Catalytic Activity of Iron-containing Polymers
in Hydroxylation of Benzene with Hydrogen Peroxide
N. I. Rudakova, M. V. Klyuev, Yu. G. Erykalov, and D. N. Ramazanov
Ivanovo State University, ul. Ermaka 39, Ivanovo, 153025 Russia
e-mail: klyuev@ivanovo.ac.ru
Received July 27, 2006
Abstract Hydroxylation of benzene with hydrogen peroxide in aqueous acetonitrile at 50 C was studied.
The KU-2-8 and KU-1 cation exchangers, and also specially synthesized cation exchangers and phenol
formaldehyde resins derived from pyrocatechol and resorcinol, all modified with Fe(III) cations, were used as
catalysts. The macrocomplex KU-2-8/Fe3+ showed the highest catalytic activity and ensured 32% yield of
phenol in 15 min. The formation of phenol depends in a complex fashion on the initial concentration of
hydrogen peroxide, content of Fe(III) ions in the polymer, and reaction time.
DOI: 10.1134/S1070363207050167
The presently used procedures for production of
phenol from benzenesulfonic acid, chlorobenzene, and
cumene are multistep and power-consuming; further-
more, they involve formation of by-products requiring
utilization [1].
cation exchangers derived from pyrocatechol (III) and
resorcinol (IV), and also with pyrocatechol formalde-
hyde (V) and resorcinol formaldehyde (VI) resins.
It was found (Table 1) that the KU-2-8 resin absorbed
the largest amount of Fe(III) cations [m(Fe3+) =
0.068 g of Fe3+ per gram of polymer], forming a
macrocomplex with Fe(III) via sulfo groups. The pres-
ence in polymers III VI of phenolic hydroxyls or of
hydroxy and sulfo groups simultaneously (polymer II)
leads to a decrease in the absorption capacity for
Fe(III) by a factor of 2 3, to 0.021 0.030 g of Fe3+
per gram of the polymer.
Therefore, much researchers’ attention is given today
to the development of one-step methods of phenol
synthesis, based on direct oxidation of benzene with
oxygen or substances acting as oxygen donors (N2O,
H2O2, etc.); from the viewpoint of ecology, H2O2 is
preferable. In particular, high yield of phenols (up to
80%) was attained in [2] in hydroxylation of benzene
with hydrogen peroxide:
Hydroxylation experiments were performed in
aqueous acetonitrile at 50 C (Table 1).
C6H6 + H2O2
C6H5OH + H2O.
The highest yield of phenol was observed in the
presence of catalyst I/Fe3+ (run no. 1, Table 1). The
macrocomplex of Fe(III) with polymer VI showed no
catalytic properties in the hydroxylation. We exam-
ined how the phenol yield is influenced by the reac-
tion time, initial concentration of hydrogen peroxide,
and mass of the catalyst (I/Fe3+). The results are given
in Table 2.
The reaction occurs under mild conditions: aqueous
phase, 20 80 C, catalysts cetyltrimethylammonium
bromide and Fe(II) and Fe(III) cations. Karakhanov
et al. [3, 4] used as benzene hydroxylation catalysts
macrocomplexes of Fe(III) with polyethers containing
a pyrocatechol core. The maximal yield of phenol
(aqueous acetonitrile, 50 C, 1 h) was 30%. It was
shown that the phenol yield could be increased to
43% by performing the reaction in acetonitrile at 50 C
for 2 h under the conditions of homogeneous catalysis
with iron(II) sulfate. Under similar conditions, with
a 1 : 1 mixture of Fe2(SO4)3 9H2O + CuCl, the yield
of phenol reached 48% in 3 h [5].
The experiment showed that the dependences of the
phenol yield on the reaction time, initial concentration
(C0) of H2O2, and mass (m) of Fe3+ have maxima.
These results are consistent with the views, commonly
accepted today, that catalytic oxidation of benzene in
aqueous solution is a radical ion reaction in which
phenol is an intermediate [6]. Table 2 clearly shows
that the maximal yield of phenol (Pmax, %) is attained
in different times depending on the ratio of the initial
concentration of hydrogen peroxide and mass of Fe3+
In this study we examined hydroxylation of ben-
zene in the presence of iron(III) complexes with KU-
2-8 (I) and KU-1 (II) cation exchangers, with sulfonic
911

912
RUDAKOVA et al.
Table 1. Hydroxylation of benzene in aqueous acetonitrile at 50 C in the presence of iron-containing polymers
C0, M
m(Fe3+),
Time,
min
Phenol
yield, % mol g 1 min
TN 104, a
Run no. Polymer
1
g
C6H6
1.22
H2O2
1.14
CH3CN
13.90
H2O
8.46
1
2
I
I
0.067
0.030
0.024
15
30
60
30
60
32.1
11.2
5.5
1.6
3.2
1.3
5.6
8.6
11.5
4.4
6.7
9.7
3.9
2.4
3.7
106
18.7
3
I
4.6
6.0
6.0
1.6
8.7
10.0
10.7
3.4
9.8
11.4
3.8
4
II
1.28
1.28
1.30
1.30
15.23
15.23
6.35
6.35
5
II
6
II
90
90
7
8
9
10
11
12
13
14
15
III
III
III
III
IV
IV
IV
V
120
150
180
120
150
180
60
0.019
0.038
1.28
1.22
1.30
1.56
15.23
13.93
6.35
8.46
3.5
3.6
V
90
a
(TN) Turnover number, i.e., amount of phenol (mol) formed in unit time (1 min) per gram of the catalyst.
Table 2. Hydroxylation of benzene in aqueous acetonitrile at 50 C in the presence of catalyst I/Fe3+. Initial concentra-
tions, M: C6H6 1.22, CH3CN 13.9, and H2O 8.46
C0(H2O2)/m(Fe3+),
Run no.
C0(H2O2), M
m(Fe3+), g
Time, min
Phenol yield, %
1
mol l 1 g
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
1.56
0.067
23.3
15
30
60
90
15
30
60
90
110
15
30
60
90
15
30
60
15
30
60
90
12.8
12.9
7.8
7.9
5.7
6.7
9.6
11.7
12.6
1.8
3.9
5.7
13.6
32.1
11.2
5.5
1.56
1.56
0.043
0.017
36.3
91.8
1.14
1.01
0.067
0.038
17.0
26.6
8.8
10.8
12.9
9.9
on the polymeric support: f = C0(H2O2)/m(Fe3+),
increase in f to 23.3 and 26.6 led to a decrease in the
maximal yield of phenol to 12.9% (at reaction times
of 30 and 60 min, respectively). When the reaction
1
mol l 1 g . The maximal yield of phenol, 32.1%, was
attained at f = 17.0 and reaction time of 15 min. An
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 5 2007

CATALYTIC ACTIVITY OF IRON-CONTAINING POLYMERS
913
was performed for 15 min, a linear correlation bet-
ween the reciprocal phenol yield 1/P and f was ob-
served:
Table 3. Comparison of the experimental and calculated
yields of phenol (reaction time 15 min)
1
f, mol l 1 g
Pexp, %
Pcalc, %
2
1/P = 0.7 10
f
0.081.
(1)
17.0
23.3
26.6
36.3
91.8
32.1
12.8
8.8
5.7
1.8
26.6
12.3
9.5
5.8
1.8
After a transformation, we obtain
P = 12.3/(0.086f 1).
(2)
The phenol yields in 15 min, obtained experimen-
tally and calculated by formula (2), are reasonably
consistent (Table 3).
Cation exchangers III and IV were prepared by sul-
fonation of pyrocatechol and resorcinol, followed by
condensation of the sulfonic acids with formaldehyde
by the procedure in [7]. Polymers V and VI were
prepared by condensation of the corresponding
phenols with formaldehyde in accordance with [7].
EXPERIMENTAL
Analysis for phenol was performed with a Model
3700 chromatograph (Russia) equipped with a flame
ionization detector. A stainless steel column (1 m
2 mm) was packed with 5% XE-60 on Chezasorb AW
(0.20 0.36 mm). The oven temperature was 90 C.
The concentration of hydrogen peroxide was deter-
mined by iodometric titration [8]. Acetonitrile and
benzene were purified by procedures suggested in [9].
The other chemicals were of no less than pure grade
and were used as received.
1
The carrier gas was helium (1.8 l h ). The error of
phenol determination was 2%.
Hydroxylation of benzene. A three-necked flask
was charged with acetonitrile, benzene, and a weighed
portion of a catalyst. The mixture was heated to 50 C,
and an aqueous solution of hydrogen peroxide was
gradually added. Samples of the reaction mixture were
taken at definite intervals and quenched by adding a
dilute alkali solution to quickly decompose unchanged
hydrogen peroxide and convert the phenol into phen-
olate. The subsequent treatment of the samples con-
sisted in vacuum evaporation of acetonitrile and ben-
zene, acidification of the mixture, and extraction of
phenol with diethyl ether. The extract was analyzed
by GLC using naphthalene as internal reference.
ACKNOWLEDGMENTS
The study was financially supported by the Minis-
try of Education and Science of the Russian Federa-
tion (project RNP.2.2.1.1.7181).
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