Catalytic properties of polymer matrix-immobilized cobalt complexes with sulfonated phthalocyanines

Article abstract of DOI:10.1134/S0965544113030122

Enhancement of the catalytic activity of phthalocyanine catalysts by their immobilizing on polymer matrices has been studied. It has been found that the immobilization of sulfonated cobalt phthalocyanines on polymers enhances their catalytic activity in the oxidation of sodium diethyldithiocarbamate with air oxygen under mild conditions.

Full text of DOI:10.1134/S0965544113030122

ISSN 0965ꢀ5441, Petroleum Chemistry, 2013, Vol. 53, No. 3, pp. 197–200. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.S. Vashurin, R.A. Badaukaite, N.A. Futerman, S.G. Pukhovskaya, G.P. Shaposhnikov, O.A. Golubchikov, 2013, published in Neftekhimiya, 2013, Vol. 53,
No. 3, pp. 221–225.
Catalytic Properties of Polymer MatrixꢀImmobilized Cobalt
Complexes with Sulfonated Phthalocyanines
A. S. Vashurin, R. A. Badaukaite, N. A. Futerman, S. G. Pukhovskaya,
G. P. Shaposhnikov, and O. A. Golubchikov
Ivanovo State University of Chemistry and Technology, Ivanovo, Russia
eꢀmail: asv_87@mail.ru
Received September 26, 2012
Abstract—Enhancement of the catalytic activity of phthalocyanine catalysts by their immobilizing on polyꢀ
mer matrices has been studied. It has been found that the immobilization of sulfonated cobalt phthalocyaꢀ
nines on polymers enhances their catalytic activity in the oxidation of sodium diethyldithiocarbamate with
air oxygen under mild conditions.
Keywords: catalysis, phthalocyanines, complexes, polymer matrix
DOI: 10.1134/S0965544113030122
An effective way of desulfurization of petroleum substance, a representative of the RꢀSH class of comꢀ
fractions is catalytic oxidation of mercaptans in aqueꢀ pounds.
ous alkali media to form dialkyl disulfides, which can be
isolated in pure form suitable for further use [1–3]. In
the petrochemical industry, cobalt complexes of phthaꢀ
EXPERIMENTAL
Cobalt complexes of tetraꢀ4ꢀsulfophthalocyanine
I) and tetraꢀ4ꢀ[(6',8'ꢀdisulfoꢀ2ꢀnaphthyl)oxy]phthaloꢀ
locyanines are widely used as active catalysts for mild
oxidation of mercaptans and hydrogen sulfide [2–6]. In
the homogeneous mode of catalysis, waterꢀsoluble salts
of sulfonated and carboxylated metal phthalocyanines
are used. A significant drawback of ionic phthalocyaꢀ
nine compounds is their tendency to associate in soluꢀ
tion at relatively low concentrations [7–12], which
reduces their catalytic activity and, therefore, limits the
effective practical use.
(
cyanine (II) in the form of sodium salts were prepared
from the corresponding phthalonitriles and anhydrous
cobalt chloride by template synthesis with heating. The
structure of the product compounds was characterized
by IR and electronic absorption spectroscopy and eleꢀ
mental analysis. The phthalocyanines are green powꢀ
ders well soluble in water, a DMF/water mixture,
DMSO, and aqueous alkali. Found for II, %: C 48.3,
In this study we investigated the catalytic activity of H 2.2, N 6.2, S 14.4. Calculated for C H N S O Со
,
72
40
8
8
ν
28
–1
cobalt complexes of sulfonated phthalocyanines, %: C 48.5, H 2.2, N 6.3, S 14.3. IR spectrum,
cm :
S=O), 1210 ( Ar–O–Ar)
immobilized on the surface of a polymer support, in the 1039 (
ν
s
S=O), 1103 (
ν
ν
as
oxidation of sodium diethyldithiocarbamate as a model [13].
R
R
N
SO Na
3
N
N
N
N
I: R = SO Na,
3
N
Co
N
N
R
SO Na
3
II: R
=
O
R
The support used was a commercial nonwoven made age molecular mass of 20 000 and a density of 203 g/m2.
from poly(ethylene terephthalate)–poly(methyl methꢀ The polymer was activated in a 350ꢀW microwave
acrylate) (PMMA) (Russia). The PMMA has an averꢀ device for three minutes.
197

1
98
VASHURIN et al.
Cobalt phthalocyanine complexes were immobiꢀ liminarily obtained calibration curve relating the absorꢀ
lized onto the copolymer by deposition from aqueous bance of the solution to the DTC concentration was
–5
solutions with a concentration of ~5
nonwoven sample of cm in size was immersed in 10 to
00 mL of a phthalocyanine solution, held for 2–4 h at = (32.55
, and freed of the solvent by evaporation. The samꢀ 0.999 in agreement with the published data [19]. The
ple was washed by holding for 40 min in 100 mL of disꢀ electronic absorption spectra were recorded with a Shiꢀ
tilled water and then slowly dried at 40 . The amount madzu UV 1800 dualꢀbeam spectrophotometer in
× 10 mol/L. A used, which was linear in the concentration range of 5 ×
–3
–2
5
×
5
3
×
10 mol/L and described by the equation:
0.01) with a correlation coefficient of
1
y
±
x
25°С
°С
of the immobilized complex was monitored by followꢀ quartz cells with an optical path length of 10 mm.
ing electronic absorption spectra (EAS) of the washing
solutions.
The electronic absorption spectrum of compound II
immobilized on PMMA was recorded by immersing
nonwoven samples in quinoline, as its refractive index is
almost the same as that of PMMA. Thus, light scatterꢀ
ing by the nonwoven was reduced to a minimum.
Reagentꢀgrade copper sulfate used as a source of
central ion in the analytical determination of sodium
diethyldithiocarbamate was preliminarily purified by
recrystallization from aqueous solution and dried at
RESULTS AND DISCUSSION
Examination of the electronic absorption spectra of
solutions of phthalocyanine II (Fig. 1a) in a wide conꢀ
centration range showed that the macrocycle exists in
–4
associated state in the concentration range of
2
×
10
–5
–1
to
3 × 10 mol L . Further dilution of the solutions
displaces the monomer–dimer equilibrium toward the
monomer; however, we failed to record the spectrum of
the monomeric form because of a low value of its molar
absorption coefficient at the Qꢀband.
105°С [14]. Sodium diethyldithiocarbamate (DTC) of
the special purity grade was used as received.
Chloroform used for extraction was purified accordꢀ
Figure 1b shows the change in the electronic absorpꢀ
ing to the wellꢀknown procedure: washed with distilled tion spectrum of an aqueous phthalocyanine II solution
water to remove the stabilizer, dried by passing through during its titration with pyridine. As can be seen, the
an alumina column, and then subjected to fractional introduction of pyridine into the system results in gradꢀ
distillation [15].
The oxidation reaction of sodium diethyldithiocarꢀ a rise in the intensity of the Qꢀband at 675 nm correꢀ
ual reduction in the absorption intensity at 630 nm and
–
3
–3
bamate (concentration of 2.7
× 10 –8.3 ×
10 mol/L sponding to the monomeric state of the macrocycle.
in aqueous solution) was studied in a lightꢀprotected, The isosbestic points are retained during the titration of
thermostated 50ꢀmL cell at 298.15
0.05 K. The the phthalocyanine II solution with pyridine. The longꢀ
±
experiments were performed at pH 7.6, since it has been wavelength absorption band undergoes a bathochromic
found [16, 17] that the process has the maximum rate shift by 8 nm, indicating the axial coordination of pyriꢀ
under these conditions. The setup used in the work conꢀ dine by the monomeric form of the phthalocyanine
sisted of a thermostat, the temperatureꢀcontrolled cell complex in accordance with the equation:
with allowance for sampling, and an oxygen supply unit.
(
СоРс) + 2 Ру
2 СоРсРу.
Before starting the experiment, a control sample was
collected. Next, the catalyst was added to the solution (a
blank, catalystꢀfree run was also conducted) and air
began to be supplied through a capillary to the cell. The
onset time of air supply was taken as the beginning of
the reaction. During the entire course of the run, 2ꢀmL
samples were taken at regular intervals to determine the
current DTC concentration.
2
Similar results were obtained in the study of the conꢀ
centration dependence of the electronic absorption
spectrum of phthalocyanine I. These data show that the
absorption spectra of I and II depend on both the conꢀ
centration and the form of existence of the macrocycles
in solution.
The DTC determination procedure was as follows:
The experimental data (Fig. 2) show that a hybrid
the test solution was sampled to take 2 mL with the inteꢀ material can be obtained by immobilization of I and II
grated capillary, and 4 mL of 0.2 M copper sulfate soluꢀ on the chemically activated copolymer surface. Note
tion was added to maintain an excess of copper ions that a certain portion of immobilized I or II is associꢀ
with respect to DTC. It is known that DCT forms a ated with the support surface via weak nonspecific
waterꢀinsoluble complex by reacting with copper ions interactions. To determine the quality of immobilizaꢀ
[
18]. The electronic absorption spectrum of the copper tion, heterogeneous catalyst samples were repeatedly
complex dissolved in chloroform displays a band at extracted with distilled water until a colorless extract.
40 nm, thereby allowing for spectral monitoring of the Judging by electronic absorption spectra of aggregated
λ
=
4
current concentration of DTC in the solution [19]. The water extracts, about 65% of the catalyst is fixed on the
resulting precipitate was dissolved in 5 mL of chloroꢀ copolymer surface. Thus, the surface of the samples
form, 2 mL of the complex solution was diluted with that were further tested in the catalytic process had conꢀ
–6
5
mL of chloroform, and the absorbance of the solution tained ~3.25 × 10 mol of fixed I or II. The obtained
at a wavelength of 440 nm was measured to further calꢀ materials were used as heterogeneous catalysts in the
culate the DTC concentration. For this purpose, a preꢀ diethyldithiocarbamate oxidation reaction:
PETROLEUM CHEMISTRY Vol. 53
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2013

CATALYTIC PROPERTIES OF POLYMER MATRIXꢀIMMOBILIZED COBALT
199
(
b)
(
а)
Α
1
Α
0
0
0
0
0
0
.13
0
.12
.11
.09
.07
.05
.03
0
.08
2
0.04
400
500
600
700
800
, nm
450
550
650
750
850
, nm
λ
λ
Fig. 1. Concentration dependence of the electronic absorption spectra of (a) phthalocyanine II at (
1
)
2
×
10–4 and (
с = 1.1 × 10 mol L during titration with pyridine to
2) 8 ×
–
6
mol L–1 and (b) an aqueous solution of phthalocyanine II with
–4
–1
1
0
a molar ratio of 1 : 2.
C H
S
–
S
C H
S
S
S
S
C H
2
2
5
2
5
5
5
O , Kat
2
Na+
N
C
N
C
C
N
–NaOH
C H
C H
2
C H
2
2
5
5
А
Providing that oxygen and catalyst concentrations in
the solution are constant, the rate of the DCT oxidation
1
reaction is described by the firstꢀorder rate law: dc
/dt =
–
kapp , where is the DTC concentration, is the time,
⋅
c
с
t
0.12
–1
and kapp is the reaction rate constant in s . This is conꢀ
2
firmed by invariability of the apparent DTC oxidation
rate constants calculated by the equation kapp
1/ )ln(c0 ), where с0 is the initial concentration of
DTC and is the current DTC concentration at a time t.
=
(
t
/
c
c
0.10
0.08
0.06
The noncatalytic oxidation of DTC on activated
PMMA proceeds very slowly, as evidenced by a low
value of the apparent reaction rate constant kapp
=
–5 –1
1.7 × 10 s .
Maizlish and Shaposhnikov [20] found that I is quite
an effective catalyst for the oxidation of DTC; however,
complex I can be used only in a narrow concentration
range because of the association.
0.04
3
In this study we have shown that the DTC oxidation
efficiency increases in the presence of phthalocyanine
catalysts immobilized in a polymer matrix. Thus, kapp
=
–4
–4 –1
0.02
2.3 × 10 or 4.6 × 10 s for the catalyst based on
immobilized complex I or II, respectively. Comparꢀ
ing the data on catalysis under the same conditions
by an aqueous solution of I with a concentration of
5
50
600
650
700
λ
, nm
Fig. 2. Electronic absorption spectrum of the catalyst (II):
) immobilized on the PMMA copolymer, ( ) aqueous
10 mol/L, and (
extract after washing the modified polymer.
–
5
–4 –1
5
× 10 mol/L (kapp = 0.8 × 10 s ) [16], we can conꢀ
(1
2
clude that the deposition of I on the polymer increases
its catalytic activity by a factor of 2.5 and the activity of
II is increased by more than fivefold by immobilization.
–5
solution with a concentration of
5
×
3)
PETROLEUM CHEMISTRY Vol. 53
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2013

200
VASHURIN et al.
–
4
–1
trations of Co phthalocyanine). As follows from these
kapp × 10 , s
2
data, phthalocyanines I and II fixed to the polymer supꢀ
port are quite effective catalysts over a wide concentraꢀ
tion range.
8
6
4
2
For the heterogeneous catalyst based on II, its activꢀ
ity in a series of successive experiments was investigated.
Figure 4 shows the change in the apparent rate constant
for the oxidation of DTC, depending on the number of
oxidation cycles.
Despite a slight decrease in kapp for the oxidation of
diethyldithiocarbamate, it can be stated that tetraꢀ4ꢀ
1
[
(6',8'ꢀdisulfoꢀ2ꢀnaphthyl)oxy]phthalocyanine
(II)
immobilized on PMMA is an efficient catalyst for oxiꢀ
dation of RSH compounds with atmospheric oxygen in
alkaline solutions.
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1
1
5
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Figure 3 shows estimates of the catalytic efficiency
of DTC oxidation, depending on the amount of the catꢀ
alyst (deposited from solutions with different concenꢀ
2
PETROLEUM CHEMISTRY Vol. 53
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2013