Solid-phase synthesis and catalytic sweetening performance of sulfonated cobalt phthalocyanine from sulfonated phthalic anhydride mixture

Article abstract of DOI:10.1039/c3nj01063e

A relatively green, efficient and economical synthetic route for the one-step solid-phase synthesis of sulfonated cobalt phthalocyanine from sulfonated phthalic anhydride mixture was studied, and could solve the serious problems of waste acid pollution an

Full text of DOI:10.1039/c3nj01063e

NJC
View Article Online
View Journal | View Issue
PAPER
Solid-phase synthesis and catalytic sweetening
performance of sulfonated cobalt phthalocyanine
from sulfonated phthalic anhydride mixture
Cite this: New J. Chem., 2014,
3
8, 663
Lijun Zhu, Xiaohui Jing, Lechun Song, Bin Liu, Yulu Zhou, Yuzhi Xiang and
Daohong Xia*
A relatively green, efficient and economical synthetic route for the one-step solid-phase synthesis of
sulfonated cobalt phthalocyanine from sulfonated phthalic anhydride mixture was studied, and could solve the
serious problems of waste acid pollution and the low utilization of materials in the direct sulfonation of
phthalocyanine. The optimal reaction conditions were using a phthalic anhydride mixture with a sulfonation
degree of 60% as the raw material, a ratio of urea to PA–SPA mixture of 4:1, a ratio of cobalt chloride to
PA–SPA mixture of 1 : 4, ammonium molybdate (1 wt%) as catalyst, and carrying out the reaction at 260 1C for
Received (in Porto Alegre, Brazil)
th September 2013,
6
Accepted 31st October 2013
3
hours. Under these optimal conditions, a yield of 52.9% can be achieved. Through sweetening
experimental studies, the synthesized sulfonated cobalt(II) phthalocyanine had better sweetening performance
than the industrial catalysts, in both the liquid–liquid sweetening and fixed bed sweetening experiments.
A sweetening rate of 93% can be achieved in 20 min with the synthesized catalyst in a fixed bed.
DOI: 10.1039/c3nj01063e
www.rsc.org/njc
1
. Introduction
Metal phthalocyanines are widely used in organic thin film
1
–3
transistor (OTFT) gas sensors,
solar cell photosensitized
4–9
10–13
dyes, and photodynamic therapy,
because of their excellent
optical and electrical properties and their good thermal and
chemical stability. However, the solubility and aggregation problem
of phthalocyanine derivatives have a strong influence on the
14
processing and bioavailability, which greatly limits their applica-
tion. The introduction of a sulfonic group into phthalocyanine
derivatives to form sulfonated cobalt(II) phthalocyanine (CoSPc) can
Fig. 1 Synthetic route of sulfonated phthalocyanine via sulfonated phtha-
15–17
greatly improve the solubility.
Furthermore, CoSPc has been lic anhydride mixture.
widely used as a light oil sweetening catalyst, due to its excellent
18
performance for the catalytic oxidation of mercaptans.
In general, CoSPc is synthesized by two steps, which include number of sulfonic groups on the phthalocyanine ring and the
synthesizing the cobalt phthalocyanine first, then sulfonating it performance of the phthalocyanine metal can be well controlled
with fuming sulfuric acid. Compared with this two-step proce- during the reaction. Therefore, studying the solid-phase synthesis
dure, the direct one-step solid-phase synthesis of CoSPc from and catalytic sweetening performance of CoSPc from SPA is very
sulfonated phthalic anhydride (SPA) undoubtedly proved to be significant.
a promising route (as shown in Fig. 1). Sulfonation of phthalic
anhydride (PA) is not only more economical than sulfonation of
cobalt phthalocyanine, but also can avoid the loss of cobalt
phthalocyanine during the sulfonation process. Furthermore,
2
. Experimental
Materials and methods
by taking SPA as a starting material to synthesize the CoSPc, the Industrial 1 Catalyst (Shunfeng Company, Dongying) and
Industrial 2 Catalyst (Beijing Sanju New Material Co., Ltd., Beijing)
were used to compare the performance in catalytic sweetening.
State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering,
The reversed-phase high-performance liquid chromatography
system (RP-HPLC) consisted of a Waters 2695 Separations
China University of Petroleum, Qingdao 266580, China. E-mail: xiadh@upc.edu.cn;
Fax: +86 53286981565; Tel: +86 53286981869
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 663--668 | 663

View Article Online
Paper
NJC
À1
Module, a Waters 2996 Photodiode Array Detector and a C18 of 160 mg g ) was taken in a 150 mL flask (with magnetic
À1
À1
column (Venus-C18-5-100). A 42 : 58 (v/v) methanol–ammonium stirring at 1200 r min ). 10 mL of about 10 mg g CoSPc
À1
dihydrogen phosphate mixture (0.15 mol L ) was used as the in 10% NaOH solution was added. After 3, 5, 7, 9, 15, 20 and
mobile phase in the chromatography experiments. Chromato- 25 min, 2 mL of the solution was taken out and the sulfur
À1
graphic testing was carried out under a flow rate of 0.6 mL min
,
content of mercaptan was measured by potentiometric titration,
with a detection wavelength of 240 nm, a column temperature of and the removal rate of mercaptan was calculated.
0 1C and an injection volume of 20 mL. Infrared Spectroscopy In the fixed bed sweetening experiments, the CoSPc catalyst
IR) was analyzed by a Nicolet 6700 FTIR (Thermo Scientific). supported on activated carbon was prepared according to the
3
(
1
9
The NMR spectra were collected on a Varian Mercury UX300 literature. The procedure was the same as for liquid–liquid
spectrometer operating at 300 MHz in DMSO-d
spectroscopy was performed on a UV-2450 SHIMADZU UV-visible 10 mg g CoSPc in 10% NaOH solution.
spectrophotometer. Mass spectrometry was performed using a
6
. UV-visible sweetening, but 2 g of immobilized catalyst was used instead of
À1
Bruker Biflex III matrix assisted laser desorption–ionization time
of flight (MALDI-TOF) mass spectrometer equipped with a 337 nm
nitrogen laser. Both the 4-hydroxy-a-cyanocinnamic acid matrix 3.1 Sulfonation of PA
3
. Results and discussion
and the sample were dissolved in 1 : 1 (v/v) acetonitrile : water with
By studying the sulfonation of PA, the most suitable reaction
conditions for sulfonation are a SO to PA ratio of 1 : 3, a reaction
temperature of 140 1C and a reaction time of 2.5 hours, and under
1% trifluoroacetic acid, and 0.5 mL of this mixture solution was
3
placed on a metal sample plate and air-dried at ambient tempera-
ture. Mass spectra were acquired in positive linear mode and using
an acceleration voltage of 19 kV. All the reagents and solvents were
of analytical grade.
these conditions a PA–SPA mixture with a 60% sulfonation degree
1
can be obtained. H-NMR (DMSO-D
6
) of the SPA showed the
following: d: 12.90 (s), 7.872 (d, J = 1.507 Hz, 1H), 7.798 (dd, J =
8.289 Hz, J = 1.507 Hz, 1H), 7.661 (d, J = 8.289 Hz, 1H), 2.5 (s).
General procedure for sulfonation of PA
PA was added to a round bottom flask (RBF) with three-necks, then
a condenser and a thermometer were installed. The end of the
condenser was connected to the absorption bottle. The flask of
3
.2 Optimization of the phthalocyanine synthesis conditions
(1) Effect of SPA content on the synthesis of CoSPc. Urea and
the PA–SPA mixture were mixed in a ratio of 5 : 1, and the CoSPc
was synthesized at 180 1C for 2 h. From Fig. 2, it can be seen that
as the proportion of SPA in the PA–SPA mixture increases, the
sulfur content of the CoSPc also increases, while the yield is
changed little. Therefore, in order to obtain a higher sulfonation
degree of CoSPc, a PA–SPA mixture with a SPA proportion of 60%
was directly used in the following synthesis of CoSPc.
fuming sulfuric acid was heated at 120 1C. The SO released went
3
into the RBF though the glass tube and contacted with the PA. The
sulfonation reaction was carried out at a certain temperature. After
the reaction, the rest of the fuming sulfuric acid was weighed, and
the reduced quantity of fuming sulfuric acid was approximately
3
equal to the amount of SO that reacted with the PA.
Determination of the degree of sulfonation of the sulfonation
product
(2) Effect of the molar ratio of urea to PA–SPA mixture on
the synthesis of CoSPc. Urea and PA–SPA mixture were mixed in
ratios of 2 : 1, 3 : 1, 4 : 1, 5 : 1, 6 : 1 and 7 : 1, and CoSPc was
synthesized at 180 1C for 2 h. From the sulfur content and yield
After sulfonation, a small amount of the sulfonation product
was taken for analysis by RP-HPLC. The concentration of PA
and SPA were calculated from the peak area by the external
standard method. The sulfonation degree was the proportion of
PA in the PA–SPA mixture.
Solid-phase synthesis of CoSPc
About 1 g of the mixture of PA and SPA (PA–SPA mixture), and
certain proportions of urea, cobalt chloride (the molar ratio of
cobalt chloride to PA–SPA mixture was 1 : 4) and ammonium
4 2 4
molybdate ((NH ) MoO , 1 wt% relative to the PA–SPA mixture)
were weighed, mixed well in a crucible and heated in a muffle
furnace. After a predetermined period of time, the mixture was
taken out, cooled, and then extracted for 10 h with acetone in a
Soxhlet extractor. Finally the CoSPc mixture was obtained as a
deep blue powder after drying for 10 h in a vacuum drying oven.
Procedures for experimental sweetening
In liquid–liquid sweetening, about 50 mL of a solution of
n-hexanethiol in petroleum ether with a sulfur content
of 200 mg g (or a gasoline with a mercaptan sulfur content and sulfur content of CoSPc.
Fig. 2 The effect of sulfonated phthalic anhydride content on the yield
À1
664 | New J. Chem., 2014, 38, 663--668
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
NJC
Paper
Fig. 3 The effect of the molar ratio of urea to PA–SPA mixture on the
Fig. 5 Effect of reaction time on the yield and sulfur content of CoSPc.
yield and sulfur content of CoSPc.
(shown in Fig. 3), it can be seen that, in the CoSPc synthesis fast, and there will be surplus of the reactant leading to
process, as the amount of urea increased, the yield increased, reduction of the yield. When the temperature reached 340 1C,
reaching a maximum at 4 : 1, then slowly decreased. Except the sulfur content and yield of the resulting product became very
for the maximum being reached at 5 : 1, the trend for sulfur low, as there may be more loss of reactant and sulfonic acid
content was similar to that of the yield. Therefore, in order to groups. Through experimental studies, the best CoSPc synthesis
maximize the yield, the optimum CoSPc synthesis ratio of urea reaction temperature should be 260 1C.
to PA–SPA mixture is 4 : 1.
(4) Effect of reaction time on the synthesis of CoSPc. Six
(
3) Effect of temperature on the synthesis of CoSPc. Six sets sets of raw materials (urea and PA with a ratio of 4 : 1) were
of raw materials (the molar ratio of urea to PA–SPA mixture was reacted at 260 1C, for 0.5, 1, 2, 3, 4 and 5 h, respectively. As can
fixed at 4 : 1) were reacted, respectively, at 140 1C, 180 1C, 220 1C, be seen from Fig. 5, the yield and the sulfur content showed similar
260 1C, 300 1C and 340 1C, for 2 h. As can be seen from Fig. 4, as trends with reaction time, and that is they both increased first and
the temperature rises, the reaction yield and the sulfur content then decreased. The yield and sulfur content reached a maximum
increased first, then the maximum values were obtained at at 3 h, and then slowly declined. This showed that the reaction was
260 1C, then they decreased. When the temperature was lower substantially complete after 3 h. Extension of the reaction time may
than 260 1C, the reaction is relatively slow. The reaction rate is lead to the decomposition rate of the products being greater than
accelerated with temperature increase. When more than 260 1C, the rate of generation. This study showed that 3 h is the most
the temperature is too high, the decomposition and loss of urea appropriate reaction time for the synthesis of CoSPc.
may be too fast, or phthalic anhydride sublimation may be too
After optimization, the optimum synthesis conditions for CoSPc
were as follows: 60% PA–SPA mixture as the reaction raw material,
a ratio of urea to PA–SPA mixture of 4 : 1, and the reaction being
carried out at 260 1C for 3 hours. Under these conditions, a yield of
52.9% and a sulfur content of 3.52% can be obtained.
3
.3 Characterization of CoSPc
1) Elemental analysis and mass spectrometry. By elemental
analysis and calculation for CoSPc (C H CoN O S): C, 58.99;
(
3
2
16
8 3
H, 2.48; N, 17.20. Found: C, 61.79; H, 2.58; N, 18.20. In mass
+
spectrometry (MALDI-TOF-MS), peak at 652.2 (M + H) ,
calcd for mono-substituted CoSPc (C32
H
16CoN
peak at 732.1 (M + H) , calcd for disubstituted CoSPc
16CoN ): 731.00. The mass of the CoSPc with one or
8 3
O S): 651.04;
+
(C
32
H
8 6 2
O S
two sulfonic acid groups can be found. The mass peak of CoPc
is not found, which may be due to its poor solubility in aceto-
nitrile and water. This shows that the product obtained was a
mixture, which mixed with different degrees of sulfonated
cobalt phthalocyanine. This is also verified by elemental analysis.
This mixture is difficult for further purification and characterization,
Fig. 4 Effect of temperature on the yield and sulfur content of CoSPc.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 663--668 | 665

View Article Online
Paper
NJC
Fig. 7 IR spectra of CoPc and the three CoSPc catalysts (from top to
bottom: CoPc, Industrial 1, synthesized, Industrial 2).
(3) IR spectra of CoSPc. The IR spectra of CoPc and the
CoSPcs (synthesized, Industrial 1 and Industrial 2) are shown in
Fig. 7. By comparing the spectra and references, it can be
À1
analyzed that the peaks at 3400 cm are the –NH stretching
À1
of the amide, and the peaks at 3200 cm are the association
absorption peaks of the hydroxyl from the sulfonic acid group
À1
in the spectrum of CoSPc. The peaks at about 3100 cm are the
stretching vibration of the C–H on the aromatic ring, the peaks
À1
at about 1650 cm are the CQC stretching vibration on the
À1
aromatic ring, and the peak at 1400 cm is the CQN stretch-
Fig. 6 (a) The UV spectra of the three CoSPc catalysts in DMF (about ing vibration. The existence of this series of peaks shows the
À1
1
(
.0 mg L ), from top to bottom: Industrial 1, Industrial 2, synthesized.
À1
presence of the phthalocyanine ring. The peaks at 1100 cm
b) A local enlargement of (a), from left to right: Industrial 1, Industrial 2,
are characteristic absorption peaks of the SQO symmetric and
synthesized.
asymmetric stretching vibrations of the sulfonic acid groups,
À1
20
and the peaks at 619 cm are the C–S stretching vibrations.
but this has little effect on industrial gasoline sweetening These two sets of peaks show that the sulfonic acid group
applications.
2
1
substituted the hydrogen on the aromatic ring.
(
2) UV spectra of CoSPc. The UV spectra of the three CoSPc
catalysts (synthesized, Industrial 1 and Industrial 2) are almost
consistent (see Fig. 6). Relative to cobalt phthalocyanine, the
order of red shift and peak width of the CoSPcs is synthesized >
Industrial 2 > Industrial 1, which is the same order as for the
sulfur content (as shown in Table 1). This may be because of
differences in the isomer structures, aggregation behavior and
sulfur contents. If the sulfur content is higher, there is a greater
proportion of CoSPc in the mixture, and thus the greater the
degree of conjugation and aggregation.
Table 1 Comparison of the maximum absorption wavelengths and sulfur
contents of the three CoSPc catalysts
Industrial 1
Industrial 2
Synthesized
l
l
max, Q-band/nm
max, B-band/nm
660
327
1.58
0.32
662
329
2.24
0.46
664
332
3.52
0.72
Sulfur content/%
Average number of
sulfonic acid group
Fig. 8 Comparison of the n-hexanethiol removal performance of the
three CoSPcs in petroleum ether.
666 | New J. Chem., 2014, 38, 663--668
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014

View Article Online
NJC
Paper
the synthesized CoSPc (as shown in Fig. 9). The catalyst sweet-
ening effect of the synthesized CoSPc is more obvious for the
large molecular weight mercaptan in gasoline compared with
the industrial CoSPcs.
(2) Fixed bed sweetening. Fig. 10 shows the evaluation of
the fixed bed catalytic sweetening capability for n-hexanethiol.
A sweetening rate of 93% can be achieved in 20 min with the
synthesized catalyst. By comparison of the removal perfor-
mance of the CoSPcs on a fixed bed, the sweetening perfor-
mance of the synthesized CoSPc was significantly better than
the two kinds of industrial CoSPc. Moreover this order followed
with the liquid–liquid sweetening experiments.
4. Conclusions
Fig. 9 Comparison of the mercaptan removal performance of the three The optimum synthesis conditions of CoSPc are as follows:
kinds of CoSPc in gasoline.
using phthalic anhydride mixture with a sulfonation degree of
60% as the raw material, a ratio of urea to PA–SPA mixture
of 4 : 1, a ratio of cobalt chloride to PA–SPA mixture of 1 : 4,
and carrying out the reaction at 260 1C for 3 hours. Under
these optimal conditions, a yield of 52.9% can be achieved. The
UV-visible spectroscopy and infrared spectroscopy results can
verify the presence of the structure of CoSPc. The liquid–liquid
and fixed bed sweetening experiments show that the catalyst
obtained from one step solid-phase synthesis has better perfor-
mance than the industrial catalysts.
3
.4 Comparison of the sweetening performance of
synthesized CoSPc and industrial CoSPc
1) Liquid–liquid sweetening. Comparison of the sweetening
(
ability of the three CoSPc catalysts (synthesized, Industrial 1,
Industrial 2) in petroleum ether (Fig. 8) or in gasoline (Fig. 9)
shows that the synthesized CoSPc demonstrated the best catalytic
performance of the three CoSPcs in a very short period of time.
The synthesized CoSPc achieved the biggest conversion rate
(90%) at 20 min, followed by the Industrial 2 CoSPc. This order
is consistent with the sulfur content of the three catalysts, which
is the same as the order of the number of sulfonic groups in the
Acknowledgements
CoSPcs. This shows that the catalytic sweetening performance is This work is supported by the Postdoctoral Science Foundation
directly related to the number of sulfonic acid groups.
of China (2012M521386).
There is a relatively large molecular weight mercaptan in
gasoline, so it is not easy to be removed. Therefore, the two
industrial CoSPcs can only remove 60% of the mercaptan in Notes and references
20 min, but about 90% of this mercaptan can be removed by
1
J. Hong Park, J. Edward Royer, E. Chagarov, T. Kaufman-
Osborn, M. Edmonds, T. Kent, S. Lee, W. C. Trogler and
A. C. Kummel, J. Am. Chem. Soc., 2013, 135(39),
1
4600–14609.
E. van Faassen and H. Kerp, Sens. Actuators, B, 2003, 88(3),
29–333.
F. I. Bohrer, C. N. Colesniuc, J. Park, M. E. Ruidiaz,
I. K. Schuller, A. C. Kummel and W. C. Trogler, J. Am. Chem.
Soc., 2009, 131, 478–485.
2
3
3
4
K. Vasseur, K. Broch, A. L. Ayzner, B. P. Rand, D. Cheyns,
C. Frank, F. Schreiber, M. F. Toney, L. Froyen and
P. Heremans, ACS Appl. Mater. Interfaces, 2013, 5(17),
8505–8515.
5
6
7
M. Zhang, C. Shao, Z. Guo, Z. Zhang, J. Mu, P. Zhang, T. Cao
and Y. Liu, ACS Appl. Mater. Interfaces, 2011, 3(7), 2573–2578.
N. Y. Borovkov and S. V. Blokhina, J. Phys. Chem. C, 2011,
115(36), 17945–17951.
B. C. O’Regan, I. L ´o pez-Duarte, M. Victoria Mart ´ı nez-D ´ı az,
A. Forneli, J. Albero, A. Morandeira, E. Palomares, T. Torres
and J. R. Durrant, J. Am. Chem. Soc., 2008, 130(10), 2906–2907.
Fig. 10 Comparison of the n-hexanethiol removal performance of the
three CoSPcs on a fixed bed.
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014
New J. Chem., 2014, 38, 663--668 | 667

View Article Online
Paper
NJC
8
9
M. Eleni Ragoussi, J. Jos ´e Cid, J. Ho Yum, G. de la Torre, 15 K. Ogawa, S. Kinoshita, H. Yonehara, H. Nakahara and
D. Di Censo, M. Gr ¨a tzel, M. K. Nazeeruddin and T. Torres,
K. Fukuda, J. Chem. Soc., Chem. Commun., 1989,
Angew. Chem., Int. Ed., 2012, 51(18), 4375–4378.
477–479.
M. J. Jurow, B. A. Hageman, E. DiMasi, C. Y. Nam, C. Pabon, 16 R. W. Boyle and J. E. van Lier, Synlett, 1993,
C. T. Black and C. Michael Drain, J. Mater. Chem. A, 2013, 1,
557–1565.
0 X. Jia, F. Feng Yang, J. Li, J. Yong Liu and J. Ping Xue, J. Med.
351–352.
1
17 W. M. Sharman, S. V. Kudrevich and J. E. van Lier, Tetra-
hedron Lett., 1996, 37, 5831–5834.
1
1
1
1
1
Chem., 2013, 56(14), 5797–5805.
18 Y. S. Zhang, Master Degree Thesis, China University of
Petroleum, Shandong, 2007, pp. 2–15.
19 G. G. Lu, Y. L. Zhou, Y. Z. Xiang and D. H. Xia, J. Porphyr.
Phthalocya., 2010, 14(10), 904–910.
20 M. S. Robert, X. W. Francis and J. K. David, Spectrometric
Identification of Organic Compounds [M], John Wiley & Sons,
2006, pp. 102–104.
1 A. Jarota, M. Tondusson, G. Galle, E. Freysz and
H. Abramczyk, J. Phys. Chem. A, 2012, 116, 4000–4009.
2 B. Bro ˙z ek Płuska, A. Jarota, K. Kurczewski and
H. Abramczyk, J. Mol. Struct., 2009, 924–926, 338–346.
3 H. Abramczyk, B. Brozek-Pluska, M. Tondusson and
E. Freysz, J. Phys. Chem. C, 2013, 117, 4999–5013.
4 M. P. D. Filippis, D. Dei, L. Fantetti and G. Roncucci, 21 Y. R. Peng, N. S. Chen and J. L. Huang, Chin. J. Appl. Chem.,
Tetrahedron Lett., 2000, 41, 9143–9147.
2002, 19(8), 730–733.
668 | New J. Chem., 2014, 38, 663--668
This journal is ©The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2014