Selective oxidation of sulfurs and oxidation desulfurization of model oil by 12-tungstophosphoric acid on cobalt-ferrite nanoparticles as magnetically recoverable catalyst

Article abstract of DOI:10.1016/S1872-2067(15)60862-2

Silica-coated CoFe₂O₄ nanoparticles were prepared and used as a support for the immobilization of 12-tungstophosphoric acid, to produce a new magnetically separable catalyst. This catalyst was characterized using X-ray diffraction, wavelength-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, laser particle size analysis, and vibrating sample magnetometry. The catalyst showed high activity in the selective oxidation of thioethers and thiophenes to the corresponding sulfones under mild conditions. The catalytic activity of the nanocatalyst in the oxidative desulfurization of model oil was investigated. The effect of nitrogen-containing compounds on sulfur removal from the model oil was also evaluated. The catalyst showed high activity in the oxidative desulfurization of diesel. The catalyst can be readily isolated from the oxidation system using an external magnet and no obvious loss of activity was observed when the catalyst was reused in four consecutive runs.

Full text of DOI:10.1016/S1872-2067(15)60862-2

Chinese Journal of Catalysis 36 (2015) 1342–1349
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
Article
Selective oxidation of sulfurs and oxidation desulfurization of model
oil by 12-tungstophosphoric acid on cobalt-ferrite nanoparticles as
magnetically recoverable catalyst
Ezzat Rafiee a,b,*, Nasibeh Rahpeyma a
a Faculty of Chemistry, Razi University, Kermanshah 67149, Iran
b Institute of Nano Science and Nano Technology, Razi University, Kermanshah 67149, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
Silica-coated CoFe2O4 nanoparticles were prepared and used as a support for the immobilization of
12-tungstophosphoric acid, to produce a new magnetically separable catalyst. This catalyst was
characterized using X-ray diffraction, wavelength-dispersive X-ray spectroscopy, Fourier-transform
infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, laser par-
ticle size analysis, and vibrating sample magnetometry. The catalyst showed high activity in the
selective oxidation of thioethers and thiophenes to the corresponding sulfones under mild condi-
tions. The catalytic activity of the nanocatalyst in the oxidative desulfurization of model oil was
investigated. The effect of nitrogen-containing compounds on sulfur removal from the model oil was
also evaluated. The catalyst showed high activity in the oxidative desulfurization of diesel. The cata-
lyst can be readily isolated from the oxidation system using an external magnet and no obvious loss
of activity was observed when the catalyst was reused in four consecutive runs.
Received 20 February 2015
Accepted 7 April 2015
Published 20 August 2015
Keywords:
Phosphotungstic acid
Cobalt
Ferrite
Oxidative desulfurization
Dibenzothiophene
Magnetic catalyst
© 2015, Dalian Institute of Chemical Physics, Chinese Academy of Sciences.
Published by Elsevier B.V. All rights reserved.
1. Introduction
from fuels and industrial effluents, to satisfy new environmen-
tal legislation [2–5].
Among recent developments in catalysis, "clean oxidation
catalysis", involving catalysis and H2O2, is receiving much at-
tention because of the importance of oxidation reactions in the
manufacture of fine chemicals. These catalytic systems pro-
mote the oxidation of organic substrates because of their oxy-
gen content, and are low cost, safe to store and use, and, im-
portantly, the use of H2O2 is environmentally friendly. These
advantages have encouraged the development of practical
procedures for the selective oxidation of organic sulfur com-
pounds, not only because of the extensive use of sulfoxides and
sulfones as synthetic intermediates in the pharmaceutical in-
dustry [1], but also because the oxidative desulfurization (ODS)
process is an effective method for removing sulfur compounds
ODS is an alternative or complementary technology to hy-
drodesulfurization for deep desulfurization [6]. It has several
advantages such as mild reaction conditions (ambient pressure
and low temperature), high selectivity, and the potential for
desulfurization of sterically hindered sulfur compounds such as
dibenzothiophene (DBT) [7]. In the ODS process, aromatic sul-
fur compounds such as benzothiophene (BT), DBT, and their
alkylated derivatives are oxidized to the corresponding sulfone
or sulfoxide; these are highly polar and can be removed using
organic extractants [8–14].
Various catalytic systems have been reported for ODS
[15–22]. Among these, polyoxometalates (POMs) have higher
sulfur removal efficiencies because of their unusual properties.
* Corresponding author. Tel/Fax: +98-83-34274559; E-mail: ezzat_rafiee@yahoo.com
DOI: 10.1016/S1872-2067(15)60862-2 | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 36, No. 8, August 2015

Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
1343
The main obstacle to industrial applications of homogeneous
POMs is that they are difficult to recover from the reaction me-
dium. These materials are therefore usually impregnated on
suitable materials [23–29].
by sonication. The mixture was stirred to obtain CoFe@Si-PW
magnetic nanoparticles. The catalyst was collected using a
permanent magnet and dried under vacuum overnight.
Recently, progress has been achieved using amphiphilic
POM catalysts, which are synthesized from a combination of
quaternary ammonium cations and POM anions. These com-
pounds can form emulsion droplets, which act as homogeneous
catalysts at the interface of two immiscible liquids, giving high
activities during oxidative processes [30–32].
We synthesized and characterized a novel, more effective,
magnetically separable catalyst by the immobilization of
12-tungstophosphoric acid (PW) on the surfaces of sili-
ca-coated CoFe2O4 magnetic nanoparticles (CoFe@Si). This
catalyst (denoted by CoFe@Si-PW) was characterized using
various techniques. Selective oxidation of sulfur compounds
and desulfurization of model oil were investigated using an
H2O2/CoFe@Si-PW catalytic system. The effects of reaction
temperature, catalyst loading, and oxidant to sulfur (O/S) mo-
lar ratio were studied to optimize the reaction conditions. The
ODS of model oil was investigated under the optimized reaction
conditions. The effect of nitrogen-containing compounds on
ODS were investigated by adding quinoline and indole to the
oxidation system.
2.2. Catalyst characterization
Fourier-transform infrared (FT-IR) spectroscopy was per-
formed on KBr pellets using an FTIR-spectrometer (Alpha).
X-ray diffraction (XRD) was performed using a D8 ADVANCE
diffractometer (Bruker-AXS, Germany). The magnetic proper-
ties of CoFe@SiO2-PW were determined using a BHV-55 (Riken,
Japan) vibrating sample magnetometer (VSM). The morphology
of the supported catalyst was examined using scanning elec-
tron microscopy (SEM; XL30, Philips). Transmission electron
microscopy (TEM) was performed using a Zeiss EM900 trans-
mission electron microscope with an accelerating voltage of 80
kV. The size distributions and zeta potentials of the samples
were determined using
a laser particle size analyzer
(HPPS5001, Malvern, UK). The total S contents of the model oils
were determined using an elemental analyzer (Analytik Jena
AG-multi EA® 3100). The W content of the catalyst was deter-
mined using inductively coupled plasma atomic emission spec-
troscopy (ICP-AES; Spectro Ciros CCD spectrometer).
2.3. Catalytic tests
2. Experimental
2.3.1. Oxidation of liquid sulfides
2.1. Catalyst preparation
Liquid sulfides were oxidized to the corresponding sulfones
by stirring a solution of the sulfide (1 mmol) and the catalyst
(0.04 g) in n-heptane (4 mL). A certain amount of H2O2 (30%
aq.) was added as the oxidant. The mixture was stirred for a
specified time at room temperature. After completion of the
reaction, the catalyst was separated from the reaction mixture
using an external magnet. The corresponding sulfone products
were extracted from the reaction mixture with Et2O. The sol-
vent was evaporated to generate the crude product. The crude
product was purified by column chromatography on silica gel
using hexane/ethyl acetate as the eluent (method a).
All materials were commercial reagent grade and obtained
from Merck, Aldrich, and Fluka, and used without further
purification.
The CoFe@Si-PW catalyst was synthesized according to the
procedure shown in Scheme 1. The CoFe2O4 nanoparticles were
prepared using a coprecipitation method. CoCl2·6H2O (25 mL,
0.1 mol/L) and FeCl3·6H2O (25 mL, 0.2 mol/L) were dissolved
in distilled water and kept at 70 °C. NaOH solution (24 mL, 3.0
mol/L) was added to the salt solution. The dark brown product
was washed several times with distilled water and redispersed
in distilled water to give a stable brown magnetic dispersion.
CoFe2O4 nanoparticles (0.04 g) were dispersed in ethanol (160
mL). This dispersion was homogenized ultrasonically in a wa-
ter bath for 10 min. Finally, water (40 mL), tetraethylorthosili-
cate (1 mL), and ammonia solution (5 mL) were slowly added
to this dispersion. The obtained CoFe@Si nanoparticles were
separated using a permanent magnet, washed with distilled
water, and dried under vacuum. The synthesis of 40 wt% PW
on CoFe@Si was performed by dissolving PW (0.5 g) in dry
methanol (5 mL). This solution was added drop-wise to a sus-
pension of CoFe@Si (1.0 g in 50 mL methanol) with dispersion
2.3.2. Oxidation of solid sulfides
Solid sulfides were oxidized to the corresponding sulfones
by stirring a solution of the sulfide (1 mmol) and the catalyst
(0.15 g) in n-heptane-ethanol (v/v, 4:2). Then a certain amount
of H2O2 (30% aq.) was added as the oxidant. The mixture was
stirred for a specified time at 60 °C, and the reaction was mon-
itored using thin-layer chromatography. After completion of
the reaction, the catalyst was separated from the reaction solu-
tion using an external magnet. The corresponding sulfone
products were separated from the reaction mixture. The sol-
vent was evaporated to generate the crude product. The crude
2 Fe3+
+
Co2+
Co-precipitation
NaOH
TEOS
Immobilization
CoFe@Si-PW
PW
CoFe@Si
Scheme 1. Schematic diagram of preparation of CoFe@Si-PW catalyst.

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Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
Table 1
Compositions of model oils used in this study (ppm).
(3)
(2)
Model oil
Feed 1
Feed 2
Feed 3
Feed 4
DBT
500
100
500
500
BT
250
—
250
250
Thiophene
250
Indole
—
—
60
—
Quinolin
—
—
—
60
—
250
250
DBT: dibenzothiophene. BT: benzothiophene.
product was purified by column chromatography on silica gel
using hexane/ethyl acetate as the eluent (method b).
(1)
2.3.3. Catalytic ODS of model oil
4000 3600 3200 2800 2400 2000 1600 1200 800 400
Wavenumber (cm1)
Model oils were prepared by dissolving various amounts of
S and N compounds in n-heptane. The compositions of the
model oils are shown in Table 1. The oxidation reaction was
investigated using the model oil (5 mL, feeds 1–3) and catalyst
in ethanol (1 mL) as an extracting solvent. A certain amount of
H2O2 (30% aq.) was added to the mixture. The mixture was
stirred at 60 °C for 4 h. The catalyst was separated from the
reaction mixture using an external magnet. The S content of the
model oil was determined using an elemental analyzer.
Fig. 1. FT-IR spectra of CoFe2O4 (1), CoFe@Si (2), and CoFe@Si-PW (3).
CoFe@Si-PW
2.3.4. Effect of nitrogen compounds on ODS of model oil
The effect of nitrogen compounds on the ODS of model oil
was investigated by combining the model oil (5 mL, feeds 3 and
4) and catalyst with H2O2 (O/S: 12) and ethanol (1 mL). The
mixture was stirred at 60 °C for 4 h. The catalyst was separated
from the reaction mixture using an external magnet. The S
content of the model oil was determined using an elemental
analyzer.
PW
CoFe@Si
10
20
30
40
2/(o )
Fig. 2. XRD patterns of CoFe@Si, PW, and CoFe@Si-PW.
50
60
70
3. Results and discussion
FT-IR spectrum of the CoFe@Si-PW particles has peaks at 890
and 981 cm−1, which are attributed to the W–O–W and W=O
stretching modes, respectively, of PW [36,37]. The band at
1079 cm−1 corresponds to the P–O stretching mode of PW.
The XRD patterns of CoFe@Si, CoFe@Si-PW, and PW are
shown in Fig. 2. There are no peaks from crystalline SiO2, be-
cause it remains amorphous because of the low-temperature
synthetic method used. When PW is immobilized on the sur-
faces of the CoFe@Si magnetic particles, the characteristic
peaks of PW are observed for CoFe@Si-PW, which implies re-
tention of the crystalline character of PW [38].
3.1. Catalyst characterization
The FT-IR spectra of CoFe2O4, CoFe@Si, and CoFe@Si-PW
are shown in Fig. 1. All samples show two intense and broad
peaks at around 3395 and 1622 cm−1, associated with the
stretching vibrations of free or adsorbed water remaining in
the sample. The presence of Co–O and Fe–O bonds in CoFe2O4 is
confirmed by the peak at 579 cm−1, which shifts to 596 cm−1
after coating with silica [33]. The bands at 1087 cm−1, along
with the shoulder at 1200 cm−1, correspond to the stretching
mode of the Si–O–Si bond in silica, and the band at 464 cm−1 is
assigned to Si–O–Si or O–Si–O bending modes [34,35]. The
The morphology of the CoFe@Si-PW catalyst was examined
using SEM (Fig. 3(a)). It shows that the obtained particles are
(b)
(a)
Fig. 3. SEM image of CoFe@Si-PW (a) and elemental maps of Fe, Co, Si, and W atoms in CoFe@Si-PW (b).

Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
1345
80
70
60
50
40
30
20
10
0
0.1
1
10
100
1000
10000
Size (nm)
Fig. 4. TEM image of CoFe@Si-PW.
Fig. 5. Particle size distribution of CoFe@Si-PW determined by a laser
particle size analyzer.
agglomerated as a consequence of strong magnetization and
the high particle surface energy. Wavelength-dispersive X-ray
(WDX) images, which mapped Fe, Si, Co, and W elements indi-
vidually in a cross-section, are shown in Fig. 3(b). The WDX
analysis shows excellent uniform distribution of PW on
CoFe@Si magnetic nanoparticles.
1.5
1.0
0.5
The TEM images indicate that the CoFe@Si-PW nanoparti-
cles are almost spherical (Fig. 4). The size distribution of the
CoFe@Si-PW catalyst particles was measured using a laser
particle size analyzer. The results (Fig. 5) show particles of
mean diameter 137 nm with a narrow size distribution. This
mean diameter is lower than that determined using laser parti-
cle size analysis. This is mainly because of the different sample
preparation processes. TEM gives the size in the dry state,
whereas laser particle size analysis gives the size of the hy-
drated sample.
0.0
-0.5
-1.0
-1.5
-10000
-6000
-2000
Applied field (Oe)
Fig. 6. Magnetic hysteresis loops of CoFe@Si-PW.
2000
6000
10000
The magnetic properties of the catalyst were studied using a
VSM, with a peak field of 10 kOe. As shown in Fig. 6, the
CoFe@Si-PW catalyst was ferromagnetic. The Ms value was
lower than that reported for bulk samples [39]. This decrease
in the Ms is mainly attributed to the small particle surface effect,
which becomes more dominant as the particle size decreases
[40], and may arise from greater disorder of surface spins and
the presence of SiO2 (which forms a diamagnetic matrix, which
dilutes the magnetization of the otherwise compacted ferrite
particles).
of a model substrate, namely methyl phenyl sulfide (MPS),
were investigated (Fig. 7) to optimize the reaction conditions
for the liquid sulfides. The results show that increasing the
reaction temperature had no effect on the yield, but decreased
the reaction time (Fig. 7(a)). Subsequent experiments were
therefore performed at room temperature. As shown in Fig.
7(b), use of an 8:1 O/S molar ratio gave methyl phenyl sulfone
(MPSO2) as the sole product, in 98% yield. When the catalyst
loading was decreased from 0.04 to 0.02 g, the yield of MPSO2
decreased. Increasing the catalyst weight from 0.04 to 0.08 g
did not significantly increase the MPSO2 yield (Fig. 7(c)).
3.2. Catalytic reactions
The best result was therefore obtained using 0.04 g of cata-
lyst and an 8:1 O/S molar ratio at room temperature. These
The effects of various reaction parameters on the oxidation
100
(c)
(a)
(b)
80
60
40
20
0
R.T.
0.02 g
0.04 g
0.08 g
1:1
4:1
8:1
40 oC
70 oC
0
5
10
15
20
25
30 0
5
10
15
20
0
5
10
15
20
25
Time (min)
Time (min)
Time (min)
Fig. 7. Effects of temperature (O/S molar ratio 4:1, catalyst 0.04 g) (a), O/S molar ratio (catalyst 0.04 g, room temperature) (b), and amount of catalyst
(O/S molar ratio 8:1, room temperature) (c) on selective oxidation of MPS to MPSO2 in the presence of CoFe@Si-PW.

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Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
optimized reaction conditions were used to oxidize a series of
liquid sulfides to their corresponding sulfones (Table 2, entries
1–7). The results in Table 2 show that aromatic and aliphatic
sulfones were mostly obtained with 100% selectivity.
Table 2
Oxidation of sulfides to sulfones with H2O2 using CoFe@Si-PW as cata-
lyst.
Entry
1
Substrate
Time (min) Yield a (%)
Optimization of the conditions for oxidation of solid sulfur
compounds was performed using DBT as a model substrate. In
this study, ethanol was used as the cosolvent for extractive
desulfurization of the product, because it can be derived from
agricultural products, is renewable and biologically less harm-
ful in the environment, and has low toxicity compared with
other cosolvents. The oxidation of DBT did not proceed at room
temperature, therefore the influence of the O/S molar ratio
(Fig. 8) and catalyst loading (Fig. 9) on DBT oxidation was in-
vestigated at 60 °C. The results show that when 0.15 g of cata-
lyst and a 12:1 O/S molar ratio were used, the corresponding
sulfone (DBTO2) was produced with 100% selectivity.
Various solid substrates were oxidized to the corresponding
sulfones under these optimized conditions, with high selectivi-
ties (Table 2, entries 8–11). The reactivities of the sulfur com-
pounds were influenced by two main factors, i.e., the electron
density on the S atom and the steric hindrance of the sulfur
compound. The electron density on the S atom of thiophene
(entry 7) is lower than that on the BT sulfur (entry 9), therefore
its reactivity is lower. The reactivity of DBT was lower than that
of BT because of the higher steric hindrance.
S
15 b
98
Ph
S
2
30 b
94
Ph
S
3
4
5
6
7
75 b
10 b
81
96
96
95
83
Ph
Ph
S
S
S
10 b
10 b
S
180 b
S
8
9
240 c
130 c
80
98
S
10
11
45 c
60 c
91
8
Ph
Ph
S
Ph
Ph
S
a
Isolated yield; all products were identified by comparing their NMR
values with those in authentic samples [41–44].
b Method a. c Method b.
100
(b)
(c)
(a)
Sulfone
Sulfone
Sulfone
Sulfoxide
80
60
40
20
0
Sulfoxide
Sulfoxide
1
2
3
4
1
2
3
4
5
1
2
3
4
5
Time (h)
Time (h)
Time (h)
Fig. 8. Effect of O/S molar ratio in the selective oxidation of DBT to DBTO2 in the presence of CoFe@Si-PW (0.15 g) at 60 °C. (a) 8:1; (b) 12:1; (c) 14:1.
100
(c)
(a)
(b)
(d)
Sulfone
Sulfoxide
Sulfone
Sulfoxide
Sulfone
Sulfoxide
Sulfone
Sulfoxide
80
60
40
20
0
1
2
3
4
1
2
3
4
1
2
3
4
5
1
2
3
4
5
Time (h)
Time (h)
Time (h)
Time (h)
Fig. 9. Effect of the catalyst amount in selective oxidation of DBT to DBTO2 in the presence of CoFe@Si-PW at 60 °C and O/S = 12:1. (a) 0.02 g; (b) 0.03
g; (c) 0.04 g; (d) 0.05 g.

Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
1347
100
80
60
40
20
0
(b)
(a)
Model oil
Model oil + quinoline
Quinoline
Model oil
Model oil + indole
Indole
0
50
100
150
200
250
300 0
50
100
150
200
250
300
Time (min)
Time (min)
Fig. 10. Effect of nitrogen compounds indole (a) and quinoline (b) on ODS of model oil (feeds 3 and 4) at 60 °C (O/S = 12:1, catalyst 0.15 g).
The ODS of model oil containing various S compounds (feed
100
98
96
94
92
90
88
86
84
100
98
96
94
92
90
88
86
84
1) was performed using the optimized reaction conditions. The
S removal from the model oil reached 90% after 4 h. The
desulfurization efficiency of the catalyst was investigated using
ODS of the model oil with a low concentration of DBT (feed 2).
The results show that S removal from the model oil reached
85% after 4 h. This shows that the catalyst is efficient even at
low DBT concentrations.
Activity tests were carried out on the model oils containing
nitrogen compounds (feeds 3 and 4) to ascertain the effect of N
compounds on ODS. Fig. 10 shows the ODS conversions for the
model feeds containing indole and quinoline as a function of
reaction time. It shows that the ODS activity decreased more in
the presence of indole than in the presence of quinoline. These
results suggest that conversion of the nitrogen compounds
occurred before that of DBT, which implies that sulfur and ni-
trogen compounds are competitive in the oxidation. The higher
activity of indole compared with that of quinoline is ascribed to
the higher electron density on the nitrogen atom in indole [45].
Indole oxidation under mild reaction conditions has been re-
ported [46], but studies of quinoline oxidation have been per-
formed at high reaction temperatures (>200 °C) [47].
1
2
3
4
Run
Fig. 11. Reusability of CoFe@Si-PW and weight of recovered catalyst in
oxidation of MPS (method a).
The reusability of the catalyst was investigated for oxidation
of MPS. When the reaction was complete, the catalyst was sep-
arated from the mixture using a magnet, dried, and reused in a
second run with fresh substrates under the same reaction con-
ditions. The data shown in Fig. 11 indicate that the catalytic
oxidation ability of CoFe@Si-PW decreased slightly. After four
cycles, the yield of MPSO2 decreased by only 10%. This loss is
attributed to leaching of PW species from the solid. To test this
assertion, after the first cycle, the catalyst was separated, and
the reaction between MPS and H2O2 was carried out using the
clear solution. In this case, 5% of MPS was converted to the
sulfone, suggesting that leaching of PW species was negligible.
The weight percentages of PW in the fresh and recovered cata-
lysts after four runs, determined using ICP-AES, were 31.8 and
29.2 wt%, respectively. This means that 8.2 wt% of PW had
leached into the reaction media after four successive runs. The
weight of recovered catalyst after each run was also deter-
mined, and only 7.5 wt% of the catalyst was lost.
Scheme 2. Proposed ODS mechanism.
lized PW anions react with H2O2 to generate peroxytungstate
species [48,49]. This species facilitates transfer of the electro-
philic oxygen to the sulfide, to yield the corresponding sulfone.
The sulfone can be easily removed by extraction with a polar
solvent.
Table 3 compares the catalytic activity of the CoFe@Si-PW
catalyst with those of other reported catalysts for sulfoxidation
reactions. The CoFe@Si-PW catalyst shows higher activity than
the other catalysts and is magnetically recyclable.
4. Conclusions
PW-functionalized magnetic nanoparticles CoFe@Si-PW
were prepared by anchoring PW on the surfaces of sili-
The proposed mechanism is shown in Scheme 2. Immobi-

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Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
Table 3
Comparison of reaction data for the present method and other reported methods.
S content (ppm)
1000
400
500
1000
500
Catalyst
CoFe@Si-PW
W/D152
Reaction conditions
H2O2/60 °C/4 h
CYHPO/100 °C/40 min
H2O2/50 °C/6 h
Yield (%)
92
99
98
82.14
97.8
Ref.
This work
[50]
[51]
[52]
TBA4.2H0.8[PW11Zn(H2O)O39
Cu2(PcAN)2–WHZSM-5
PW12-MSPC
]
O2/60 °C/3 h
H2O2/60 °C/2 h
[53]
[13] Imtiaz A, Waqas A, Muhammad I. Chin J Catal, 2013, 34: 1839
[14] Zhu W S, Zhang J T, Li H M, Chao Y H, Jiang W, Yin S, Liu H. RSC Adv,
2012, 2: 658
[15] Lü H Y, Gao J B, Jiang Z X, Yang Y X, Song B, Li C. Chem Commun,
2007: 150
[16] Song H Y, Li G, Wang X S, Xu Y J. Catal Today, 2010, 149: 127
[17] Zhang M, Zhu W S, Xun S H, Li H M, Gu Q Q, Zhao Z, Wang Q. Chem
Eng J, 2013, 220: 328
[18] Ishihara A, Wang D H, Dumeignil F, Amano H, Qian E W H, Kabe T.
Appl Catal A, 2005, 279: 279
ca-coated CoFe2O4 magnetic nanoparticles. The nanoparticles
were successfully used in the oxidation of sulfur-containing
compounds. Various sulfides were selectively oxidized to their
corresponding sulfones under mild reaction conditions. The
CoFe@Si-PW catalyst also showed high activity for ODS of
model oils containing DBT, BT, and thiophene, using H2O2 as
the oxidant. The effect of nitrogen compounds on the ODS ac-
tivity of the catalyst was also studied. The results suggest that
quinoline inhibits ODS more than indole does. This is attributed
to competitive adsorption between sulfur and nitrogen com-
pounds for catalytic sites. This catalyst showed excellent cata-
lytic activity and high selectivity, and can be reused at least four
times, with only a slight decrease in catalytic activity.
[19] Zhang J, Wang A J, Wang Y J, Wang H Y, Gui J Z. Chem Eng J, 2014,
245: 65
[20] Zhu W S, Huang W L, Li H M, Zhang M, Jiang W, Chen G Y, Han C R.
Fuel Process Technol, 2011, 92: 1842
[21] Rafiee E, Eavani S. J Mol Catal A, 2013, 380: 18
[22] Rafiee E, Mirnezami F. J Mol Liq, 2014, 199: 156
[23] Yan X M, Lei J H, Liu D, Wu Y C, Guo L P. J Chin Chem Soc, 2007, 54:
911
[24] Kong L Y, Li G, Wang X S, Wu B. Energy Fuels, 2006, 20: 896
[25] Yazu K, Furuya T, Miki K. J Jpn Pet Inst, 2003, 46: 379
[26] Wang Y, Zhang J L, Wang X D, Ren J W, Zuo B J, Tang Y Q. Top Catal,
2005, 35: 35
[27] Xiong J, Zhu W S, Ding W J, Yang L, Chao Y H, Li H P, Zhu F X, Li H
M. Ind Eng Chem Res, 2014, 53: 19895
[28] Xiong J, Zhu W S, Ding W J, Yang L, Zhang M, Jiang W, Zhao Z, Li H
M. RSC Adv, 2015, 5: 16847
[29] Xiong J, Zhu W S, Li H M, Xu Y H, Jiang W, Xun S H, Liu H, Zhao Z.
AIChE J, 2013, 59: 4696
[30] Li C, Jiang Z X, Gao J B, Yang Y X, Wang S J, Tian F P, Sun F X, Sun X
P, Ying P L, Han C R. Chem Eur J, 2004, 10: 2277
[31] Lü H Y, Ren W Z, Wang H Y, Wang Y, Chen W, Suo Z H. Appl Catal A,
2013, 453: 376
[32] Lü H Y, Deng C L, Ren W Z, Yang X. Fuel Process Technol, 2014, 119:
87
[33] Ma M, Zhang Y, Yu W, Shen H Y, Zhang H Q, Gu N. Colloids Surf A,
References
[1] Frenanez I, Khiar N. Chem Rev, 2003, 103: 3651
[2] Wan M W, Yen T F. Appl Catal A, 2007, 319: 237
[3] Etemadi O, Yen T F. J Colloid Interface Sci, 2007, 313: 18
[4] Jiang Z X, Lü H Y, Zhang Y N, Li C. Chin J Catal, 2011, 32: 707
[5] Zhang Y N, Wang L, Zhang Y L, Jiang Z X, Li C. Chin J Catal, 2011, 32:
235
[6] Jiang C Y, Wang J J, Wang S T, Guan H Y, Wang X H, Huo M X. Appl
Catal B, 2011, 106: 343
[7] Komintarachat C, Trakarnpruk W. Ind Eng Chem Res, 2006, 45:
1853
[8] Yazu K, Yamamoto Y, Furuya T, Miki K, Ukegawa K. Energy Fuels,
2001, 15: 1535
[9] Tang N F, Zhao X P, Jiang Z X, Li C. Chin J Catal, 2014, 35: 1433
[10] Wishart J F. Energ Environ Sci, 2009, 2: 956
[11] Wilfred C D, Kiat C F, Man Z, Bustam M A, Mutalib M I M, Phak C Z.
Fuel Process Technol, 2012, 93: 85
[12] Li H M, Zhu W S, Wang Y, Zhang J T, Lu J D, Yan Y S. Green Chem,
2009, 11: 810
Graphical Abstract
Chin. J. Catal., 2015, 36: 1342–1349 doi: 10.1016/S1872-2067(15)60862-2
Selective oxidation of sulfurs and oxidation desulfurization of
model oil by 12-tungstophosphoric acid on cobalt-ferrite
nanoparticles as magnetically recoverable catalyst
Ezzat Rafiee*, Nasibeh Rahpeyma
Razi University, Iran
CoFe@Si-PW
CoFe@Si-PW catalyst was successfully used for the selective oxidation
of sulfides to their corresponding sulfones under mild reaction condi-
tions. The catalyst also showed high activity for oxidative desulfuriza-
tion of model oil.

Ezzat Rafiee et al. / Chinese Journal of Catalysis 36 (2015) 1342–1349
1349
2003, 212: 219
[43] Venkat Reddy C, Verkade J G. J Mol Catal A, 2007, 272: 233
[34] Haw C Y, Chia C H, Zakaria S, Mohamed F, Radiman S, Teh C H,
Khiew P S, Chiu W S, Huang N M. Ceram Int, 2011, 37: 451
[35] Morais P C, Santos R L, Pimenta A C M, Azevedo R B, Lima E C D.
Thin Solid Films, 2006, 515: 266
[36] Rakjumar T, Rao G R. J Chem Sci, 2008, 120: 587
[37] Sofia L T A, Krishnan A, Sankar M, Kala Raj N K, Manikandan P,
Rajamohanan P R, Ajithkumar T G. J Phys Chem C, 2009, 113: 21114
[38] Rafiee E, Eavani S, Rashidzadeh S, Joshaghani M. Inorg Chim Acta,
2009, 362: 3555
[44] Rafiee E, Baltork I M, Tangestaninejad S, Azad A, Moinee S. Z
Naturforsch B, 2006, 61: 601
[45] Zhang J, Wang A J, Li X, Ma X H. J Catal, 2011, 279: 269
[46] Chotani G, Dodge T, Hsu A, Kumar M, LaDuca R, Trimbur D, Weyler
W, Sanford K. Biochim Biophys Acta-Protein Struct Molec Enzym,
2000, 1543: 434
[47] Thomsen A B, Laturnus F. J Hazard Mater, 2001, 81: 193
[48] Zhao W, Zhang Y S, Ma B C, Ding Y, Qiu W Y. Catal Commun, 2010,
11: 527
[39] Gyergyek S, Makovec D, Kodre A, Arcon I, Jagodic M, Drofenik M. J
Nanopart Res, 2010, 12: 1263
[40] Martinez B, Obradors X, Balcells L, Rouanet A, Monty C. Phys Rev
Lett, 1998, 80: 181
[41] Sreedha B, Radhika P, Neelima B, Hebalkar N, Mishra A K. Catal
Commun, 2008, 10: 39
[42] Sheikhshoaie I, Rezaeifard A, Monadi N, Kaafi S. Polyhedron, 2009,
28: 733
[49] Zhang Z X, Zhao W, Ma B C, Ding Y. Catal Commun, 2010, 12: 318
[50] Long Z Y, Yang C P, Zeng G M, Peng L Y, Dai C H, He H J. Fuel, 2014,
130: 19
[51] Julião D, Gomes A C, Pillinger M, Cunha-Silva L, de Castro B, Gon-
çalves I S, Balula S S. Fuel Process Technol, 2015, 131: 78
[52] Zhao N, Li S W, Wang J Y, Zhang R L, Gao R M, Zhao J S, Wang J L. J
Solid State Chem, 2015, 225: 347
[53] Wu N J, Li B S, Liu Z X, Han C Y. Catal Commun, 2014, 46: 156