Synthesis and non-parametric evaluation studies on high performance of catalytic oxidation-extraction desulfurization of gasoline using the novel TBAPW11Zn?TiO2?PAni nanocomposite

Article abstract of DOI:10.1002/aoc.5299

In this work, the new catalyst (assigned as TBAPW₁₁Zn?TiO₂?PAni) was successfully designed and synthesized on the basis of quaternary ammonium salt of zinc monosubstituted phosphotungstate [(n-C₄H₉)₄N][PW₁₁ZnO₃₉] (TBAPW₁₁Zn), titanium dioxide (TiO₂), and polyaniline (PAni). This study reports the catalytic oxidation-extraction desulfurization (ECODS) of sulfur-containing molecules from real and the simulated (Th, BT, and DBT) gasoline using new organic–inorganic hybrid catalyst (TBAPW₁₁Zn?TiO₂?PAni). The ECODS results were shown that the concentration of sulfur compounds (SCs) of real gasoline was lowered from 0.4992 to 0.0122 wt.% with 97% efficiency at 35 °C after 1 h. Furthermore, the synthesized heterogeneous nanocatalyst showed high stability and reusability after five times without significant loss of activity. The high performance of TBAPW₁₁Zn?TiO₂?PAni/H₂O₂/CH₃CO₂H system can be a promising route with a superb potential in the generation of ultra-low-sulfur gasoline. Also the Mann–Whitney U-test results show that there is not a significant difference between the mean of sulfur percentage for DBT & BT, BT & Th and DBT & Th in the presence of the catalyst. Based on the Kruskal–Wallis test results, we can conclude that the temperature, time and amount of catalyst have a significant effect on ECODS efficiency of TBAPW₁₁Zn?TiO₂?PAni nanocomposite.

Full text of DOI:10.1002/aoc.5299

Received: 24 July 2019
DOI: 10.1002/aoc.5299
Revised: 9 September 2019
Accepted: 19 September 2019
F U L L P A P E R
Synthesis and non‐parametric evaluation studies on high
performance of catalytic oxidation‐extraction
desulfurization of gasoline using the novel
TBAPW11Zn@TiO2@PAni nanocomposite
Mohammad Reza Khanmohammadi Khorrami | Zahra Shokri Aghbolagh
Department of Chemistry, Faculty of
In this work, the new catalyst (assigned as TBAPW11Zn@TiO2@PAni) was
successfully designed and synthesized on the basis of quaternary ammonium
salt of zinc monosubstituted phosphotungstate [(n‐C4H9)4N][PW11ZnO39]
(TBAPW11Zn), titanium dioxide (TiO2), and polyaniline (PAni). This study
reports the catalytic oxidation‐extraction desulfurization (ECODS) of sulfur‐
containing molecules from real and the simulated (Th, BT, and DBT) gasoline
using new organic–inorganic hybrid catalyst (TBAPW11Zn@TiO2@PAni). The
ECODS results were shown that the concentration of sulfur compounds (SCs)
of real gasoline was lowered from 0.4992 to 0.0122 wt.% with 97% efficiency at
35 °C after 1 h. Furthermore, the synthesized heterogeneous nanocatalyst
showed high stability and reusability after five times without significant loss
of activity. The high performance of TBAPW11Zn@TiO2@PAni/H2O2/
CH3CO2H system can be a promising route with a superb potential in the gen-
eration of ultra‐low‐sulfur gasoline. Also the Mann–Whitney U‐test results
show that there is not a significant difference between the mean of sulfur per-
centage for DBT & BT, BT & Th and DBT & Th in the presence of the catalyst.
Based on the Kruskal–Wallis test results, we can conclude that the tempera-
ture, time and amount of catalyst have a significant effect on ECODS efficiency
of TBAPW11Zn@TiO2@PAni nanocomposite.
Science, Imam Khomeini International
University, Qazvin, Iran
Correspondence
Mohammad Reza Khanmohammadi
Khorrami, Department of Chemistry,
Faculty of Science, Imam Khomeini
International University, Qazvin, Iran.
Email: m.khanmohammadi@sci.ikiu.ac.ir
KEYWORDS
catalytic oxidation‐extraction desulfurization, heterogonous catalyst, Polyaniline, Polyoxometalates,
titanium dioxide
1 | INTRODUCTION
stringent regulations have been imposed to limit the
SCs of liquid fuels to a very low level.[2] In the EU, actu-
Presence of high levels of SCs in transportation fuels are
an important source causing temperature inversion,
global climate changes and acid rain. It is necessary to
remove SCs from fuels to avoid SOx emissions during
the burning of petroleum fractions.[1] In order to fulfill
the goal of reducing the air pollution, increasingly
ally the SCs of gasoline is approximately below 10 ppm.[3]
Hydro desulfurization procedure works at severe operat-
ing conditions (at 320–380 °C, 30–70 atm of hydrogen
pressure and large reactor volume), and has not ideal per-
formance in removing refractory SCs such as
dibenzothiophene (DBT) and their sterically hindered
Appl Organometal Chem. 2019;e5299.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
1 of 14
https://doi.org/10.1002/aoc.5299

2 of 14
KHORRAMI AND AGHBOLAGH
derivatives.[4] Oxidative desulfurization has drowned
extensive attention as one of the most cost‐effective sys-
tem for elimination of aromatic sulfur‐containing com-
pounds under mild operating conditions and it does not
require expensive hydrogen.[5]
As a part of our continued efforts to improve the HPAs
preparation and application,[23–25] herein we report
the synthesis a new type of phase transfer catalyst
TBAPW11Zn@TiO2@PAni as an effective hybrid catalyst
for ECODS of real and simulated gasoline. The catalyst
was synthesized at ambient temperature and was
characterized by elemental analysis, FT‐IR, SEM, XRD,
UV–Vis, and EDX methods. The mixture of H2O2/
CH3CO2H (in v/v ratio of 2:1) was used
as an oxidant and polar acetonitrile utilized as an
extraction solvent. Very interestingly, we found that
TBAPW11Zn@TiO2@PAni nanocomposite could oxidize
sulfur to sulfoxide and sulfone[10] under mild
conditions. Also, the effect of different factors on the
ECODS efficiency, probable oxidation reaction mecha-
nism, the Mann–Whitney U‐test and the kinetic of
the ECODS process is studied in detail. The
TBAPW11Zn@TiO2@PAni nanocatalyst showed a signif-
icant improved catalytic performance in ECODS of gas-
oline and simulated fuel.
The literature related to the selective oxidation of
organic sulfur‐containing molecules to their correspond-
ing sulfoxides/sulfones through the reaction of hydrogen
peroxide and short‐chain carboxylic acids introduced it
as an effective oxidizing system.[6,7] Heteropoly Acids
(HPAs) as a unique class of anionic metal‐oxo clusters
has received a lot of attention for catalysis of the ODS
process over the past decade.[8,9] More recently, com-
bined oxidation‐extraction desulfurization process
(ECODS) is regarded as one of the most appropriate
and effective methods due to its unique sulfur removal
efficiency.[10] Among the different varieties of their
structures, Keggin HPAs have shown excellent catalytic
activity in oxidative desulfurization reactions due to
the numerous terminal oxygen atoms.[11,12] The applica-
tion and effective separation and reusability of the
HPAs‐based heterogeneous catalysts are limited because
of their high solubility in the polar medium and low
specific surface areas.[13] In order to overcome these
drawbacks, the synthesis of HPAs‐supported catalysts
or complexation with an organic or inorganic cation
has been explored in recent years.[14] Recently, the
incorporation of HPAs and TiO2 has been considered
as a promising strategy to enhance the catalytic activity
of the metal‐oxygen clusters because of its poorly solu-
ble, and low toxicity particles.[15,16] Furthermore, there
has been growing interest in using PAni as a various
carrier material for improving the catalytic efficiency
of catalysts in heterogeneous system due to the its inter-
esting redox properties, easy synthesis route, chemical
stability, and low cost.[17–20] Besides, the incorporation
of PAni and inorganic metal oxides have been shown
to be a very efficient method to increase the catalytic
performance and to improve physical, mechanical, and
electrical properties.[21] All of the above mentioned rea-
sons make the organic PAni polymer and inorganic
TiO2 particles as a promising organic–inorganic hybrid
substrate for immobilization of HPAs. Hydrogen perox-
ide (H2O2) is mostly chosen as an environmentally
benign oxidant for oxidation of organic compounds
due to the only by‐product is water.[22] Aqueous H2O2
is not soluble in the oil phase that including SCs. There-
fore we carried out the ECODS reaction using phase
transfer catalysts to provide a green and effective oxida-
tion process of fuel oil. In other words, in order to facil-
itate the transition of the HPAs into organic phase,
counteraction with quaternary ammonium salt with
lipophilic cation was used as a phase transfer agent.
2 | EXPERIMENTAL
2.1 | Materials and analytical
characterization
Sodium tungstate dihydrate (Na2WO4.2H2O), disodium
phosphate (Na2HPO4), zinc nitrate (Zn (NO3)2, aniline,
ammonium peroxydisulfate ((NH4)2S2O8), hydrogen per-
oxide (H2O2, 30 vol%), ethanoic acid (CH3CO2H), acetoni-
trile (MeCN) and tetrabutylammonium bromide (TBAB),
thiophene (Th), benzothiophene (BT), dibenzothiophene
(DBT), and solvent (n‐heptane) were obtained Sigma‐
Aldrich. All aqueous solutions were prepared using dou-
ble distilled water (DDW). Typical real gasoline
(0.7979 g.ml−1 of density at 15 °C, total sulfur content of
0.4992 wt.%) was used. The Fourier transform infrared
(FT‐IR) spectra were taken with a Thermo‐Nicolet‐iS10
spectrometer in the range of 400–4000 cm−1 with KBr
disks. Ultraviolet visible (UV–vis) spectra were measured
with a double beam Thermo‐Heylos spectrometer. The
surface morphology was analyzed using scanning
electron microscope (SEM; LEO 1455 VP). The composi-
tion of TBAPW11Zn@TiO2@PAni composite was also
assessed by energy dispersive X‐ray analysis measure-
ments (EDX). The X‐Ray powder Diffraction (XRD) was
performed by D8 Bruker Advanced, X‐ray diffractometer
using Cu K Alpha radiation (α = 1.54 Å) and the data
were collected between 2θ = 5–80°. The total sulfur and
mercaptan contents in gasoline before and after ECODS
reaction were obtained using X‐ray fluorescence with a

KHORRAMI AND AGHBOLAGH
3 of 14
TANAKA RX‐360 SH X‐ray fluorescence spectrometer
(ASTM D‐4294 and D‐3227, respectively).
of simulated gasoline, 50 ml of gasoline, 0.1 g of
TBAPW11Zn@TiO2@PAni, 10 ml of MeCN as an extract-
ant and H2O2/CH3CO2H as an oxidant and in the volume
ratio of 2:1 (3 ml) were stirred regularly for 1 hr at 35 °C
and were added to round‐bottomed flask equipped with
stirring hot plates. Consequently, the gasoline was
extracted to calculate recovery percentage (for two times
reaction: 95 and 94%). The amount of total sulfur and
mercaptan content in an oil phase before and after
ECODS were determined by a TANAKA SIENTIFIC
RX‐360 SH X‐ray fluorescence spectrometer (ASTM D‐
4294 and D‐3227, respectively). Results for the desulfuri-
zation are listed in Table 1.
2.2 | Catalytic tests
2.2.1 | Desulfurization of simulated fuel
by TBAPW11Zn@TiO2@PAni catalysts
In order to evaluate the catalytic activity of the synthe-
sized catalyst, simulated fuel was generated through sim-
ple mixing of DBT, BT, Th and n‐heptane, separately,
with the initial SCs of 500 ppm by weight recorded for
all of them. The TBAPW11Zn@TiO2@PAni nanocompos-
ite, H2O2/CH3CO2H (3 ml) in ratio of 2:1, and simulated
fuel was added in a 250‐ml round‐bottom flask in experi-
mental proportion, which was placed in a thermostatic
water bath at particular temperature (25–40 °C) and was
stirred vigorously by stirring hot plates. The oxidized
SCs were extracted using MeCN in the volume ratio of
1:5 (MeCN/SCs) by a separating funnel. After the
ECODS, the upper clear phase (simulated fuel) was ana-
lyzed for total sulfur and mercaptan using a TANAKA
SIENTIFIC RX‐360 SH X‐ray fluorescence spectrometer
(ASTM D‐4294 and D‐3227, respectively). The ECODS
efficiency of simulated gasoline is calculated simply by
the following equation Equation (1), where CSi and CSf
are initial and final concentration of simulated gasoline
after time t, respectively.
2.3 | Preparation of catalyst
2.3.1 | Preparation of [(n‐C4H9)4N]
[PW11ZnO39]
[PW11ZnO39]q‐ was synthesized according to the reported
methods.[25–27] Briefly, Na2WO4.2H2O (6 gr), Na2HPO4
(6 gr) and Zn (NO3)2 (1 gr) were added to 50 ml of
DDW, and pH of the mixture was adjusted to 4.7. Based
on the literature,[28] an aqueous solution of TBAB (5 gr
in 20 ml) was added drop wise under stirring, and then
was heated to 80 °C. Ultimately, the obtained solid was
filtered and dried (assigned as TBAPW11Zn).
2.3.2 | Preparation of TBAPW11Zn@TiO2
CSi − CSf
ECODS efficiency% ¼
× 100
(1)
CSi
In a typical procedure, 0.05 g of TiO2 was dispersed in
25 ml of acetic acid (2%) then 0.05 g of synthesized
TBAPW11Zn was dissolved in 5 ml boiling DDW and
added into the reaction vessel slowly. The mixed solution
was heated to 60 °C with stirring for 1 hr. After the
removal of water through evaporation, a white gel was
formed. Then it was aged at 90 °C for 2 hr to obtain a
powder form of TBAPW11Zn@TiO2.
2.2.2 | Desulfurization of real gasoline by
TBAPW11Zn@TiO2@PAni catalysts
In order to verify the ECODS efficiency, similar to the
experimental procedure done for the desulfurization
TABLE 1 Catalytic oxidation‐extraction desulfurization of gasoline by TBAPW11Zn@TiO2@PAni
Analysis
Properties of
gasoline
Test
Method
Before
ECODS
After
ECODSa
Entry
Unit
1
2
3
Mercaptans
ppm
Wt. %
cP
ASTM D 3227
ASTM D 4294
ASTM D 7042
95
3
Total Sulphur Contents
Dynamic Viscosity
0.4992
0.0122
@15°C
0.79
0.68
0.77
0.66
4
5
6
Density by hydrometer @15°C
Surface Tension
@20°C
@15°C
@15°C
g/ml
ASTM D 1298
ASTM D 1331
ASTM D 971
0.7987
20.4
0.7985
20.3
mN/m
mN/m
Interfacial Tension
18.0
17.8
aCondition of ODS process: 50 ml of gasoline, 0.10 g of catalyst, 3 ml of oxidant, 10 ml of acetonitrile, reaction temperature = 35 °C, and reaction time = 1 hr.

4 of 14
KHORRAMI AND AGHBOLAGH
2.3.3 | Preparation of
TBAPW11Zn@TiO2@PAni catalyst
n2ðn2 þ 1Þ
U2 ¼ n1n2 þ
− R2
(3)
2
The TBAPW11Zn@TiO2@PAni was synthesized by in situ
chemical oxidation polymerization of aniline monomer in
the presence of TBAPW11Zn@TiO2 solution. In a typical
synthesis, 1 ml of aniline and 1 gr of TBAPW11Zn@TiO2
were added to 60 ml DDW under ultrasonic conditions
using an ultrasonic water bath (frequency 35 kHz mains
connection 230 V) for 30 min. The polymerization reac-
tion was initiated immediately after the addition of
(NH4)2S2O8 (2.20 g) to the above solution. The mixture
was allowed to react for 10 hr under constant stirring.
The obtained dark gray solid (TBAPW11Zn@TiO2) was
rinsed thoroughly (3 times) with DDW and finally dried
at 70 °C for 4 hr.
3 | RESULTS AND DISCUSSION
3.1 | Characterization studies
Infrared spectroscopy of TBAPW11Zn, TiO2, PAni and
TBAPW11Zn@TiO2@PAni, are shown in Figures 1, 2 and
Table 2. The origins of the vibration peaks are as follows:
The characteristic bands of Keggin‐type polyoxoanion
[TBAPW11Zn] is confirmed by characteristic absorption
bands of Zn–O, W–O terminal (W = Ot) and W–O bridg-
ing groups (W–Ob–W, W–Oc–W) at 1049, 951, 889, and
2.4 | Computational section
The assumption for the normal distribution is that the
mean and the standard deviation reflect the measures
related to the central tendency and the dispersion of the
studied data, respectively. In distribution‐free methods
(non‐parametric) that are introduced in this study, there
are no assumptions about the distribution of the popula-
tion. Moreover, the non‐parametric tests are considered
to be the robust methods due to their resistance to outly-
ing observations, which greatly influence on the mean
and the standard deviation. In this study, a suitable
non‐parametric test was selected.
FIGURE
TBAPW11Zn@TiO2
1
FT‐IR of a) TiO2, b) TBAPW11Zn and c)
2.4.1 | The Mann–Whitney U‐test
The Mann–Whitney U‐test is one of the most powerful
nonparametric tests used for recognizing two distribution
functions. The Mann–Whitney U‐test is a strong alterna-
tive to the parametric independent‐samples t‐test. The
hypothesis tested by the Mann–Whitney analysis is that
the medians of the two groups are equal and no true dif-
ference between both samples. In this situation, the ranks
for two groups should appear at random. Otherwise,
there is a significant difference between the median of
two groups. According to this test, first, all the existing
data are taken together considered and are ranked.
The test allows comparison of the calculated smaller u
Equation (2) and (3) with the critical value for U.
n1 ðn1 þ 1Þ
FIGURE 2 FT‐IR of a) TBAPW11Zn@TiO2, b) PAni and c)
TBAPW11Zn@TiO2@PAni
U1 ¼ n1n2 þ
− R1
(2)
2

KHORRAMI AND AGHBOLAGH
5 of 14
807 cm− 1, respectively[29] The sharp signal at 1084 cm− 1
is related to the P–O a stretching bonds of the PO4 tetra-
hedra (Figure 1b).[30] As shown in Figure 2(b), pure PAni
(emeraldine) salt showed the vibrational frequency at
1522 and 1648 cm−1, which is attributed to the C–C vibra-
tion of benzenoid and quinonoid ring, respectively.[31]
The characteristic Keggin‐structured bonds were
also located distinctively for TBAPW11Zn@TiO2
(Figure 1c) and TBAPW11Zn@TiO2@PAni (Figure 2c).
For TBAPW11Zn@TiO2@PAni, four HPAs characteristic
peaks appear with only slight shifts compared to the pure
TBAPW11Zn, and the peaks which are observed in the
range of 468–702 cm−1 and around 1464 cm−1 are attrib-
uted to the Ti‐O bond of TiO2 indicating the formation of
the TBAPW11Zn@TiO2@PAni hybrid through strong
electrostatic interaction.[15]
The spectrum of TBAPW11Zn indicated an intense
absorption peak at 255 nm. As shown in PAni spectrum
(Figure 3b), the characteristic absorption bands at
242 nm is assigned to the π → π* transition of the benze-
noid ring and the second one in 321 nm is attributed to
n → π* excitation transition of the quinonoid ring[21]
The characteristic peak was indicated at 255 nm assigned
to O2− → W6+ charge transfer (LMCT) of TBAPW11Zn
(Figure 3a), 260 nm for TBAPW11Zn@TiO2@PAni
(Figure 3c) which showed slight shifts in the modified
synthesized hybrid nanocatalyst. This shifts proved the
intermolecular
electronic
interactions
between
TBAPW11Zn, TiO2, and PAni. Investigation of the UV–
vis spectrum is in good agreement with the results of
FT‐IR.
FIGURE 3 The UV–Vis spectra of a) TBAPW11Z, b) PAni and c)
TBAPW11Zn@TiO2@PAni
TABLE 2 FT‐IR peaks of TBAPW11Zn@TiO2@PAni, TBAPW11Zn@TiO2 and TBAPW11Zn
Wavenumber (cm−1
Compounds
)
TBAPW11Zn@TiO2
TBAPW11Zn
TBAPW11Zn@TiO2@PAni
Vibration mode
1031
1038
1049
Streching of Zn‐O
3431–3456
‐
‐
Streching of N‐H
952
1006
1084
ν (P‐Oa)
881
887
889
ν (W = Ot)
830
‐
807
ν (W–Ob–W) & ν (W–Oc–W)
Anti‐symmetric Ti–O–Ti
C‐H stretching
1464
1402
‐
‐
‐
‐
‐
‐
2852 to 2923
510
505
‐
‐
‐
‐
C‐H out‐of‐plane bending vibration
Streching of C=N & C=C
Streching of C–N benzenoid ring
1558, 1577–1581, 1481–1485
1298–1301, 1242–1245
1114–1126
In‐plane bending vibrations of C–H mode of
quinonoid (N = Q = N) & benzenoid ring

6 of 14
KHORRAMI AND AGHBOLAGH
The X‐ray diffraction pattern of TBAPW11Zn,
low degree of crystallinity.[32] Amorphous nature of PAni
is due to the scattering from the PAni chains at
interplanar spacing. [33] As shown in Figure 5, diffraction
peaks related to PAni are not detected in the
TBAPW11Zn@TiO2@PAni catalyst. This result indicated
that the degree of crystallinity of PAni chain has been
hampered in TBAPW11Zn@TiO2@PAni hybrid.[33,34]
When TBAPW11Zn@TiO2 nanocomposite are added on
the surface of titanium dioxide, due to the restrictive
effect of TiO2 nanoparticles the degree of crystallinity of
PAni is compromised.[35] By comparing the X‐ray diffrac-
tion patterns of TBAPW11Zn@TiO2@PAni hybrid
nanocatalystwith that of pure TBAPW11Zn, TiO2 and
PAni, it could be found that the sharp peaksat 24.70°,
38.22°, 47.60° and 54.11° are due to (110), (101), (111)
and (211) crystal planes of anatase titanium dioxide and
HPAs revealed at 7–45° showing the presence of TiO2
and TBAPW11Zn in PAni.[36] In addition, the XRD pat-
terns of hybrids TBAPW11Zn@TiO2@PAni are in good
agreement with primary TBAPW11Zn, revealing that the
Keggin structure of TBAPW11Zn remains intact in the
hybrids (Figure 5c). The crystallite size of
TBAPW11Zn@TiO2@PAni was calculated by the Debye–
Scherrer equation Equation (4).
TBAPW11Zn@TiO2 and TBAPW11Zn@TiO2@PAni were
collected and presented in Figures 4 and 5. The peaks
for balk TBAPW11Zn at 7–10 °, and 16–42° showed
Keggin‐type of HPAs.[29] The XRD patterns of the PAni
showed two broad peaks at 20.2° and 25.4° indicating
FIGURE 4 XRD pattern of a) TiO2, b) TBAPW11Zn and c)
TBAPW11Zn@TiO2
D ¼ K λ= βcos θ
(4)
where D is the average crystallite size, K is equal to 0.89, λ
is the wavelength of X‐ray (1.5406 Å), β is the Full Width at
Half Maximum (FWHM) intensity of the peak, and θ is the
half of the diffraction angle.[37] With respect to equation,
the average size of the TBAPW11Zn@TiO2@PAni nano-
composite is estimated to be about 80.9 nm.
The surface morphology of the sample was recorded by
SEM. It is interesting to note that, the SEM images
(Figure 6) exhibit sphere‐like structures with a mean par-
ticle size of ∼75 nm for TBAPW11Zn@TiO2@PAni
catalyst.
As evidenced clearly from the EDX results, the
presence of the Ti, W and Zn elements in the nanocom-
posite structure proved the successful synthesis of
FIGURE 5 XRD pattern of a) TBAPW11Zn@TiO2, b) PAni and c)
TBAPW11Zn@TiO2@PAni
FIGURE 6 SEM images of (a) PAni (b) TiO2 and (c) TBAPW11Zn@TiO2@PAni

KHORRAMI AND AGHBOLAGH
7 of 14
TBAPW11Zn@TiO2@PAni (Figure 7). The amounts of
Ti, W, Zn, C, N, O and P elements were equal to
30.60, 1.47, 0.07, 19.72, 5.22, 41.86 and 1.07 wt%, respec-
tively. Furthermore, other chemical characterization was
recorded by elemental chemical analysis (Table 3).
3.2.2 | The effect of different sulfur com-
pounds on the ECODS reaction
This study proved the excellent catalytic activity of
TBAPW11Zn@TiO2@PAni in the proprietary elimination
of Th, BT, and DBT from n‐heptane under the previously
mentioned conditions. The oxidation reactivity of the
simulated gasoline at the same condition followed the
order of DBT > BT > Th, due to the higher electron den-
sity of sulfur atom in DBT compared with those in BT
and Th. As can be concluded from the literature, the oxi-
dation efficiency of SCs increased with the increase of the
electron density of sulfur atom [20,27]. In the presence of
TBAPW11Zn@TiO2@PAni as catalyst and H2O2/
CH3CO2H as oxidant agent, DBT, BT, and Th are oxi-
dized with 99%, 98%, and 97% efficiencies, respectively.
According to the Figure 8, the presence of H2O2/
CH3CO2H (in v/v ratio of 2:1) as oxidant has a significant
effect on the desulfurization efficiency, which is due to
the formation of CH3CO3H (peroxide acid) as a supplier
source of active oxygen.[37] Also a comparative desulfuri-
zation test without CH3CO2H (with H2O2, 3 ml as oxi-
dant) was shown the negligible conversion of sulfur
compounds (see Table 4).
3.2 | ECODS process results
3.2.1 | Desulfurization of real gasoline
So, in order to prove the superior catalytic activity of
TBAPW11Zn@TiO2@PAni, the exclusion of SCs from
real gasoline was performed. It is interesting to note
that, the elimination of mercaptan and total sulfur con-
tents from gasoline after desulfurization reaction has a
considerable efficiency, while other features of fuel
remained unaffected, meaning that the new synthesized
composite in this work had superb utilization of
CH3CO2H/H2O2 (see Table 1). X‐ray fluorescence spec-
trometer analysis showed that total SCs (wt %) of gaso-
line could decrease from 0.4992 wt.% to 0.0122 wt.% and
the mercaptans were reached from 95 ppm to 3 ppm.
The reason was due to the high performance of
TBAPW11Zn@TiO2@PAni as a catalyst for ECODS
system.
3.2.3 | The effect of the time and temper-
ature on the ECODS reaction
In order to determine the effect of different times and
temperatures on the catalytic activity of synthesized cata-
lyst, a series of desulfurization experiments were per-
formed, and the results were presented in Figure 9.
Four temperatures were tested (25°, 30°, 35° and 40 °C).
It is proved that the activity of present oxidative desulfur-
ization is increased mainly with the increasing tempera-
ture. After 1 hr, the desulfurization efficiency from Th,
BT and DBT at 35 °C was found to be by 97, 98 and
99% respectively. Based on the results, increasing the pro-
cess temperature to 40 °C or above did not have a signif-
icant effect on the conversion of simulated fuel to their
corresponding sulfones. Thus, the temperature of 35 °C
was chosen as an optimum temperature in the ECODS
system.
FIGURE 7 EDAX analysis of TBAPW11Zn@TiO2@PAni
TABLE 3 Elemental analysis of catalysts
Catalyst
Data
K
P
W
Zn
C
N
H
K4[PW11ZnO39]
Calcd (mass%)
Exp. (mass%)
Calcd (mass%)
Exp. (mass%)
5.44
1.08
0.98
1.03
0.92
70.46
70.34
67.74
67.63
2.28
2.17
2.19
2.07
‐
‐
‐
5.32
‐
‐
‐
((n‐C4H9)4N)4[PW11ZnO39]
‐
‐
6.43
6.33
0.46
0.35
1.21
1.11

8 of 14
KHORRAMI AND AGHBOLAGH
FIGURE 8 The results of ECODS of real gasoline, DBT, BT, and
Th with oxidant and without it
FIGURE 9 Effect of different time and temperature on ECODS
of Th, BT and DBT
TABLE 4 Effect of different desulfurization system on sulfur removal from model fuela
Sulfur removal%
DBT
Entry
Desulfurization system
Th
BT
1
2
3
TBAPW11Zn@TiO2@PAni
75.2
93.8
99
74.9
90.8
97
75.8
92.1
98
TBAPW11Zn@TiO2@PAni/H2O2 (3 ml)
TBAPW11Zn@TiO2@PAni/H2O2/CH3CO2H (in v/v ratio of 2:1)
aCondition of ODS process: 50 ml of model fuel (500 ppmw of Th, BT, and DBT in n‐heptane), 0.10 g of catalyst, 10 ml of acetonitrile, reaction tempera-
ture = 35 °C, and reaction time = 1 hr.

KHORRAMI AND AGHBOLAGH
9 of 14
TABLE 6 Effect of different catalysts in oxidation desulfurization
of different sulfur compoundsa
3.2.4 | The effect of the catalyst amounts
on the ECODS reaction
Conversion %
As can be seen in Table 5, the amount of catalyst has a
significant effect on the sulfur removal efficiency. Fur-
thermore, the conversion of simulated fuel into their cor-
responding sulfones was enhanced quickly along with the
reaction time. Amount of catalyst was optimized by
changing it from 0.02 gr to 0.12 gr. When 0.1 gr of
TBAPW11Zn@TiO2@PAni was applied maximal sulfur
removal was achieved. In the same manner, 13, 15, 16
and 13% of Th, BT, DBT and gasoline were eliminated
in the absence of catalyst as a blank test. When the con-
centration level of the catalyst was enhanced to 0.12 g,
no significant changes were found in desulfurization rate.
The reason may be due to the prevention of sulfide
adsorption and oxidation onto catalyst due to the accu-
mulation of the metal‐oxo and metal‐peroxo species. Ulti-
mately, 0.1 gr of catalyst was chosen as a suitable amount
in the ECODS reaction system.
Entry Catalyst
DBT Th BT Ref.
[37]
1
H7SiV3W9O40
92
78
60
58
58
95
97
96
35
98
95
94
79
32
‐
‐
93
75
[37]
[38]
[38]
[37]
[39]
[40]
[19]
[19]
[19]
[21]
2
H3PMo12O40
K3PW12O40
3
58 59
56 56
4
K4SiW12O40
H6P2W18O62
PMo@HKUST‐1
HPMo@SiO2
HPW‐TiO2‐SiO2
PAni
5
‐
90
‐
52
‐
6
8
‐
9
‐
‐
10
11
12
13
14
15
16
17
18
19
20
38 34
97 98
92 93
PW11Mn/NiO/PAN
CTAB‐PTA@CS
PW11Zn@TiO2
TBAPW11Zn
TiO2
91 92 This Work
74 77 This Work
24 27 This Work
97 98 This Work
13 15 This Work
TBAPW11Zn@TiO2@PAni 99
3.2.5 | The effect of different catalysts on
the ECODS reaction
Blank Test
16
61
69
71
[36]
TBA‐SiW12O40
TBA‐Si2W18Mn4
PW11Mn
59 60
[36]
As a comparison, the effect of various HPAs‐based cata-
lysts on the removal of SCs content in the desulfurization
reaction was evaluated and the results were listed in
Table 6. Blank test was carried out in the absence of
TBAPW11Zn@TiO2@PAni as a catalyst. It was found that
in the absence of catalysts % conversion was very low. With
respect to the results, TBAPW11Zn is more effective than
K3PW12O40 (Table 6, entry 3) and K3PMo12O40 (Table 6,
entry 2) samples. Also, the ability of pure TiO2 in removal
of total sulfur content was found negligible (Table 6, entry
66 68
[19]
69 68
aCondition of ODS process: 50 ml of gasoline or model fuel (500 ppmw of Th,
BT, and DBT in n‐heptane), 0.10 g of catalyst, 3 ml of oxidant, 10 ml of ace-
tonitrile, reaction temperature = 35 °C, and reaction time = 1 hr.
15), although the synthesized TBAPW11Zn@TiO2@PAni
composite is demonstrated significant performance in
ECODS process. Fortunately, among all the catalytic desul-
furization experiments, the ECODS reaction with
TBAPW11Zn@TiO2@PAni composite showed the highest
catalytic efficiency (Table 6, entry 16).
TABLE 5 Effect of Catalyst dosage on the ECODS of simulated
and actual gasolinea
Conversion (%)
Amount of
Entry catalyst (gr) Actual Gasoline DBT BT Th
3.2.6 | The suggested mechanism of the
oxidative desulfurization
1
0 (Blank)
0.02
13
27
46
60
89
98
98
16
32
48
71
90
99
90
15
29
47
68
90
98
98
13
27
45
67
88
97
97
In order to get an insight into the ECODS reaction, we
propose a mechanism for the activation of HPAs‐based
catalyst which was put forward. As shown in Scheme 1,
peracetic acid (CH3CO3H) is generated due to reaction
of hydrogen peroxide and glacial acetic acid as an active
oxygen source. In a second step, W=O of the TBAPW11Zn
is turned into the active W‐peroxide species (W (O2)) and
along with the reaction the oxygen is donated from
CH3CO3H. The W (O2) species oxidize the SCs, faster
than the W=O. Then, oxygen donated from W (O2) is
transferred to Th, BT, and DBT and the formation of
2
4
0.04
0.06
0.08
0.1
6
8
10
12
0.12
aCondition of ODS process: 50 ml of actual gasoline and simulated gasoline
(500 ppmw of Th, BT, and DBT in n‐heptane), 0.10 g of catalyst, 3 ml of oxi-
dant, 10 ml of acetonitrile, reaction temperature = 35 °C, and reaction
time = 1 hr.

10 of 14
KHORRAMI AND AGHBOLAGH
SCHEME 1 Suggested mechanism of the oxidative desulfurization by using CH3COOH/H2O2 as oxidant agent.
the transition states are thiophene sulfoxide (ThO),
benzothiophene sulfoxide (BTO), and dibenzothiophene
sulfoxide (DBTO). Then, W‐peroxide is turned to W=O
and reacts with CH3CO3H again for the next step. The
dC
dt
−
¼ kC
(6)
(7)
C dC
∫
C
ThO, BTO, DBTO are oxidized by W (O2) and ThO2,
¼ ln ¼ −kt
[10]
C
Co
C
o
BTO2, DBTO2
are generated and the W‐peroxide is
regenerated.[22,38] Therefore, the oxidation mechanism
of simulated oil and process of the desulfurization are
verified.
Communication between C and t can be defined by equa-
tion (8):
C ¼ Coe−kt
(8)
3.2.7 | Kinetics of oxidation reaction of
DBT, BT and Th
In this equation, C0 and Ct are the initial concentrations
and concentrations at time t, respectively. As shown in
Figure 10 and Equation 8, a linear relationship was
observed between (C/C0) and t. The correlation was
achieved close to unity (Table 7). The results approved
that the oxidation reaction kinetics fitted to the pseudo‐
first‐order model. Moreover, the affiliation of k on the
reaction temperature could be expressed by the well‐
known Arrhenius equation (Equation 9).[22]
The conversion results for the ECODS process were
appeared to obey the first‐order kinetic model. The kinet-
ics of oxidation of was investigated under multiple condi-
tions of experimental temperature ranging 25, 30, 35 and
40 °C. It is critical to note that, by increasing experimen-
tal temperature from 25 to 35 °C, removal of Th from 73
to 97%, BT from 74 to 97% and for DBT from 75 to 98% in
1 h is increased. The rate constant (k) was estimated
as follows Equation (7), on the basis of the first‐order
kinetics:
k ¼ Aeð−Ea=RTÞ
(9)
In the above equation, A is the Arrhenius frequency

KHORRAMI AND AGHBOLAGH
11 of 14
TABLE 7 Pseudo‐first‐order rate constants and correlation fac-
tors of the S‐PAC (Th, BT and DBT)
Rate constant
k (min−1
Correlation
factor R2
)
Temperature
(°C)
Th BT
DBT Th
BT
DBT
25
30
35
40
0.019 0.021 0.022 0.912 0.918 0.923
0.024 0.025 0.030 0.877 0.889 0.921
0.047 0.045 0.056 0.917 0.917 0.874
0.047 0.050 0.059 0.917 0.947 0.890
behind this behavior is due to the lowest aromatic p‐
electron density on the Th sulfur atom compared to those
in DBT and BT.
3.2.8 | Regeneration of catalyst phase
The long‐term stability of the TBAPW11Zn@TiO2@PAni
catalyst has remarkable importance for its industrial per-
formance. To obtain further insight into the regeneration
of the TBAPW11Zn@TiO2@PAni composite in the
ECODS process of DBT compounds, the following exper-
iments were done. Briefly in a typical reaction, the water
catalyst phase was reused in five consecutive experiments
by filtration; it was washed and dried at 25 °C. After test,
the desulfurization efficiency of the catalyst decreases
slightly from 99% in the first cycle to 94% in the fifth cycle
(The results are presented in Figure 12). Due to the prod-
uct accumulation and the decrease in pH value, we
observed the slight decrease in ECODS efficiency of the
catalyst system. Also, the oxidation product was
reextracted by dichloromethane. As Figure 13 the infra-
red spectroscopy had been proven to be DBT sulfone
(DBTO2).[39]
3.3 | Computational results and
discussion
FIGURE 10 Plots of C/C0 for the oxidation of a) Th, b) DBT and
c) BT
3.3.1 | The effect of the catalyst amounts
on the ECODS reaction
The introduced catalyst in the ECODS process is not
influenced by the structure of the sulfur‐containing com-
pounds. In other words, the synthesized catalyst
(TBAPW11Zn@TiO2@PAni) provides the possibility for
performing the ECODS on various sulfur‐containing
compounds. In order to prove this, the Mann–Whitney
U‐test were performed in different dosages of catalyst (0,
0.02, 0.04, 0.06, 0.08, 0.1 and 0.12), and the results are
as follows:
factor, Ea is the apparent activation energy, R is the uni-
versal gas constant and, Tis the reaction temperature (in
Kelvin) [38]. It should be noted that, the Arrhenius curves
and the apparent activation energy (Ea) for the ECODS of
DBT, BT and Th equal to were 49.511, 52.677 and
55.708 kJ.mol−1, respectively (see Figure 11 and Table 7
). The efficiency of the ECODS process for model gasoline
was increased in the order of DBT > BT > Th. The reason

12 of 14
KHORRAMI AND AGHBOLAGH
FIGURE 11 Arrhenius plot for the oxidation of a) Th, b) DBT and c) BT
Additionally, it can be proved that, there is not a signifi-
cant difference between the mean of sulfur percentage
for DBT & BT, BT & Th and DBT & Th in the presence
of the catalyst.
3.3.2 | The effect of the time and temper-
ature on the ECODS reaction
The Kruskal–Wallis analysis of SCs
The H0 was tested by the Kruskal–Wallis test upon
which, it is stated that the three instruction methods
have the same effect on the number of correct responses
achieved.[41] Thus, the samples are selected randomly
from the equal population distribution. The calculated
Kruskal‐Wallis statistic is explicated as a chi‐square
value and it is represented to be significant at p < 0.1,
and for DBT, BT and Th, the value of χ2 (df = 2) is
equal to 4.74, 4.76 and 5.00, respectively. According to
the number of correct responses calculated, it was found
that the three methods are not similarly effective
(because as shown in Table 9, the value of 4.61 is less
than the values of 4.74, 4.76 and 5.00), therefore, the
H0 is rejected. Thus, it was found that the temperature,
time and amount of catalyst have a significant effect
on ECODS efficiency of TBAPW11Zn@TiO2@PAni
nanocomposite.
FIGURE 12 Effect of the recycle times on the ECODS efficiency
by TBAPW11Zn@TiO2@PAni
The Mann–Whitney U‐test for SCs
Table 8 shows the comparison for the smaller of U test
values of the following two test‐statistics with the critical
value of U. The smaller of U test values for DBT & BT, BT
& Th and DBT & Th are equal to 20.5, 20.0 and 20.0,
respectively. As shown in Table 8, for a two‐sided test
with n1 = n2 = 7, the 5% level of U is equal to 8. Thus,
the null hypothesis (symbolized by H0) is accepted and
it can be concluded that, there is no evidence to prove
the difference between the two comparison groups.

KHORRAMI AND AGHBOLAGH
13 of 14
FIGURE 13 FT‐IR spectrum for the
DBT before and after desulfurization
process
TABLE 8 The smaller of U test values for S‐PAC
be reused for at least five cycles without a consequential
decrease in the catalytic activity in the oxidative desulfur-
ization of SCs.
The smaller of U test values
Critical
n2/n2
values of U
DBT &BT
BT & Th
DBT & Th
7*7
8
20.5
20.0
20.0
ACKNOWLEDGMENTS
The authors are grateful for financial supported by the
Iran National Science Foundation: INSF 97000426. Also,
the First author of this paper gratefully acknowledges
the support from department of Food Science and Agri-
cultural Chemistry, Macdonald Campus, McGill Univer-
sity and special thanks Dr. Ashraf Ismail for providing
research facilities.
TABLE 9 The obtained Kruskal‐Wallis of S‐PAC
Calculated
values of
Chi‐
square
Critical
values of
Chi‐
p
df Α
square
Th BT DBT Th
BT
DBT
2
0.100 4.61
5.00 4.76 4.74 p < 0.1 p < 0.1 p < 0.1
ORCID
Zahra Shokri Aghbolagh
https://orcid.org/0000-0002-
0255-9567
4 | CONCLUSIONS
In this study, we describe the activation behavior of a
TBAPW11Zn@TiO2@PAni nanocomposite for the oxida-
tive desulfurization of SCs from simulated and real gaso-
line. The SCs is oxidized mainly to water‐soluble polar
compounds, such as sulfoxide and sulfone, which are in
situ extracted into the water catalyst phase. The
TBAPW11Zn@TiO2@PAni hybrid demonstrated excellent
catalytic activity and selectivity in the ECODS system.
Moreover, we could display that the nanocomposite can
REFERENCES
[1] B. Bertleff, J. Claußnitzer, W. Korth, P. Wasserscheid, A. Jess, J.
Albert, ACS Sustainable Chem. Eng. 2017, 5, 4110.
[2] S. Iwao, Y. Baba, Carbon 2016, 98, 115.
[3] B. Bertleff, R. Goebel, J. Claußnitzer, W. Korth, M.
Skiborowski, P. Wasserscheid, A. Jess, J. Albert, ChemCatChem
2018, (20), 4602.
[4] H. Zhang, J. Gao, H. Meng, C. X. Li, Ind. Eng. Chem. Res. 2019,
19, 6658.

14 of 14
KHORRAMI AND AGHBOLAGH
[5] W. Jiang, L. Dong, H. Li, H. Jia, L. Zhu, W. Zhu, H. Li, J. Mol.
Liq. 2019, 274.
[27] J. S. Beck, J. C. Vartuli, W. Jelal Roth, M. E. Leonowicz, C. T.
Kresge, K. D. Schmitt, C. T. W. Chu, et al., J. Am. Chem. Soc.
1992, (27), 10834.
[6] S. Otsuki, T. Nonaka, N. Takashima, W. Qian, A. Ishihara, T.
Imai, T. Kabe, Energy Fuels 2000, (6), 1232.
[28] J. A. F. Gamelas, A. M. V. Cavaleiro, E. de Matos Gomes, M.
Belsley, E. Herdtweck, Polyhedron 2002, (25), 2537.
[7] M. A. Rezvani, Z. Shokri Aghbolagh, H. Hosseini Monfared, S.
Khandan, J. Ind. Eng. Chem. 2017, 52, 42.
[29] Z. Nadealian, V. Mirkhani, B. Yadollahi, M. Moghadam, S.
Tangestaninejad, I. Mohammadpoor‐Baltork, J. Coord. Chem.
2013, (7), 1264.
[8] J. Tong, W. Wang, L. Su, Q. Li, F. Liu, W. Ma, Z. Lei, L. Bo,
Catal. Sci. Technol. 2017, 1, 222.
[30] H. Yang, T. Song, L. Liu, A. Devadoss, F. Xia, H. Han, H. Park,
W. Sigmund, K. Kwon, U. Paik, J. Phys. Chem. C 2013, (34),
17376.
[9] J. J. Walsh, A. M. Bond, R. J. Forster, T. E. Keyes, Coord. Chem.
Rev. 2016, 306, 217.
[10] W. Jiang, H. Jia, H. Li, L. Zhu, R. Tao, W. Zhu, H. Li, S. Dai,
[31] S. Wang, Z. Tan, Y. Li, L. Sun, T. Zhang, Thermochim. Acta
2006, 2, 191.
Green Chem. 2019, 21, 3074.
[11] G. Wang, D. Wang, X. Xu, L. Liu, F. Yang, J. Hazard. Mater.
2012, 217, 366.
[32] A. Olad, S. Behboudi, A. Akbar Entezami, Bull. Mater. Sci.
2012, (5), 801.
[12] F. Banisharif, M. R. Dehghani, J. M. Campos‐Martin, Energy
Fuels 2017, 5, 5419.
[33] C. Lai, H. Z. Zhang, G. R. Li, X. P. Gao, J. Power Sources 2011,
10, 4735.
[13] M. Chamack, A. R. Mahjoub, H. Aghayan, Chem. Eng. J. 2014,
255, 686.
[34] H. Xia, Q. Wang, Chem. Mater. 2002, 5, 2158.
[35] P. Rajakani, C. Vedhi, Int. J. Ind. Chem. 2015, 4, 247.
[14] X. Liao, D. Wu, B. Geng, S. Lu, Y. Yao, RSC Adv. 2017, (76), 48454.
[36] A. S. Danial, M. M. Saleh, S. A. Salih, M. I. Awad, Power
Sources. 2015, 293, 101.
[15] M. A. Rezvani, A. Fallah Shojaie, M. H. Loghmani, Catal.
Commun. 2012, 25, 36.
[37] M. A. Rezvani, Z. Shokri Aghbolagh, H. Hosseini Monfared,
[16] H. Shi, M. Ruth, C. Vincent a, Z. Jinshun, Part. Fibre. Toxicol.
2013, 10, 15.
Appl. Organomet. Chem. 2018, (12), e4592.
[38] A. F. Shojaei, M. A. Rezvani, M. H. Loghmani, Fuel Process.
Technol. 2014, 118, 1.
[17] L. Ni, G. Yang, C. Sun, G. Niu, Z. Wu, C. Chen, X. Gong, C.
Zhou, G. Zhao, J. Gu, W. Ji, Mater. Today Energy 2017, 6, 53.
[39] L. Hao, M. Wang, W. Shan, C. Deng, W. Ren, Z. Shi, H. Lü,
[18] B. K. Kuila, B. Nandan, M. Böhme, A. Janke, M. Stamm, Chem.
Commun. 2009, (38), 5749.
J. Hazard. Mater. 2017, 339, 216.
[40] M. A. Rezvani, M. Shaterian, F. Akbarzadeh, S. Khandan,
[19] K. Zhang, L. L. Zhang, X. S. Zhao, J. Wu, Chem. Mater. 2010, 4,
Chem. Eng. J. 2018, 333, 537.
1392.
[41] X. Yan, J. Yan, P. Mei, J. Lei, j. Wuhan. Univ. Technol. Mat. Sci.
Edit. 2008, 6, 834.
[20] M. A. Rezvani, M. Shaterian, Z. Shokri Aghbolagh, R. Babaei,
Environ. Prog. Sustainable Energy 2018, (6), 1891.
[21] M. A. Rezvani, O. Feghhe Miri, Chem. Eng. J. 2019, 369, 775.
[22] J. Zongxuan, L. Hongyinga, Z. Yongna, L. Can, Chin. J. Catal.
2011, 32, 707.
How to cite this article: Khanmohammadi
Khorrami MR, Shokri Aghbolagh Z. Synthesis and
non‐parametric evaluation studies on high
performance of catalytic oxidation‐extraction
desulfurization of gasoline using the novel
TBAPW11Zn@TiO2@PAni nanocomposite. Appl
Organometal Chem. 2019;e5299. https://doi.org/
10.1002/aoc.5299
[23] M. A. Rezvani, M. Alinia Asli, S. Khandan, H. Mousavi, Z.
Shokri Aghbolagh, Chem. Eng. J. 2017, 312, 243.
[24] R. Hajian, F. Jafari, J. Iran. Chem. Soc. 2018, 1, 1.
[25] D. Julião, A. C. Gomes, M. Pillinger, L. Cunha‐Silva, B. de Castro,
I. S. Gonçalves, S. S. Balula, Fuel Process. Technol. 2015, 131, 78.
[26] O. A. Kholdeeva, M. P. Vanina, M. N. Timofeeva, R. I.
Maksimovskaya, T. A. Trubitsina, M. S. Melgunov, E. B.
Burgina, J. Mrowiec‐Bialon, A. B. Jarzebski, C. L. Hill,
J. Catal. 2004, 2, 363.