PREPARATION OF V2O5 @MESOPOROUS SILICA
SPHERE FOR NOVEL DUAL OXIDATIVEADSORPTIVE
DESULFURIZATION
Shorouk Shawky*1 ; Nasser H. Shalaby1 ; Dalia R. Abd El-Hafiz1 ;
S. Said1 ; Maher Helmy Helal2 and Sahar K. Mohamed2
1 Catalysis lab., Refining department, Egyptian Petroleum Research Institute, Nasr City,
Cairo 11727, Egypt
2Chemistry Department, Faculty of Science, Helwan University, Ain Helwan, Cairo,
11795, Egypt
Key Words: Oxidative-Adsorptive desulfurization; Mesoporous silica
spheres; micelle-template; Vandia.
ABSTRACT:
V2O5 nanoparticles were supported on mesoporous silica spheres
(V2O5/MSS) by impregnation technique. Where mesoporous silica sphere
(MSS) was synthesized via micelle-template method. The structure and
morphology were tested using XRD, FTIR, BET surface area, TEM, and DLS
techniques. The results demonstrated that the samples were amorphous with a
mesoporous structure, special interior spaces, and high specific surface area.
The prepared sample was tested for duel oxidative/adsorptive performance of
model diesel fuel. The desulfurization process was tested in the presence of
H2O2 as an oxidizing agent at different reaction conditions (temperature, contact
time, and initial concentration) using a batch system by either stirring or
ultrasonic. The data indicate that V2O5/MSS shows good performance toward
duel oxidative/adsorptive desulfurization with 100% removal efficiency under
sonication within 1.5h but in stirring within 2h at 60oC using 600 ppm initial
concentration.
1. INTRODUCTION
Mesoporous materials represent a range of porous materials with 2–50
nm diameters. They are commonly used in numerous fields, catalysis,
biomedicine, and sensor. Because of their incredible properties and
characteristics, including ultra-high surface areas, controllable pore sizes, and
large volumes of pores (1). Various techniques such as Sol-Gel processing(2),
Template assisted techniques(3), Microwave-assisted techniques(4), Chemical
etching techniques can be used to synthesize mesoporous materials(5).
Mesoporous silica are considered a good selection because of their amorphous
character and the easy process of sphere formation (6–11).
Moreover, it is known that the earth's crust is rich in the element of
vanadium (V), and the vanadium oxides have different forms of crystalline and
*Corresponding author: Shorouk Shawky1
Email: Shorouk.shawky92@gmail.com
Fax: +20 222747433
Egypt. J. of Appl. Sci., 35 (9) 2020 126-145
multi-oxidation state (II – V). Vanadium oxides exhibit significant interactions
with molecular or ionic species, higher catalytic efficiency and/or effective
correlations between electron and electron (12). From the practical and
economical points of view, V2O5 has a greater potential to be applied as catalyst
active phase for oxidative desulfurization (ODS) process (13). Due to their large
pore size with controlled distribution, which may be beneficial in allowing
accessibility of large molecular size sulfones to the surface active sites, much
attention was paid to development of mesoporous oxide-based materials (14).
On the other hand, the worldwide attention has been drawn to the sulfur content
of diesel fuel as after combustion, the sulfur compounds in the fuel are
converted to sulfur oxides (SOx), which cause acid rain and air pollution, as
well as catalyst toxicity. Governments worldwide have noticed these concerns
and have imposed new strict environmental regulations on fuel sulfur levels to
minimize SOx emissions (15,16). Several approaches have been investigated to
remove those heterocyclic sulfur compounds (14,17–22). The traditional fuel
sulfur removal method is called hydrodesulfurization (HDS), a well-known
catalytic process in the refining industry. However, HDS is not efficient in
removing heterocyclic sulfur compounds such as dibenzothiophene (DBT) and
its derivatives. It is also demands strict operating conditions such as high
temperatures, high pressure, and high consumption of hydrogen(23). Oxidative
desulfurization (ODS) is a great alternative approach to hydrodesulfurization.
This eliminates the use of costly hydrogen and can be performed under mild
conditions with short time of reaction, greater selectivity and efficiency (24,25).
In the ODS process, these refractory aromatic organosulfur compounds (such as
DBT and its derivatives) are quickly oxidized into their corresponding
sulfoxides and highly polar sulfones, which can be removed from the fuel by
adsorption or extraction (26). Since heterocyclic sulfur compounds are
relatively large molecules, the pore diameter and surface area of the
catalyst have to be taken as part of the catalyst design(13). Adsorption
desulfurization technology is considered promising alternative method for deep
desulfurization, owing to the potential benefits of low capital, the mild operating
conditions of temperature and pressure, low environmental impact and greater
reaction specificities, and availability of adsorbents with high adsorption
capacity (24). The combination of oxidation and adsorption is better than direct
adsorption to achieve a better desulfurization performance (27). However, there
are few studies reported that consider insitu oxidative-adsorptive desulfurization
as a more efficient than either oxidation or adsorption (28–30). In this case, the
desulfurization efficiency is generally based on the catalyst/adsorbent system
characteristics (31,32).
According to the previous statement, our aim to prepare ordered
mesoporous materials with narrow pore size distribution for removal of sulfur
compounds from model diesel fuel. Firstly, the mesoporous silica spheres
(MSS) will synthesized via micelle-template method then will impregnated with
127 Egypt. J. of Appl. Sci., 35 (9) 2020
V2O5 using a wet impregnation technique to deposit V2O5 on mesoporous silica
spheres. The prepared catalyst will be characterized by XRD, FTIR, BET, TEM
and DLS techniques. The efficiency of the prepared sample as a catalystadsorbent
system will be examine for oxidative-adsorptive desulfurization of
dibenzothiophene (DBT), as a model diesel oil of sulfur-containing compound,
in presence of H2O2 as oxidant. To achieve the best selectivity and activity,
different factors were studied such as contact time, reaction temperature, and
initial concentration of DBT. Additionally, the effect of ultra-sonication versus
stirring will be also studied.
2. EXPERIMENTAL:
2.1. Materials:
Tetraethoxysilane (TEOS, 99.9%, Sigma Aldrich), Aqueous
ammonia solution (25–28 wt.%, Merck), Ammonium metavanadate
(NH4VO3, 99.8%, Sigma Aldrich), Cetyltrimethylammonium bromide
(CTAB, Sigma Aldrich), Ethanol ( EtOH (99 %, Merck Chemicals), Oxalic
acid (99.5%, Merck), Dibenzo-thiophene (99 %, Merck), Hydrogen peroxide
(aqueous solution, 30%), Hexane and Deionized water.
2.1.1. Synthesis of mesoporous silica spheres (MSS):
Mesoporous silica sphere (MSS) was prepared via the hydrolysis
and condensation of TEOS in an aqueous basic-ethanol medium. Typically,
0.16g of CTAB was dissolved in100 mL of mixed aqueous solution of
ethanol and water with continuous stirring. Then 1.0 mL of TEOS and 1.0
mL of ammonia were added sequentially. The resulting mixture was further
stirred for 6 h at 30 °C until it gives a white suspension. After reaction, the
suspension was centrifuged and washed with water and ethanol by two
cycles to remove any residual organics and ammonia. The final particles
were collected after drying over-night at 80 °C then calcined at 500 °C for 5
h in static air (heating rate 2 °C min-1).
2.1.1. Synthesis of V2O5/mesoporous silica spheres:
To prepare V2O5/MSS, the dried sample of mesoporous silica sphere
(MSS) was impregnated with an aqueous solution of NH4VO3 that dissolved
in oxalic acid solution and stirred at ambient temperature for 10 h, The
obtained sample was first dried for 24 h at 120 °C and then calcined for 5 h
at 550 °C in static air (heating rate 2 °C min-1).
2.3. Characterization of the prepared sample:
X-ray diffractometer (XRD) (X'Pert PRO, Analytical, Netherlands)
tested the crystal structure of the prepared samples using CuKp radiation at
40 kV, 2θ = 0.02 ° phase size and 0.4 sec step time of scanning. N2
adsorption-desorption isotherms (BET) estimated at liquid N2 (-196 ° C) by
using a NOVA2000 gas sorption analyzer (Quanta Chrome Corporation)
device was examined the texture properties. Fourier-transform infrared
Egypt. J. of Appl. Sci., 35 (9) 2020 128
spectroscopy (FT-IR) spectrum was reported between 500 and 4000 cm-1
with Perkin Elmer FTIR spectrometer (model one FT-IR spectrometer,
USA). High-resolution transmission electron microscopy (HRTEM) was
conducted by using a JEOL 2100F TEM at 200 kV of the accelerating
voltage. To prepare TEM sample, A dilute colloidal sample mixture was
ultra-sonicated in ethanol for 30 minutes and a drop of this solution was
placed on a carbon-coated Cu TEM grid. The average particle size
distribution of prepared samples was obtained by Dynamic light scattering
(DLS). Analysis was carried out using measurements at 25 °C using a
Zetasizer NanoZS (Malvern Instruments Ltd., UK).
2.4. Activity test:
The duel oxidation-adsorption efficiency of the V2O5/MSS was
examined for DBT removal from liquid fuels. In a standard experiment, a
condenser, a thermometer, a magnetic bar and a hot plate were fitted with a
25 ml three-necked flask. In this flask, 0.02 g V2O5 / MSS and 0.4 ml H2O2
are applied to a definite concentration of 10 ml of DBT solution (in hexane
as a solvent).
Different parameters that influence the efficiency of DBT removal
have been investigated, such as the absence of adsorbent or an oxidizing
agent, contact time (up to 300 minutes), reaction temperature (30-80oC) and
initial DBT concentration (200-1000 mg L-1). Also, the effect of stirring
versus ultra-sonication on the removal efficiency was investigated. GC-FPD
has been used to detect the concentration of residual DBT. The efficiency of
DBT removal (%E) and the adsorption capacity qe (mg g-1) were determined
as follows:
% *100
o
o e
C
C C
E
(1)
m
o e
V
q C C e
(2)
Where Co is the initial DBT concentration of its solution and Ce are
remaining concentration of DBT after the adsorption (mg L-1). V is the
DBT volume in the solution, and m is the mass of the V2O5/MSS (g).
3. RESULTS AND DISCUSSION
3-1Characterization of the Prepared Samples:
XRD pattern of the prepared V2O5/MSS after thermal treatment at 550°C
in air is shown in Fig. 1. showed a broad diffraction peak in the region of
2Ѳ 20-38° indicating that the silica samples are of amorphous structure
matrix (1,33). Despite the amount of V2O5, some low-intensity
diffraction peaks related to the V2O5 supported on the amorphous silica
pattern are observed (34).
129 Egypt. J. of Appl. Sci., 35 (9) 2020
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90
Intensity(a.u)
2-Theta(degrees)
V2O5
Fig. 1. XRD pattern of the prepared V2O5/MSS
Fig. 2. showed the FT-IR spectrum of the obtained samples at
different preparation steps, dried core-shell solid silica spheres (SSCS),
Mesoporous silica sphere (MSS) and V2O5/MSS. A distinctive Si-OH
stretching vibration was displayed at about 3423 cm−1.The structural
differences between obtained (SSCS) and (MSS) were observed through
the transverse optical mode of Si—O—Si asymmetric stretching
vibration band exhibits a distinct red shift from 1101 to 1086 cm-1 of
(MSS). The redshift of the Si—O—Si band suggests a more open
structure in (MSS), which demonstrates the higher degree of
condensation of silicate species (35). Also, The peaks at 2925 cm−1 and
2854 cm−1 were attributed to asymmetrical stretching vibration of -CH3
and -CH2-, which caused by organic matter inside the dried core-shell
silica sample (SSCS) (36).The strong absorption peak at 1082 cm−1 was
belonged to Si-O-Si asymmetric stretching(35). The peaks at 801 cm−1
and 464 cm−1 were assigned to symmetric stretching vibration of Si-O,
and the peak at 964 cm−1 was due to bending vibration absorption of Si-
OH. Peak around 1635 cm−1 was the bending vibration peak of H-O-H in
water (36). The structural differences between obtained (MSS) and
V2O5/MSS were observed where V2O5/MSS spectrum shows that the
transverse. The peaks at 939, 804 and 469 cm-1 belong to stretching
vibration of terminal oxygen bonds of Si-O-V vibrations (37), the
vibration of doubly coordinated oxygen (bridge oxygen) bonds, and the
asymmetric and symmetric stretching vibration of triply coordinated
oxygen (chain oxygen) bonds, respectively (38).
Egypt. J. of Appl. Sci., 35 (9) 2020 130
0
50
100
150
200
250
3900 3400 2900 2400 1900 1400 900 400
Transmittance ( % )
Wavenumber ( cm-1 )
MesopCorhouas rsitli cTa istplheere (MSS)
V2O5/MSS
Dried core shell solid silica spheres(SSCS)
Fig. 2. FT-IR spectrum of the obtained samples at different
preparation steps, Dried core shell solid silica
spheres(SSCS), Mesoporous silica sphere (MSS),
V2O5/MSS
HR-TEM images show the shape of the as-prepared samples. Typical show
that as-prepared of dried core-shell solid silica spheres(SSCS) and
Mesoporous Silica Sphere (MSS) after calcination are of spherical
morphology (Fig. 3a, b), and SSCS exhibit a smooth surface while MSS
show rough pore-like channels indicating the presence of micelle aggregates
(35). The average radius of the spheres was not affected by calcination
processes (PSD ~ 100 nm), as confirmed by DLS data (Fig. 3c).
0
5
10
15
20
25
0 50 100 150 200 250 300 350 400 450
Number(%)
Size(d.nm)
V2O5/MSS
MSS
SSCS
( C )
Fig . 3. HRTEM images of obtained samples at different preparation steps,
(a) TEM image of as-prepared dried core-shell solid silica spheres(SSCS). (b)
TEM of Mesoporous Silica Sphere (MSS) after calcination (c) Particle size
distribution of Silica Sphere at different preparation steps and (V2O5/MSS)
after calcination
( a ) ( b )
131 Egypt. J. of Appl. Sci., 35 (9) 2020
Textural properties of the prepared V2O5/MSS samples are illustrated in
(Fig. 4) Nitrogen adsorption-desorption shows type IV of isotherms, which
are typical of mesoporous materials. The hysteresis loop of these isotherms
can be classified as type H3, characterized by a triangular shape (39). Since
the absorption and desorption branches appear at a relatively low pressure of
about 0.4, materials with this kind of loop can be identified as materials with
relatively uniform channel like-pores (40). Likewise, the pore diameter
distribution determined with BJH method showed a broad range of pore
diameters, mostly below 4 nm for samples synthesized. In the case of
spherical, solid silica particles, specific surface areas as high as 403.501m²/g
correspond to diameters of 3.33 nm and total pore volume 0.5436 cm3g-1
which indicates the high porosity of the prepared sample (1,41)
0
50
100
150
200
250
0 0.5 1
Adsorbed Quantity (cm3g-1)
P/P0
( a )
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 20 40 60 80 100 120 140
Adsorption (cm3/nm/g)
Pore diameter (nm)
( b )
Fig. 4. N2 adsorption-desorption isotherms (a), the corresponding pore
size distribution plots obtained by BJH method (b)
3.2. Oxidative/Adsorptive Desulfurization Process
The duel oxidative/adsorptive desulfurization of DBT was tested by
using the prepared catalyst V2O5/MSS. The desulfurization process was
carried by using either stirring system or ultrasonicator as batch reaction
systems in presence of an oxidizing agent as H2O2. The model diesel fuel
was prepared by dissolving DBT in n-hexane. Moreover, the duel oxidationadsorption
experiments were performed by changing temperature (30-70oC),
initial concentration of DBT (200-1000 ppm) and the time from 10 to 300
min. To prove the coupling of catalytic oxidation and the adsorption process
of prepared catalyst, the experiment was alternately carried out in the
absence and presence of the V2O5/MSS or H2O. First of all, the
desulfurization process was carried on 600 ppm of DBT for 60 min under
stirring system at 60oC, in the absence and presence of 0.02 g V2O5/MSS
and/or 0.4 ml of H2O2. The removal efficiency (%E) was detected and
presented in (Table. 1). From the obtained result, It is obvious that Using
V2O5/MSS without the oxidizing agent showed low removal efficiency (%E)
which prove the low adsorptive ability of V2O5/MSS toward DBT.
However, using of H2O2 in absence of V2O5/MSS results in poor removal
Egypt. J. of Appl. Sci., 35 (9) 2020 132
(%E), which indicates the slow rate of DBT oxidation. Using both
V2O5/MSS and H2O2 enhances significantly the removal (%E) which
indicates the duel oxidative adsorption property of the prepared catalyst.
Table 1. Removal (%E) of DBT in presence and absence of V2O5/MSS
Experiment no. V2O5/MSS (g) H2O2 (ml) (%E)
60 oC
1 0.02 - 39.34
2 - 0.4 27.61
3 0.02 0.4 71.5
This data indicates the oxidative ability of the prepared catalyst
V2O5/MSS of DBT by H2O2 producing sulfones and/or sulfoxides forms
(scheme. 1). In consequence, The adsorption capacity increases due to
the greater adsorptive affinity toward sulfoxides and sulfones (polar
O=S=O) than nonpolar thiophenic compounds (42,43).
Scheme. 1. Catalytic Oxidative desulfurization of DBT to DBT sulfone
3.2.2. Effect of contact time
In order to find a suitable equilibrium contact time, this test was
carried out at time intervals ranging from 10 to 300 min. the removal
(%E) of model diesel of DBT using oxidative/adsorptive system as a
function of interval contact time at 60 °C shown by Fig. 5 comparing
both stirring and sonication techniques. At either stirring or sonication,
the removal (%E) increases by increasing the reaction time till
equilibrium that’s due to the availability of vacant active sites on
V2O5/MSS surface. then the oxidative desulfurization process to
sulphone slows down due to occupying the active sites. Hence, In the
case of stirring, 120 min was selected for further experiments.
Comparing these results with the previous work indicates that,
V2O5/MSS duel system achieved to equilibrium faster than those based
only on adsorption (44,45), but the desulfurization process attained
equilibrium 90 min in the case of sonication. This can be recognized by
the specific effect of ultrasound waves, where micro-streaming bubbles
are produced by the acoustic cavitation of the ultrasonic technique, which
improves mass transfer in the reaction mixture (46,47).
133 Egypt. J. of Appl. Sci., 35 (9) 2020
0
10
20
30
40
50
60
70
80
90
100
0 50 100 150 200 250 300
Removal(%E)
Time(min)
stirring
Sonication
Fig. 5. Effect of contact time (% E) under stirring or sonication on 0.02
g of adsorbent, 10 ml of 600 ppm DBT solution for 300 min
Adsorption kinetics study
Kinetics of The experimental results have been studied by applying the
well-known pseudo–first–order and pseudo–second–order models
(48,49). Their expressions of mathematics are given in Eqs. ( 3 – 5 ).
The pseudo-first–order model is written as follows:
ln (qe − qt) = ln qe – k1t (3)
The pseudo second order equation is stated as follows:
t q
t
=
1
2
2 e k q
+
e q
t
(4)
i R = 2
2 e k q (5)
where qe and qt are the adsorbed amounts at equilibrium (mg g–1) and time t
respectively while k1 (min–1) is the rate constant of pseudo first-order
adsorption that calculated from linear plot of Log (qe − qt) versus time. k2
(g.mg–1 min–1) is the rate constant of pseudo second order adsorption which
can calculated by Plotting a straight line from t/qt verses t. the value of the
correlation coefficient ( R2 ) was used to choose the best-fit model. Table. 2
and (Fig. 6) showed a better fitting to pseudo– first–order model with R2 ≈1
under sonication or stirring. Also, it shows the comparable theoretical values
qe with to the experimental values.
Table. 2. Detected kinetics parameters for duel oxidative adsorption
of DBT (600 mg/l); 021 min at 60°C
Conditions experimental qe
(mg/g)
pseudo- first order pseudo- second order
qe
(mg/g)
K1 X103
(min-1)
R2 qe(mg/g) K2 X 103
(g.mg-1.min-1)
R2
Stirring 299.288
317.770
0.008
0.970 -78.457 0.14 0.573
Sonication 299.585
309.318
0.019
0.912 404.172 0.037 0.701
Egypt. J. of Appl. Sci., 35 (9) 2020 134
y = -0.0085x + 5.7613
R² = 0.9672
y = -0.0191x + 5.7344
R² = 0.9123
3
4
4
5
5
6
6
0 10 20 30 40 50 60 70
ln(qe-qt)
t,min
Linear (stirring) Linear (sonication)
( a )
y = -0.0127x + 1.1598
R² = 0.5727
y = 0.0016x + 0.1896
R² = 0.763
0
0
0
1
1
1
1
1
0 10 20 30 40 50 60 70
t/qt
t, min
( b )
Fig. 6. Models of Kinetic for the adsorption process (a) pseudo firstorder
kinetic model, (b) pseudo-second-order model.
3.2.3. Effect of initial concentration
To find the maximum capacity of V2O5/MSS as adsorbent, five
samples of DBT solution with different concentrations of 200, 400,
600,800, and 1000 ppm were used. This parameter was carried by using
0.02g of V2O5/MSS duel system for 120 min at 60oC under stirring. As
shown fig. 7 the amounts adsorbed (mg g–1) increases with increasing of
initial concentration that’s due to improve the mass transfer of adsorbate
species from the bulk solution to the absorbent surface (44,45,50).
Additionally, the sample did not achieve saturation up to initial
concentration of 1000 mg L-1.
0
50
100
150
200
250
300
350
400
450
0 200 400 600 800 1000 1200
qe( mg g-1 )
Intial Concentration( mgL-1 )
Fig. 7. Adsorption capacity as function of DBT initial concentration
at 60℃ under stirring on 0.02 g of adsorbent, 10 ml of 600 ppm
DBT solution for 120 min
3.4. Adsorption isotherm
Models of adsorption isotherms were also used to study the Adsorption
process at equilibrium as a function of initial DBT concentration. Two
models Langmuir and Freundlich.
The Langmuir isotherm (51) can be expressed mathematically as the
following Eq (6).
135 Egypt. J. of Appl. Sci., 35 (9) 2020
e
e
q
C
=
e bQ
1
+
e
e
Q
C
(6)
Where Ce is the equilibrium concentration of DBT in solution
(mg/L), is the maximum theoretical capacity at the monolayer (mg/g)
and b is the constant of Langmuir (l/mg).
The Freundlich isotherm (52)can be expressed mathematically as the
following Eq (7).
(7)
where qe (mg/g) is the DBT amount adsorbed at
equilibrium, Ce (mg/L) is the remaining concentration of DBT in model
oil, KF the Freundlich constant [mg/g (mg/l)n] represents adsorption
capacity and n is adsorption favorability constant which they are
calculated from slope and intercepts of linear plot of ln qe against ln Ce.
The value of 1 / n is being closer to 0, which implies that the adsorbent
surface is more heterogeneous and promotes the multilayer adsorption
process.
Table. 3.and (Fig. 8) showed the calculated values of models. The model
of Langmuir isotherm has a good fittings of the experimental data with
R2 = 0.909 which suggests a monolayer adsorption process on the
homogeneous surface of the adsorbent.
Table. 3. Obtained data from fitting experimental results with the
three models:
Langmuir
b(L mg-1) 0.031556578
qmax(mg g-1)
450.6500415
R2
0.909470584
Freundlich
Kf ((mg/g)/(mg/L)n)
177.4819303
1/n
0.08724925
R2
0.078955289
y = 0.0872x + 2.2492
R² = 0.079
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5
log Qe
log Ce
y = 0.0022x + 0.0703
R² = 0.9095
0
0.1
0.2
0.3
0.4
0.5
0.6
0 50 100 150 200 250
Ce/qe
Ce
( b )
( a )
Fig. 8. The duel oxidative adsorption models for DBT removal : (a)
Langmuir isotherm, and (b) Freundlich isotherm.
Egypt. J. of Appl. Sci., 35 (9) 2020 136
3.5. Adsorption mechanism
It is known that the adsorption mechanism follows a complex pathway
and is followed by both the surface and the diffusion of the pore but in
different areas. The intra_particle diffusion model was evaluated
according to ―Weber and Morris equation‖ to investigate the diffusion
process (53,54).
The initial rate of intra-particle diffusion in this model can be expressed
mathematically as the following equation:
qt = ki t 1/2 + C (8)
where ki is the constant of the intra_particle diffusion rate (mg/g.min0.5),
and C (mg/g) is a constant attributed to the boundary layer effect and
obtained from the intercept value by plotting qt versus (t0.5). In this
equation, the C value give a picture about the rate-determining step
where, C= 0, intraparticle diffusion is the only rate-determining step and
C≠ 0, the process was controlled by a variety of mechanism
As shown in (Fig. 9), the multilinear relationship with C > 0,
indicate that, more than one step occurred during the desulfurization
process over the prepared catalyst adsorbent (V2O5@MSS) system under
both stirring and ultrasonication. This implies that adsorption takes place
in three stages; the early stage is the rapid adsorption of the surface,
followed by the slower stage of intra-particle diffusion and finally the
equilibrium stage (46,47).
0
25
50
75
100
125
150
175
200
225
250
275
300
325
0 2 4 6 8 10 12 14 16
qt
t0.5(min0.5)
Intraparticle diffusion model
stirring sonication
Fig. 9. Intra-particle diffusion plot for adsorption of 600 mg/l of as
initial concentration of DBT at 60oC for 120 min
137 Egypt. J. of Appl. Sci., 35 (9) 2020
3.6. Thermodynamics studies
The key factor for both catalytic and adsorptive desulfurization
reactions is temperature (55). The influence of temperature was set on
the DBT solution desulfurization process using V2O5 / MSS as a dual cat
alyst-adsorbent system has been investigated.The adsorption process was
performed at various temperatures under stirring (303, 313, 323, 333and
343 K). (Fig. 10) displays the relation between adsorption capacity (qe)
and temperature. It shows that a gradual increase in removal (percent E)
was obtained by increasing the temperature applied from 303 to 333 K
and improving the dual oxidative / adsorption process. However, a
further rise in the temperatures of reaction leads to a reduction in the
potential of adsorption. This has been shown by the decomposition of
H2O2 into water, which reduces sulfone production (43). These results
indicate that the process of desulfurization using V2O5 / MSS occurs
adequately at temperatures equal to or even lower than 333 K (56).
40
90
140
190
240
290
340
280 290 300 310 320 330 340 350
qe mg/g
Temperature (k)
Fig. 10. The adsorption capacity as a function of applied temperature
using V2O5/MSS under stirring; 600 ppm of DBT as initial
concentration at 60oC for 120 min.
The thermodynamic adsorption parameters as change of free Gibbs
energy (ΔG), change of enthalpy (ΔH) (kJ mol−1) and change of entropy
(ΔS) (J mol−1 K−1) were determined by using the results of experimental
adsorption isotherms up to 333 K. The thermodynamic adsorption
parameters(ΔH), (ΔG) and (ΔS) were calculated by using the following
equations (9-11):
Egypt. J. of Appl. Sci., 35 (9) 2020 138
d K =
e
e
C
q
(9)
RT ln Kd (10)
d ln K =
R
S
–
RT
H
(11)
where R (8.314 X10-3 kJ K−1 mol−1) is the gas constant and T is the
applied kelvin temperature (K). from (Eq. 13), ΔG was demonstrated
while from slope and intercept from the plot of ln Kd versus 1/T of (Eq.
14), (ΔH) and (ΔS) were measured. The values of ΔH and ΔS are
presented in (Table. 4) (ΔS) and (ΔH) showed positive values that
suggest that the adsorption mechanism of endothermic catalytic oxidation
contributes to a growing disorder. (ΔS) and (ΔH) show positive values
and hence the negative sign of (ΔG) indicates the spontaneity of
adsorption process (54,57,58).
It showed positive values
Table. 4. Thermodynamic parameters for duel oxidation adsorption
process of DBT (600 mgg-1) for 120 min under stirring.
T (K) ln Kd ΔG (KJ mol-1) ΔH (KJ mol-1) ΔS (J mol-1 K-1)
303 0.332362832 -0.837269169
37.57273881
130.4431184
313 0.778222795 -2.02515517
323 1.807364104 -4.853535328
333 5.347294101 -14.80431525
CONCLUSION
In conclusion, our study successfully synthesized mesoporous silica
spheres via micelle-template and V2O5 nano-particles supported on it
(V2O5/MSS) through impregnation technique. This novel catalyst proved its
effect as a novel duel oxidative/adsorptive system of model diesel fuel. The
Desulfurization process is performed in the presence a suitable oxidizing
agent (H2O2) at different conditions of temperature, contact time and initial
concentration under either stirring or ultrasonication. The novel catalyst
shows an effective removal about 100 % under sonication within 1.5h but in
stirring within 2h. The pseudo-first - order model could explain adsorption
kinetics (V2O5 / MSS) of the studied adsorbents. The experimental data
matches well with the Langmuir model of the isotherm which indicates a
monolayer adsorption process on the homogeneous surface of the adsorbent.
The determined thermodynamic parameters suggested that the endothermic
adsorption process was favorable for (V2O5 / MSS) adsorption.
Declaration of Competing Interest
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence the
work reported in this paper.
139 Egypt. J. of Appl. Sci., 35 (9) 2020
Acknowledgment
The authors acknowledge the financial support from the Academy of
Scientific Research and Technology in Egypt to the scientific research
students through the program of Next Generation Scholars. (ASRT- SNG 5-
2016).
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تحضیر خامس اکسد الفاندیم النانونی المحمل عمى کریات السمیکا المسامیة
لإ ا زلة الکبریت بطریقة الاکسدة-الامت ا ززیة الجدیدة )V2O5/MSS(
، شروق شوقى* 1، ناصر حممى شمبى 1، دالیا رضوان عبد الحافظ 1 ، سمر سعید 1
ماهر حممى هلال 2، سحر کمال محمد 2
1 معمل الحفا ا زت ، قسم التکریر، معهد بحوث البترول المصرى ، مدینة نصر، 11727 ، القاه رة
2 قسم الکیمیاء، کمیة العموم، جامعة حموان، عین حموان، حموان ، 11795 ، القاهرة ، مصر
)V2O5/MSS( تم تحضیر خامس اکسد الفاندیم النانونی المحمل عمى کریات السمیکا المسامیة
حیث تم تحضیر کریات السیمیکا المسامیة باستخدام .impregnation باستخدام تقنیة التشریب
و FTIR و XRD تم توصیف المادة المحضره باستخدام تقنیات ال .micelle-template method
أظهرت النتائج أن العینات کانت غیر متبمورة ومسامیة الشکل، وذات . DLS و TEM وBET
مساحات داخمیة خاصة، وکذالک مساحة سطح ممیزة عالیة. تم اختبار العینة المحضرة للأداء الاکسدة /
لنموذج وقود الدیزل. تم اختبار عممیة إ ا زلة الکبریت فی وجود ال oxidative/adsorptive الامت ا زز
کعامل مؤکسد تحت ظروف تفاعل مختمفة )درجة الح ا ررة ووقت التلامس والترکیز الأولی( H2O2
باستخدام نظام المفاعل الثابت عن طریق التقمیب أو فى وجود الموجات فوق الصوتیة. تشیر البیانات
یظهر أداءً جیدًا تجاه إ ا زلة الکبریت المؤکسدة / الامت ا ززیة مع کفاءة إ ا زلة بنسبة V2O5/MSS إلى أن
111 ٪ فى حالة استخدام تقنیة الموجات الصوتیة خلال 1.1 ساعة. ولکن باستخدام تقنیة التقمیب
وصمت نسبة الکفاءة الى 111 % خلال ساعتین عند 01 درجة مئویة باستخدام ترکیز أولی 011 جزء
فی الممیون .تتمثل الفائدة الاقتصادیة لهذه الد ا رسة فی إ ا زلة الکبریت بکفاءة من خلال اقت ا رن الأکسدة
فی ظروف درجة الح ا ررة العادیة دون الحاجة إلى مواد ماصة DBT والامت ا زز ل ثنائی بنزوثیوفین
إضافیة أو استخدام تقنیات الاستخ ا رج.
145 Egypt. J. of Appl. Sci., 35 (9) 2020
