Preparation of 4A-zeolite-based Ag nanoparticle composite catalyst and research of the catalytic properties

Article abstract of DOI:10.1039/c4ra14783a

A 4A-zeolite-based silver nanoparticle (Ag NPs) composite catalyst was prepared and its catalytic properties were studied. A hydrothermal method was used to synthesis 4A-zeolite from coal gangue raw material. Ag NPs were prepared by an in situ reduction m

Full text of DOI:10.1039/c4ra14783a

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: X. hu, J. bai, J.
wang, C. li and W. xu, RSC Adv., 2014, DOI: 10.1039/C4RA14783A.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
Preparation of 4A-zeolite base Ag nanoparticles composite catalyst and research
of the catalytic properties
Xiaosong Hu, Jie Bai*, Junzhong Wang, Chunping Li, Wei Xu
Chemical Engineering College, Inner Mongolia University of Technology, Huhhote,
0
10051, People’s Republic of China
*
Corresponding authors: Jie Bai
Tel: +86471 6575722.
Fax: +86471 6575722.
Eꢀmail address: baijie@imut.edu.cn
1

RSC Advances
Page 2 of 31
View Article Online
DOI: 10.1039/C4RA14783A
Abstract:
4
Aꢀzeolite base silver nanoparticles (Ag NPs) composite catalyst was
prepared and the catalytic properties were researched. The coal gangue as raw
materials, hydrothermal method was used to synthesis 4Aꢀzeolite. Ag NPs were
prepared by situ reduction method. The 4Aꢀzeolite base Ag NPs composite catalyst
was prepared by impregnation method. The catalyst was analyzed by a series of
characterization techniques such as scanning electron microscopy (SEM),
transmission electron microscopy (TEM), UVꢀVisible spectroscopy (UVꢀVis), Xꢀray
diffraction (XRD), Xꢀray photoelectron spectroscopy (XPS), etc. The characterization
results indicated that the Ag NPs were uniformly distributed on the 4Aꢀzeolite. Then,
the catalyst was used to catalyze the epoxidation of styrene. The oxidant was
tertꢀbutyl hydroperoxide (TBHP), and Isopropanol was used as the solvent. The good
catalytic properties of the composite catalyst were showed to us. The results showed
very high conversion of styrene (72.1%) and excellent styrene oxide (SO) selectivity
(59.5%). What’s more, the joint selectivity of SO and benzaldehyde (BZ) reached
9
3.3%.
Keywords: 4Aꢀzeolite; Ag Nanoparticles; Composite catalyst; Styrene; Epoxidation
2

Page 3 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
1
. Introduction
Aꢀzeolite has a good adsorption performance and ion exchange properties
it is widely used in petrochemical industry and environmental protection and other
[1ꢀ3]
4
,
[4]
fields in recent years .
Silver catalyst showed a good catalytic activity on the oxidation reaction, and its
largeꢀscale application is limited because the price of silver is more expensive. The
development of nanotechnology makes its application possible. Physical properties
and chemical properties of nanoꢀsilver are relatively stable, and the electronic and
catalytic performance of nanoꢀsilver is very excellent. The application prospect is
[5ꢀ7]
broad in the battery electrode material, catalyst materials, medical materials, etc
.
Preparation methods of nanoꢀsilver have both physical method and chemical
[8−11]
method. Physical methods mainly include method of laser ablation of metal
and
[12, 13]
metal vapor deposition method
. Chemical methods include gas phase reduction
[14ꢀ17]
method, liquid phase reduction method and solid phase reduction method
.
Liquid phase reduction method has been widely applied because of its low cost,
simple operation, and low requirements for equipment. The size and shape of the
nanoparticles as well as the morphology of particles aggregation were effectively
controlled by controlling the proportion of reducing agent and protective agent.
It will improve the specific surface area of nanoparticles and its catalytic
performance that nanoꢀsilver is loaded to the 4Aꢀzeolite, and it can be used to catalyze
[18ꢀ20]
oxidation reaction as a high efficient catalyst
. In addition, the combination of the
two substances promotes the recycling of catalyst, and the preparation cost of catalyst
3

RSC Advances
Page 4 of 31
View Article Online
DOI: 10.1039/C4RA14783A
will decrease, too.
Epoxides are important intermediates for the manufacture of a range of modern
commercial products such as epoxy resins, textiles, surface coatings, and biological
[21]
chemicals
. Styrene oxide and benzaldehyde are the important intermediate of
medicine and spice. In addition, benzaldehyde is the important chemical raw materials.
In recent years, more and more researchers pay their attention to styrene epoxidation
[
22ꢀ27]
.
First of all, coal gangue synthesis of 4Aꢀzeolite was used, and Ag NPs were
prepared by using in situ reduction method in this experiment. Then, the two
substances were mixed and nanoꢀsilver would be loaded to the 4Aꢀzeolite. The
4
Aꢀzeolite base Ag NPs composite catalyst was used to catalyze epoxidation reaction
[28ꢀ32]
of styrene (Fig. 1), benzaldehyde, styrene oxide, and others were obtained
.
4

Page 5 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
Fig. 1 Scheme of preparing the Ag NPs/4A-zeolite composite catalyst and chemical equation
of styrene epoxidation.
2
. Experimental
2
.1.Materials
Sodium hydroxide (NaOH, AR), polyvinylpyrrolidone (PVP, Mw=10000, AR)
2 5
and absolute ethyl alcohol (C H OH, AR) were purchased from China Medicine
Group. Deionized water was prepared by our university. Silver nitrate (AgNO
3
, AR,
5

RSC Advances
Page 6 of 31
View Article Online
DOI: 10.1039/C4RA14783A
9
9.8%) was provided by Tianjin Yingda Sparseness & Noble Reagent Chemical
Factory. Styrene (C , AR, 99.0%) was purchased from Sinopharm Chemical
Reagent Co. Ltd. Isopropanol ((CH CHOH, AR, 99.5%) was purchased from
Tianjin Beichen Founder Reagent Plant. TertꢀButyl hydroperoxide ((CH ) COOH, AR,
8
H
8
3 2
)
3
3
7
0%) was purchased from Tianjin Alfa Aesar Chemical Co. Ltd. All the chemicals
were used as received without further purification.
2
.2. Preparation of 4A-zeolite
Coal gangue powder was got by coal gangue crushing and sieving through 200
mesh sieve, then the activated coal gangue powder was available by calcining the coal
gangue powder for 1 h under 720 ℃ . The activated coal gangue powder, Sodium
hydroxide and deionized water were mixed by certain proportion, and the mixture was
stirred for 1h under 25 ℃ . The mixture was transferred to the hydrothermal reaction
kettle after the stirring was over. The hydrothermal reaction kettle was put into the
vacuum drying oven, and the kettle was maintained 6.5 h under 100 ℃ . Finally, the
4
Aꢀzeolite would be got after the suction filtration and drying. The pH needed to be
controlled at 8 or so in the process of the suction filtration.
2
.3. Preparation of silver nanoparticles
First of all, a certain amount of PVP (1.3040 g) and anhydrous ethanol (25 ml)
were mixed for 12 h at 25 ℃ , and PVP would be fully dissolved in anhydrous ethanol.
Then a certain amount of silver nitrate was put into the mixed solution, and the
proportion of silver nitrate with PVP was 1:10. Mixed solution was heated for 20
minutes through the circulating water backflow under the condition of 80 ℃ . It was
6

Page 7 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
important to note the seal in the process of experiment.
2
.4. Preparation of 4A-zeolite base Ag NPs composite catalyst and Catalytic
performance
The 4Aꢀzeolite (1 g) which had been prepared was put into the solution
containing the Ag NPs. Then the solution was stirred for 24 h at room temperature,
and the 4Aꢀzeolite base Ag NPs composite catalyst would be got after the process of
suction filtration and drying. The 4Aꢀzeolite should be activated for 2 h in 400 ℃
before it was put into the solution containing the Ag NPs.
The styrene epoxidation was carried at atmospheric pressure. The reaction
mixture which contained 1 ml styrene, 5 ml TBHP, 5 ml Isopropanol and a certain
account of catalyst (0.1 gꢀ0.5 g) was put into a 25 ml round bottom flask. Then, the
reaction would take place under reflux (at 82 ℃ ) and sufficient stirring for a period of
time (12 hꢀ48 h). The composite catalyst of Ag NPs/4Aꢀzeolite was used in the
styrene epoxidation. The catalyst was separated from the reaction mixture by filtration.
The reaction products and unconverted reactants were analyzed by an Agilent (7890A)
gas chromatograph (GC) and Agilent (5975C) gas chromatography mass spectrometer
(GCꢀMS). The GC was equipped with a flame ionization detector (FID) which
contained capillary column (SEꢀ30) and N as carrier gas. By an area normalization
2
method, the conversion of styrene and the content of each component in the products
were calculated. The styrene conversion and product selectivity were calculated as
follows:
Styrene conversion (%) = [(areas of reactant converted) × 100] / [areas of reactant
7

RSC Advances
Page 8 of 31
View Article Online
DOI: 10.1039/C4RA14783A
used]
Product selectivity (%) = [(areas of product formed) × 100] / [areas of reactant
converted]
2
.5. Characterization of catalyst
The samples were investigated by a scanning electron microscope (SEM, Hitachi,
Sꢀ3400N, Japan) which was equipped with an energy dispersive spectrometer (EDS)
and transmission electron microscope (TEM, Jeol, JEMꢀ2010, Japan and Fei,
F20SꢀTWIN, Tecnai). The samples for TEM were dispersed in ethanol by ultrasonic
treatment; and a drop of the dispersion was deposited on a TEM carbonꢀcoated Cu
grid and dried at room temperature. The UV absorbance of the obtained Ag/4Aꢀzeolite
was measured by SHIMADZU, UVꢀ3600 UV–Vis recording spectrophotometer
(Japan) with a variable wavelength between 200 and 600 nm, which was applied to
detect UV absorbance of a solid sample. The UV absorbance of liquid sample was
measured by SHIMADZU, UV3150 UV–visible spectrophotometer with a variable
wavelength between 200 and 600 nm using 10 mm quartz cells. The phase and
crystalline structures of 4Aꢀzeolite and Ag NPs were characterized by an Xꢀray
diffractometer (XRD, PIGAKV, D/MAXꢀ2500/PC, Japan) over a range of 2θ angles
from 5°to 80°. The measurements of the Xꢀray photoelectron spectroscopy (XPS)
were performed by using a Thermo fisher Scientific ESCALAB 250 spectrometer.
3
3
. Results and discussions
.1.Characterization of catalysts
8

Page 9 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
3
.1.1. Scanning electron micrograph study
Fig. 2 was the SEM images of 4Aꢀzeolite (Fig. 2A) and Ag NPs/4Aꢀzeolite
composite catalyst (Fig. 2B). From the Fig. 2A, it was shown that 4Aꢀzeolite had the
cube structure and the size of 4Aꢀzeolite was different from 1ꢁm to 1.5 ꢁm. The
images indicated smooth surface and uniform diameter 4Aꢀzeolite had been prepared
successfully. In addition, the aggregation phenomenon of zeolite wasn’t seen in Fig.
2
4
A and Fig. 2B. The zeolite had explicit shape on the border. It was shown that the
Aꢀzeolite had a rather good dispersion. After compared with Fig. 2A and Fig. 2B, it
was found that the morphology of zeolite had no changed. It indicated that the
addition of Ag NPs didn’t affect the structure of 4Aꢀzeolite, which attributed to the
relatively stable of zeolite frame. Ag NPs/4Aꢀzeolite composite catalyst was
performed on EDS equipped in the SEM. The EDS analysis revealed that the obtained
Ag NPs/ 4Aꢀzeolite composite catalyst contained Si, Al, O, Na and Ag elements. It
had been shown that silver had been loaded to the zeolite through the analysis of Fig.
2
C.
C
Fig. 2 SEM images of the 4A-zeolite (A) and Ag NPs/4A-zeolite composite catalyst (B); EDS
spectra of Ag NPs/4A-zeolite composite catalyst (C).
9

RSC Advances
Page 10 of 31
View Article Online
DOI: 10.1039/C4RA14783A
3
.1.2. Powder X-ray diffraction study
The low angle powder XRD patterns of 4Aꢀzeolite (Fig. 3A) and Ag
NPs/4Aꢀzeolite composite catalyst (Fig. 3B) were showed in Fig. 3. All the absorption
peaks were detected between 5° and 80°. The absorption peaks of 4Aꢀzeolite appeared
at 2θ = 7.2°, 10.2°, 12.5°, 16.1°, 21.7°, 24.0°, 27.2°, 29.9° and 34.2° (JCPDS
3
9ꢀ0223). From Fig. 3A, it was shown that the pattern had got all the characterized
absorption peak of 4Aꢀzeolite. It was also showed that the 4Aꢀzeolite had got higher
crystallinity. After compared with Fig. 3A and Fig. 3B, the peaks were around 2θ =
3
8.1°, 44.3° and 64.5° which were assigned to the Ag (111), (200) and (220) crystal
planes, respectively. These peaks correspond to the cubic crystal structure of silver
JCPDS 04ꢀ0783). The measured spacing of crystal lattice was 0.21 nm, 0.24 nm and
.145 nm correspond to the Ag (111), (200) and (220) crystal planes, respectively. No
(
0
other characteristic peaks of impurities were observed. It indicated that the metallic
Ag was found to be the only species in the catalysts. The diffraction peaks of Ag
species were found relatively small, which indicated the high dispersion of Ag species
on the 4Aꢀzeolite. The results indicated that impregnation method could effectively
load Ag onto the 4Aꢀzeolite, and the silver crystalline phase was formed in the zeolite
framework.
1
0

Page 11 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
B
A
44.3
38.1
64.5
10
20
30
40
50
60
70
80
2-Theta(degree)
Fig. 3 XRD patterns of the 4A-zeolite (A); Ag NPs/4A-zeolite composite catalyst (B).
3
.1.3. UV-Vis spectral study
The UVꢀVis spectra of Ag NPs/4Aꢀzeolite composite catalyst (Fig. 4A) and
filtrate (Fig. 4B) (the liquid which was acquired in the process of preparing 4Aꢀzeolite
base Ag NPs composite catalyst) was showed in Fig. 4. From the Fig. 4A, it can be
seen that a broad and characteristic absorption band associated with the formation of
silver nanoparticles (Ag NPs) appeared at 383 nm, attributed to the existence of Ag
NPs. In addition, a rather good dispersion of Ag NPs which was formed on the
4
Aꢀzeolite surface was found. We attained the conclusion from the high symmetry of
peak. What’s more, the diameters of Ag NPs were relatively small. As shown in Fig.
4
4
B, obvious absorption band at 413 nm attributed to the Ag NPs. After compared Fig.
B with Fig. 4A, it was shown that the peak position moved to the long wavelength,
and the reasonable explanation was the gather of silver particles in the filtrate. It was
11

RSC Advances
Page 12 of 31
View Article Online
DOI: 10.1039/C4RA14783A
inferred from the UVꢀVis spectra that the existence of Ag NPs on the zeolite.
383nm
A
B
413nm
300
400
500
600
Wavelength(nm)
Fig. 4 Solid-UV spectra pattern of the Ag NPs/4A-zeolite composite catalyst (A) and
liquid-UV spectra pattern of the filtrate (B).
3
.1.4. Transmission electron micrograph study
The morphology and size of nanoꢀsilver were detected and analyzed by TEM.
The TEM of Ag NPs/4Aꢀzeolite composite catalyst was showed in Fig. 5. It was
obvious that the structure of 4Aꢀzeolite had no change. It was clearly observed that
there were a large number of small dark spots on the surface of zeolite, which were
the Ag NPs on the surface of 4Aꢀzeolite. The surface of the 4Aꢀzeolite was covered
with Ag NPs, and the Ag particles were distributed very uniformly. In addition, the
aggregation phenomenon of particles wasn’t seen in Fig. 5A, Fig. 5B and Fig. 5C,
because of the addition of protective agent (PVP) when the Ag NPs were prepared. In
Fig. 5D, it was the HRTEM image of the Ag NPs/4Aꢀzeolite composite catalyst. The
crystal lattice was seen clearly in the surface of the Ag NPs/4Aꢀzeolite composite
1
2

Page 13 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
catalyst, and the measured spacing was 0.21 nm, corresponding to the interplanar (200)
spacing of Ag NPs, as observed by the above XRD patterns. Thus, it could be
confirmed that the Ag NPs with an average size of about 5ꢀ10 nm were uniformly
distributed on the surface of 4Aꢀzeolite.
A
B
C
D
Fig. 5 TEM images of Ag NPs/4A-zeolite composite catalyst (A, B and C) and HRTEM image
of Ag NPs/4A-zeolite composite catalyst (D).
3
.1.5. X-ray photoelectron spectroscopy study
The characterization of XPS was performed in order to confirm the electronic
states of Ag on the catalyst. Fig. 6 was the XPS patterns for the Ag NPs/4Aꢀzeolite
composite catalyst. In Fig. 6A, it was shown that the fully scanned spectra in the range
of 0ꢀ1300 eV of Ag/4Aꢀzeolite. The C, Si, Al, O, Na and Ag were demonstrated to
exist in the Ag NPs/4Aꢀzeolite composite catalyst. The Si, Al, O and Na were the
1
3

RSC Advances
Page 14 of 31
View Article Online
DOI: 10.1039/C4RA14783A
chemical elements of 4Aꢀzeolite. In Fig. 6B, two peaks with high intensity were
observed at 368.5 eV and 374.5 eV, which were assigned to the photoelectron spectra
of Ag 3d. These peaks correspond well with Ag 3d5/2 and Ag 3d3/2 binding energies,
0
respectively. It was shown that Ag was the only state of Ag existed in the composite
0
catalyst. The conclusion was that the Ag had been loaded onto the 4Aꢀzeolite. It
0
indicated that Ag was the only active component which promoted the styrene
epoxidation on the surface of 4Aꢀzeolite.
500000
400000
300000
200000
100000
0
A
Ag(3d)
Na(1s)
Al(2p)
O(1s)
C(1s)
Si(2p)
1200
1000
800
600
400
200
0
Binding Energy (eV)
1
00000
368.5
B
8
0000
0000
0000
0000
0
374.5
6
4
2
390
385
380
375
370
365
Binding Energy (eV)
1
4

Page 15 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
Fig. 6 XPS pattern of the Ag NPs/4A-zeolite composite catalyst.
3
.2. Catalytic activity
Many solid catalysts reported in the literatures showed high product selectivity
[
22, 23, 25, 33]
with TBHP as the oxidant
. Thus, in this work, the catalytic activities of Ag
NPs/4Aꢀzeolite composite catalyst were tested in the epoxidation of styrene with
TBHP as the oxidant. In order to get the optimal reaction conditions, different
parameters such as catalyst amount and reaction time were investigated. After the
analysis of GC and GCꢀMS detection, the main products of the reaction were styrene
oxide (SO) and benzaldehyde (BZ).
The influence of catalyst amount on the catalytic performance was investigated
by varying the catalyst amount from 0.1 g to 0.5 g and the consequences were shown
in Table 1. The reaction time was 24 h and the temperature was kept in 82 ℃. From
the table, it was found that the highest conversion of styrene (55.1%) appeared when
0
.1 g catalyst was used. The conversion of styrene had no improvement with the
increase of the catalyst amount, but the selectivity of styrene oxide and benzaldehyde
increased slightly. It is worth noting that the selectivity of styrene oxide and
benzaldehyde decreased obviously under 0.5 g catalyst. The optimal catalyst amount
was 0.1 g by the comprehensive consideration. So we chose this value to continue the
examination of reaction time.
It was investigated that the reaction time effected on the catalytic performance
after added 0.1 g catalyst into the catalytic reaction, and the consequences were
1
5

RSC Advances
Page 16 of 31
View Article Online
DOI: 10.1039/C4RA14783A
showed in Table 2. The reaction temperature was kept in 82 ℃. From the table, it was
shown that the reaction time had obvious influence on the catalytic performance. The
conversion of styrene and the styrene oxide selectivity had got obvious improvement
with the increase of the reaction time. The highest selectivity of styrene oxide
appeared at 48 h. However, the conversion of styrene increased slowly while the
selectivity of styrene oxide and benzaldehyde decreased obviously from 48 h to 60 h.
It indicated that the styrene oxide and benzaldehyde started to turn into other
byꢀproducts. Therefore, further prolonging reaction time made no sense on the styrene
epoxidation after 48 h. There is no doubt that the reaction time played a key role in
styrene epoxidation reaction. The results showed that the optimal reaction time was
4
5
8 h. The conversion of styrene was 72.1% and the selectivity of styrene oxide was
9.5%. The yield of styrene oxide was 42.9%. What’s more, the joint selectivity of
styrene oxide and benzaldehyde reached 93.3%.
In addition, the catalytic performance of 4Aꢀzeolite and blank control group were
investigated under the 24 h. The catalytic results of 4Aꢀzeolite, Ag/4Aꢀzeolite and
blank control were shown in Table 3. Compared with the blank, 4Aꢀzeolite slightly
improved the conversion of styrene and selectivity of styrene oxide. It was shown that
the conversion of styrene increased slightly while the selectivity of styrene oxide
increased obviously from 18.2% to 50.4% when Ag NPs were added to the 4Aꢀzeolite.
What’s more, the selectivity of benzaldehyde and other byꢀproducts decreased
obviously. The yield of styrene oxide increased from 9.7% to 27.8%. So the Ag
NPs/4Aꢀzeolite composite catalyst showed sufficient capacity on styrene epoxidation.
1
6

Page 17 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
Table 1 Epoxidation of styrene under various catalyst dosages
Entry
Catalyst
g)
Time
(h)
Conversion
(%)
Selectivity (%)
(
SO
BZ
Others
1
0.1
0.2
0.3
0.4
0.5
24
24
24
24
24
55.1
53.2
53.9
53.0
53.3
50.4
56.1
59.0
58.1
53.0
32.8
35.7
33.2
35.6
27.7
16.8
8.2
7.8
6.3
19.3
2
3
4
5
Table 2 Epoxidation of styrene under various reaction times
Entry
Catalyst
g)
Time
(h)
Conversion
(%)
Selectivity (%)
(
SO
BZ
Others
1
2
3
4
5
0.1
0.1
0.1
0.1
0.1
12
24
36
48
60
35.9
55.1
66.4
72.1
77.8
45.5
50.4
56.4
59.5
45.9
40.4
32.8
30.3
33.8
28.7
14.1
16.8
13.3
6.7
25.3
Table 3 Comparison of Ag/4A-zeolite catalyst with the 4A-zeolite and blank control for the
styrene epoxidation reaction
Selectivity (%)
Entry
Catalyst
Time
h)
Conversion
(%)
(
SO
BZ
Others
1
-
24
51.9
16.3
46.2
37.5
4
A-zeolite
(
2
3
24
24
53.1
55.1
18.2
50.4
46.4
32.8
35.4
16.8
0.1g)
Ag/4A-zeolite
0.1g)
(
1
7

RSC Advances
Page 18 of 31
View Article Online
DOI: 10.1039/C4RA14783A
4
. Conclusions
A kind of composite catalyst involving silver NPs supported on a 4Aꢀzeolite was
prepared. The catalyst was characterized by SEM, XRD, UV, TEM and XPS. After the
analysis of all the characterization, the results showed that the 4Aꢀzeolite morphology
and crystallinity was better, and the silver NPs was proved to load onto the 4Aꢀzeolite
and evenly distributed. It was shown that the diameter of silver NPs was from 5 to 15
nm according to the figure of particle size distribution. Then the composite catalyst
was used to the epoxidation of styrene with TBHP as oxidant. The different
parameters such as catalyst amount and reaction time were investigated. The optimal
catalyst amount was 0.1 g and the optimal reaction time was 48 h. The Ag
NPs/4Aꢀzeolite composite catalyst showed good catalytic activity for the epoxidation
of styrene. The conversion of styrene was 72.1% and the selectivity of SO was 59.5%.
In addition, the joint selectivity of SO and BZ was 93.3%. We could conclude that the
0
Ag which was added to the 4Aꢀzeolite promoted the epoxidation of styrene. It would
improve the specific surface area of nanoparticles and increase the contact area
between Ag NPs and reactant that Ag NPs were added to 4Aꢀzeolite support. What’s
more, the catalytic performance would be improved when Ag NPs were distributed
very uniformly on the surface of 4Aꢀzeolite. The highly dispersive Ag NPs
significantly improve the yield of styrene oxide.
1
8

Page 19 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
REFERENCES
[
1] A. Mayoral, T. Carey, P. A. Anderson, Microporous and Mesoporous Materials,
012, 166, 117ꢀ122.
2
[
[
[
[
[
2] D. H. Kim, J. Kim, Journal of Phsics and Chemistry of Solids, 2007, 68, 734.
3] C. W. Kim, J. S. Park, K. S. Lee, Power Sources, 2006, 163, 144.
4] Bibby, M. P. Dale, Nature, 1985 (317), 157ꢀ158.
5] G. G. Lenzi, C. V. B. Favero, Desalination, 2011, 270 (1ꢀ3), 241ꢀ247.
6] H. Shiomi, H. Furukawa, Journal of Materials Science-Materials in Electronics,
2
000, 11 (1), 7ꢀ31.
7] M. D. Morris, Spie-int Soc Optical Engineering, 1999, 224ꢀ229.
8] S. Yang, W. Cai, G. Liu, Journal of Physical Chemistry C, 2009, 113 (16),
480ꢀ6484.
9] H. Muto, K. Yamada, K. Miyajima and F. Mafune, Journal of Physical Chemistry
C, 2007, 111 (46), 17221ꢀ17226.
10] P. Liu, W. Cai and H. Zeng, Journal of Physical Chemistry C, 2008, 112 (9),
261ꢀ3266.
11] S. Hashimoto, T. Uwada, H. Masuhara and T. Asahi, Journal of Physical
Chemistry C, 2008, 112 (39), 15089ꢀ15093.
[
[
6
[
[
3
[
[
12] K. Wegner, B. Walker, S. Tsantilis and S. E. Pratsinis, Chemical Engineering
Science, 2002, 57 (10), 1753ꢀ1762.
[
13] C. C. Chen, C. C. Yeh, Advanced Materials, 2000, 12 (10), 738ꢀ741.
1
9

RSC Advances
Page 20 of 31
View Article Online
DOI: 10.1039/C4RA14783A
[
14] Z. S. Pillai, P. V. Kamat, Journal of Physical Chemistry B, 2004, 108 (3),
45ꢀ951.
9
[
[
(
[
15] Y. Sun, B. Mayers, T. Herricks, Nano Letters, 2003, 3 (7), 955ꢀ960.
16] D. H. Chen, Y. W. Huang, Journal of colloid and interface science, 2002, 255
2), 299ꢀ302.
17] H. J. Jiang, K. S. Moon1, Z. Q. Zhang, Journal of Nanoparticle Research, 2006,
8
, 117ꢀ124.
[
[
[
18] C. Zakri, P. Poulin, Nano Letters, 2005, 5 (11), 2212ꢀ2215.
19] K. A. Bethke, H. H. Kung, Journal of Catalysis, 1997, 172 (1), 93ꢀ102.
20] Li. Z, Flytzani. S. M, Journal of Catalysis, 1999, 182 (2), 313ꢀ327.
[
21] H. Nakajima, S. Takase, H. Terano and H. Tanaka, Journal of Antibiotics, 1997,
0, 96ꢀ99.
22] H. Liu, J. Bai, C. P. Li, W. Xu, W. Y. Sun, T. Xu, Y. R. Huang and H. Q. Li,
RSC Advances, 2014, 4, 3195ꢀ3200.
5
[
[
[
23] B. Singh, A. K. Sinha, Journal of Materials Chemistry A, 2014, 2, 1930ꢀ1939.
24] Z. Q. Shi, L. X. Jiao, J. Sun, Z. B. Chen, Y. Z. Chen, X. H. Zhu, J. H. Zhou, X. C.
Zhou, X. Z. Li and R. Li, RSC Advances, 2014, 4, 47ꢀ53.
25] H. Liu, J. Bai, S. Wang, C. P. Li, L. P. Guo, H. O. Liang, T. Xu, W. Y. Sun and
H. Q. Li, Colloids and Surfaces A, 2014, 448, 154ꢀ159.
[
[
[
26] H. Lin, Y. Liu and Z. L. Wu, Chemical Communications, 2011, 47, 2610ꢀ2612.
27] L. Zhou, C. F. Gorin and R. J. Madix, Journal of the American Chemical Society,
2
010, 132, 434ꢀ435.
2
0

Page 21 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
[
28] M. Silva, C. Freire, B. De Castro, J. L. Figueiredo, Journal of Molecular
Catalysis A, 2006, 258, 327ꢀ333.
[
29] X. T. Wang, Z. Q. Liang, F. Z. Zhang, L. Yang and S. L. Xu, Journal of
Materials Science, 2013, 48, 5899ꢀ5903.
[
30] J. Sun, Q. B. Kan, Z. F. Li, G. L. Yu, H. Liu, X. Y. Yang, Q. S. Huo and J. Q.
Guan, RSC Advances, 2013, 4, 2310ꢀ2317.
31] M. M. Hussain and P. J. Walsh, Accounts of Chemical Research, 2008, 41,
83–893.
32] D. S. Pinnaduwage, L. Zhou, W. W. Gao and C. M. Friend, Journal of the
American Chemical Society, 2007, 129, 1872–1873.
33] J. H. Liu, F. Wang, S. S. Qi, Z. G. Gu and G. D. Wu, New Journal of Chemistry,
013, 37, 769–774.
[
8
[
[
2
2
1

RSC Advances
Page 22 of 31
View Article Online
DOI: 10.1039/C4RA14783A
Figure Captions:
Fig. 1 Scheme of preparing the Ag NPs/4Aꢀzeolite composite catalyst and chemical
equation of styrene epoxidation.
Fig. 2 SEM images of the 4Aꢀzeolite (A) and Ag NPs/4Aꢀzeolite composite catalyst
(B); EDS spectra of Ag NPs/4Aꢀzeolite composite catalyst (C).
Fig. 3 XRD patterns of the 4Aꢀzeolite (A); Ag NPs/4Aꢀzeolite composite catalyst (B).
Fig. 4 SolidꢀUV spectra pattern of the Ag NPs/4Aꢀzeolite composite catalyst (A) and
liquidꢀUV spectra pattern of the filtrate (B).
Fig. 5 TEM images of Ag NPs/4Aꢀzeolite composite catalyst (A and B) and HRTEM
image of Ag NPs/4Aꢀzeolite composite catalyst (C).
Fig. 6 XPS pattern of the Ag NPs/4Aꢀzeolite composite catalyst.
Table 1 Epoxidation of styrene under various catalyst dosages.
Table 2 Epoxidation of styrene under various reaction times.
Table 3 Comparison of Ag/4Aꢀzeolite catalyst with the 4Aꢀzeolite and blank control for the
styrene epoxidation reaction
.
2
2

Page 23 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
Fig. 1
2
3

RSC Advances
Page 24 of 31
View Article Online
DOI: 10.1039/C4RA14783A
C
Fig. 2
2
4

Page 25 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
B
A
44.3
38.1
64.5
10
20
30
40
50
60
70
80
2-Theta(degree)
Fig. 3
2
5

RSC Advances
Page 26 of 31
View Article Online
DOI: 10.1039/C4RA14783A
383nm
A
B
413nm
300
400
500
600
Wavelength(nm)
Fig. 4
2
6

Page 27 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
A
B
2
7

RSC Advances
Page 28 of 31
View Article Online
DOI: 10.1039/C4RA14783A
C
D
Fig. 5
2
8

Page 29 of 31
RSC Advances
View Article Online
DOI: 10.1039/C4RA14783A
500000
400000
300000
200000
100000
0
A
Ag(3d)
Na(1s)
Al(2p)
O(1s)
C(1s)
Si(2p)
1200
1000
800
600
400
200
0
Binding Energy (eV)
100000
3
68.5
B
80000
60000
40000
20000
0
3
74.5
390
385
380
375
370
365
Binding Energy (eV)
Fig. 6
2
9