Aluminium-rich Beta zeolite-supported platinum nanoparticles for the low-temperature catalytic removal of toluene

Article abstract of DOI:10.1039/c4ta06407k

The removal of volatile organic compounds is an important aspect of sustainability and environmental protection. Catalytic oxidation is one of the most efficient routes to achieve this. The K⁺ form of an aluminium-rich Beta zeolite-supported Pt nanoparticle (2.2 nm) [Pt/KBeta-seed-directed synthesis (SDS)] catalyst is very active for the low-temperature catalytic removal of toluene and results in full conversion at a much lower temperature than a conventional KBeta-supported Pt nanoparticle (Pt/KBeta-TEA) catalyst. The higher activity of the Pt/KBeta-SDS catalyst compared with the Pt/KBeta-TEA catalyst is related to the advantages of the higher K⁺ content and fewer terminal silanol defects in the KBeta-SDS catalyst than in the KBeta-TEA catalyst. The higher K⁺ content is helpful for the formation of more Pt⁰ species, and both the higher K⁺ content and the lower number of terminal silanol defects are favourable for the adsorption of toluene, as evidenced by XPS and the toluene-TPD profiles. More importantly, the Pt/KBeta-SDS catalyst shows very stable activities in the presence of H₂O and CO₂ in the feed gases. The combination of this extraordinary activity and excellent stability in the catalytic removal of toluene over the Pt/KBeta-SDS catalyst are important for future environment protection.

Full text of DOI:10.1039/c4ta06407k

Journal of
Materials Chemistry A
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PAPER
Aluminium-rich Beta zeolite-supported platinum
nanoparticles for the low-temperature catalytic
removal of toluene†
Cite this: J. Mater. Chem. A, 2015, 3,
556
5
Chunyu Chen, Qinming Wu, Fang Chen, Ling Zhang, Shuxiang Pan, Chaoqun Bian,
Xiaoming Zheng, Xiangju Meng* and Feng-Shou Xiao
The removal of volatile organic compounds is an important aspect of sustainability and environmental
+
protection. Catalytic oxidation is one of the most efficient routes to achieve this. The K form of an
aluminium-rich Beta zeolite-supported Pt nanoparticle (2.2 nm) [Pt/KBeta-seed-directed synthesis (SDS)]
catalyst is very active for the low-temperature catalytic removal of toluene and results in full conversion
at a much lower temperature than a conventional KBeta-supported Pt nanoparticle (Pt/KBeta-TEA)
catalyst. The higher activity of the Pt/KBeta-SDS catalyst compared with the Pt/KBeta-TEA catalyst is
+
related to the advantages of the higher K content and fewer terminal silanol defects in the KBeta-SDS
+
0
catalyst than in the KBeta-TEA catalyst. The higher K content is helpful for the formation of more Pt
+
species, and both the higher K content and the lower number of terminal silanol defects are favourable
Received 24th November 2014
Accepted 15th January 2015
for the adsorption of toluene, as evidenced by XPS and the toluene-TPD profiles. More importantly, the
2 2
Pt/KBeta-SDS catalyst shows very stable activities in the presence of H O and CO in the feed gases. The
DOI: 10.1039/c4ta06407k
combination of this extraordinary activity and excellent stability in the catalytic removal of toluene over
the Pt/KBeta-SDS catalyst are important for future environment protection.
www.rsc.org/MaterialsA
mesoporous ZrO2 impregnated with 0.5% Pd have been
compared as catalysts for the total oxidation of toluene; the
1
. Introduction
Volatile organic compounds (VOCs), which are emitted from combination of Pd/FAU zeolite had a higher activity than Pd
motor vehicles and industrial processes as well as from indoor loaded onto conventional ZrO and macro-mesoporous
Other workers have found that Pt/HFAU and Pt/HBEA
formaldehyde and halogenated hydrocarbons are precursors of exhibited very good activities in the catalytic oxidation of o-
2
21–23
2
compounds, are major air pollutants. VOCs such as toluene, ZrO .
2
4–28
ozone and photochemical smog, which are harmful to human xylene, methyl-isobutyl-ketone and dichloromethane.
In
1–4
health. The complete removal of VOCs has received much addition, we found that ZSM-5-supported Pt catalysts had a
attention and catalytic oxidation has been identied as one of superior performance in the catalytic removal of toluene. In
+
the most effective and economically feasible routes for VOCs particular, it was shown that K -exchanged ZSM-5 exhibited a
+
+
abatement without the creation of further toxic by-products, better performance than the H and Na forms of zeolites and
+
especially for low concentrations of VOCs at low that the K content in ZSM-5 was positively correlated with the
5
–18
31
temperatures.
catalytic activity in the removal of VOCs.
+
Zeolite-supported noble metal nanoparticles have been
In general, the K content of zeolites is dependent on the ion-
proved to be superior catalysts for the removal of VOCs as a exchange capacity, which is associated with the Al species in the
result of a combination of the advantages of the zeolites (large zeolite framework. For conventional Beta zeolite (Beta-TEA)
surface area, high adsorption capacity, acid–base properties synthesized in the presence of tetraethylammonium cations
+
and high stability) and the noble metals (high activity and (TEA ), the Si : Al ratios are usually >12. However, the template-
19–32
19,20
stability).
For example, Becker and Forster
studied the free and seed-directed synthesis (SDS) of Beta zeolite (Beta-SDS)
oxidative decomposition of benzene and its methyl derivatives shows that the Si : Al ratios in this zeolite may be as low as 4,
over NaY, CuY, PdHY and PdY zeolites; PdY was the most active which signicantly increases the Al species in the Beta frame+-
catalyst. The FAU zeolite, ZrO2 and hierarchical macro- work. This feature is favourable for the introduction of more K
3
3–36
into the Beta zeolite.
Beta-SDS has fewer terminal silanol
which is favourable for the adsorp-
33,36
defects than Beta-TEA,
Key Lab of Applied Chemistry of Zhejiang Province and Department of Chemistry,
Zhejiang University, Hangzhou 310007, China. E-mail: mengxj@zju.edu.cn
tion of the hydrophobic molecules of VOCs.
We report here the successful synthesis of an aluminium-
†
Electronic supplementary information (ESI) available: Supplementary tables
+
rich Beta zeolite with a relatively high K content and few
and gures. See DOI: 10.1039/c4ta06407k
5556 | J. Mater. Chem. A, 2015, 3, 5556–5562
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terminal silanol defects (KBeta-SDS) compared with conven- HCl (pH 3–4), collected by centrifugation and dispersed in
39
tional Beta zeolite. The KBeta-SDS-supported Pt nanoparticles ethanol containing 40 mg PVP.
Pt/KBeta-SDS) exhibited extraordinary catalytic activity. The Pt/ KBeta zeolite-supported Pt nanoparticle catalysts were
KBeta-SDS also showed excellent catalytic stability, even in the prepared by loading Pt nanoparticles onto the KBeta zeolites. In
(
presence of H
2
O and CO
2
in the feed gases.
a typical run, a measured amount of KBeta was added into 50
mL of ethanol containing an appropriate amount of Pt nano-
particles, followed by stirring at room temperature for 12 h. The
solid product was nally obtained by ltration or centrifuga-
2. Experimental
ꢀ
tion, washed with ethanol, dried at 80 C in air for 12 h, calcined
2.1 Materials
ꢀ
ꢀ
at 350 C in air for 12 h and reduced at 300 C in an H ow for
2
2
NaAlO
2
, NaOH, HCl, ethanol and toluene were purchased from
39
h. In this work, KBeta-SDS- and KBeta-TEA-supported
Sinopharm Chemical Reagent. Fumed silica (SiO2) was
Pt nanoparticle catalysts are denoted as Pt/KBeta-SDS and
Pt/KBeta-TEA; these samples without reduction are denoted as
purchased from Shenyang Chemical Co. Beta seeds (Si : Al ¼
12.50) were purchased from Nankai University Catalyst Co.
Pt/KBeta-SDS-unreduced
respectively.
and
Pt/KBeta-TEA-unreduced,
Tetraethylammonium hydroxide solution (2.0 M in H
supplied by BASF. H PtCl $6H O, ethylene glycol and KCl were
purchased from Aladdin. Polyvinylpyrrolidone (PVP, M
9 000) was purchased from Sigma-Aldrich. All these chemicals
2
O) was
2
6
2
w
¼
2.3 Characterization
2
X-ray diffraction (XRD) patterns were obtained using a RIGAKU
Ultimate IV diffractometer with Cu Ka radiation. Nitrogen
sorption isotherms at ꢁ196 ꢀC were measured using Micro-
meritics ASAP 2020M and Finetec Finesorb-3020 systems. The
surface area was calculated by using the Brunauer–Emmett–
Teller (BET) method. The elemental composition of the zeolites
and the Pt content in the catalysts were determined by induc-
tively coupled plasma atomic emission spectrometry (ICP-AES)
using a Perkin-Elmer plasma 8000 optical emission spectrom-
eter. The X-ray photoelectron spectra (XPS) of the catalysts were
recorded using a Thermo ESCALAB 250 instrument with Al Ka
X-ray radiation for the X-ray source. The binding energies were
calibrated against the C1s (285.0 eV) and Al2p (73.9 eV) peaks.
Temperature-programmed desorptions of toluene (toluene-
TPD) were performed on a Finetec Finesorb-3010 instrument
equipped with a thermal conductivity detector. In a typical run,
were of analytical-reagent grade and were used without further
purication.
2.2 Preparation
The template-free and SDS of Beta zeolite (Beta-SDS) was carried
34
out in the presence of calcined Beta zeolite seeds. In a typical
run, 0.32 g of NaAlO and 0.56 g of NaOH were dissolved in 6.8
mL of H O, followed by the addition of 2.0 g of fumed silica.
2
2
Aer stirring for 12 h, 0.1 g of Beta zeolite seeds was introduced
into the gel and stirred for 10 min. The resultant gel was
ꢀ
transferred into an autoclave to crystallize at 120 C for 90 h.
The solid product was ltered, washed with water and dried at
ꢀ
8
0 C in air for 12 h. For comparison, conventional Beta zeolite
+
(
Beta-TEA) was synthesized in the presence of TEA . In a typical
run, 0.15 g of NaAlO and 0.08 g of NaOH were dissolved in 6.3
mL of H O, followed by the addition of 9.7 mL of tetraethy-
2
1
0 mg of sample were pre-treated in a pure He ow (15 mL
2
ꢁ
1
ꢀ
ꢀ
min ) at 200 C for 0.5 h and then cooled down to 50 C prior to
lammonium hydroxide solution. Aer stirring for 10 min, 2.4 g
of fumed silica were introduced into the gel and the mixture was
stirred for 12 h. The resultant gel was transferred into an
the adsorption of toluene for 2 h. Aer saturation with toluene,
ꢁ
1
the sample was ushed with pure He (15 mL min ) for 2 h at
ꢀ
5
0 C. The desorption proles of toluene-TPD were recorded
ꢀ
autoclave to crystallize at 140 C for 96 h. The solid product was
ꢀ
ꢁ1
online at a heating rate of 10 C min . Scanning electron
microscopy (SEM) images were recorded on a Hitachi SU 1510
apparatus. Transmission electron microscopy (TEM) and elec-
tron diffraction (ED) experiments were performed at 100 kV on a
Hitachi HT-7700 electron microscope. High-resolution TEM
ꢀ
centrifuged, washed with water, dried at 80 C in air for 12 h and
ꢀ
calcined at 550 C for 5 h to remove the organic template. The
+
K -exchanges of the Beta zeolite were performed with 1 M KCl
solution. In a typical run, 1.0 g of Beta zeolite was added into 50
mL of KCl solution, followed by stirring at room temperature for
(HRTEM) images were obtained at 200 kV on a JEOL 2100F
3
h. The solid product was ltered or centrifuged, washed with
electron microscope.
ꢀ
+
water and dried at 80 C in air for 12 h. To decrease the Na
concentration in the samples, the ion-exchange procedures
were repeated once more.
2.4 Catalytic evaluation
Pt nanoparticles were synthesized by a previously reported Experiments for the catalytic removal of 1000 ppm toluene were
3
7,38
polyol reduction method.
NaOH (0.22 g, 20 mL) was added into an ethylene glycol solution bed microreactor consisting of a quartz tube (6 mm i.d.) lled
of H PtCl $6H O (20 mL) and stirred at room temperature for 1 with the catalyst. A typical experiment was performed using a
h; a transparent yellow suspension was obtained. Aer heating catalytic bed of 100 mg catalyst (0.45–0.90 mm size) with a total
In a typical run, a solution of performed at atmospheric pressure in a continuous-ow xed-
2
6
2
ꢀ
ꢁ1
at 90 C for 2 h with an N ow passing through the reaction ow-rate of feed gases (79% N + 21% O ) of 100 mL min
,
2
2
2
ꢁ1
ꢁ1
system, a transparent dark brown homogeneous colloidal giving a space velocity (SV) of 60 000 mL g
solution of Pt nanoparticles was obtained without any precipi- humidity (RH) of the feed gases was determined by a high-
tate. The Pt nanoparticles were precipitated by adding 0.3 M accuracy thermo-hygrometer with probe (WSB-2-H2,
h . The relative
a
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Zhengzhou Boyang). The concentration of toluene in the tail Fig. S2A† shows the XRD patterns of the various KBeta-based
gases was analysed using a gas chromatograph (Kexiao, samples, which exhibit well-resolved characteristic peaks asso-
GC1690) equipped with a ame ionization detector and a ciated with the BEA zeolite structure. Fig. S2B† shows the N2
1
9091N-113 INNOWAX capillary column (Agilent, 30 m ꢂ 0.32 sorption isotherms of these samples and their textural param-
mm ꢂ 0.25 mm i.d.). The concentration of the oxidative prod- eters are summarized in Table S2.† These results indicate that
ucts (CO and CO) in the tail gases was analysed with a gas both KBeta-SDS and KBeta-TEA retain their textures aer
chromatograph (Kexiao, GC1690) equipped with a thermal loading with Pt nanoparticles.
conductivity detector using a Carboxen packed column (JieDao, Fig. 2 shows TEM images and the Pt nanoparticle size
2
2
m ꢂ 2 mm). The conversion of toluene was calculated from distributions of Pt/KBeta-SDS and Pt/KBeta-TEA, indicating that
the difference in the inlet and outlet concentrations of toluene. both catalysts have a similar Pt particle size, with a distribution
The selectivity to CO was calculated from the consumption of of 2.2 ꢃ 0.4 nm. These results suggest that the Pt nanoparticle
2
toluene and the outlet concentration of CO . The carbon size distribution is unchanged aer the loading process. The
2
balance reached 100 ꢃ 5% in this work. The catalytic activities HRTEM images of these catalysts (insets, Fig. 2A) also show a Pt
42
5
were determined by the values of T , T50 and T98, which were lattice with a Pt(111) interlayer spacing of 0.23 nm.
dened as the temperatures at 5%, 50% and 98% of toluene
conversion, respectively.
Table 1 gives the elemental composition of Pt/KBeta-SDS and
Pt/KBeta-TEA, indicating that both samples have a similar Pt
+
+
loading (about 1.1%), but different K contents. The K content
of Pt/KBeta-SDS is almost three times that of Pt/KBeta-TEA.
Fig. S3† shows the Pt4f XPS spectra of various KBeta-based
3. Results and discussion
0
2+
samples. Aer deconvolution, the ratios of Pt /Pt in the
3
.1 Sample preparation and characterization
.1.1 As-synthesized Beta-SDS and Beta-TEA zeolites.
Fig. S1† shows the XRD patterns, N sorption isotherms and
0
2+
various samples could be estimated (Table 2). The Pt /Pt ratios
of the Pt/KBeta-SDS samples were higher than those of the Pt/
3
2
+
KBeta-TEA samples, conrming that a higher K content is
SEM images of the as-synthesized Beta-SDS and Beta-TEA
samples. The XRD patterns show that both samples had well-
resolved characteristic peaks associated with the BEA structure.
0
favourable for the formation of more Pt species, which are
regarded as catalytically active centres for the conversion of
24,30,31
+
toluene into CO and H O.
The effect of the K ions on the
2
0
2
The N sorption isotherms show that the as-synthesized Beta-
2
formation of Pt species is suggested by the interaction between
the framework oxygen with the Pt nanoparticles (Pt–zeolite
interaction), where the framework oxygen in the zeolite is
SDS already had open micropores, whereas the as-synthesized
Beta-TEA had no open micropores. The SEM images show that
both samples had a similar morphology, with almost uniform
crystals of about 100–160 nm.
+
strongly inuenced by the presence of K ions. This Pt–zeolite
43–47
interaction has been reported previously.
For example,
3.1.2 Pt nanoparticles. The Pt nanoparticles in this
Treesukol et al. reported that an interaction took place by
electron transfer from the framework oxygen to the Pt atom in
research were synthesized by a polyol reduction method. Fig. 1
shows the TEM images and size distribution of the Pt nano-
particles; the Pt nanoparticles were 2.2 ꢃ 0.4 nm in size. The ED
pattern of the Pt nanoparticles corresponded to the (111), (200),
40
(220), (311) and (222) planes of the face-centred cubic lattice.
The HRTEM image of the Pt nanoparticles in the samples
clearly showed the lattice fringes with interplanar distances of
41
0.23 nm, corresponding to Pt(111) planes.
3.1.3 KBeta zeolite-supported Pt nanoparticle catalysts.
The KBeta zeolite-supported Pt nanoparticle catalysts were
prepared by loading Pt nanoparticles onto the KBeta zeolites.
Fig. 1 (a) TEM image, (b) ED pattern, (c) HRTEM image and (d) size Fig. 2 (A) TEM images (inset, HRTEM images) and (B) Pt nanoparticle
distribution of Pt nanoparticles.
size distributions of (a) Pt/KBeta-SDS and (b) Pt/KBeta-TEA.
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Table 1 Elemental composition of Pt/KBeta-SDS and Pt/KBeta-TEA
3.2 Catalytic performance
a
ꢁ1
3.2.1 Comparison of Pt/KBeta-SDS with Pt/KBeta-TEA.
Sample
Si : Al ratio
K (mg g
)
Pt content (%)
Fig. 4 shows the dependence of the catalytic activities on the
reaction temperature in the catalytic oxidation of toluene
over the Pt/KBeta-SDS, Pt/KBeta-TEA, Pt/KBeta-SDS-unre-
duced and Pt/KBeta-TEA-unreduced catalysts. The conver-
sion of toluene increases rapidly at a certain temperature. It
is possible that the actual temperature of the catalytic site is
higher than the recorded value as a result of an exothermic
reaction. However, it is believed that the temperature at
which the conversion is rapidly increased, the ignition
temperature, or the temperature at which there is almost full
conversion, may be a measure of the catalytic activity.
Pt/KBeta-SDS
Pt/KBeta-TEA
3.90
10.66
9.72
3.30
1.15
1.07
a
Determined from ICP-AES measurements.
Table 2 XPS results for the various samples
Peak area
Pt4f7/2
0
2+a
Sample
Pt species
Pt4f5/2
Pt /Pt
5
Therefore T , T50 and T98 are used to compare the activities of
0
Pt/KBeta-SDS
Pt
781
202
477
198
410
164
385
209
588
152
359
149
308
124
289
157
3.9
2.4
2.5
1.8
2+
0
2+
0
2+
0
2+
the catalysts (Table 3). The activities of the reduced catalysts
are higher than those of the unreduced catalysts and are
Pt
Pt
Pt
Pt
Pt
Pt
Pt
Pt/KBeta-SDS-unreduced
Pt/KBeta-TEA
0
positively related to the proportion of Pt species in the
catalysts, as observed from the XPS results (Table 2). These
0
results suggest that the Pt species may be the active centres
Pt/KBeta-TEA-unreduced
2
4,30,31
2 2
for the conversion of toluene into CO and H O.
It was also found that Pt/KBeta-SDS was more active than
a
Peak area ratio.
Pt/KBeta-TEA. For example, Pt/KBeta-SDS gives a T98 for
ꢀ
toluene as low as 150 C, which is lower than that of Pt/KBeta-
ꢀ
TEA (160 C; Table 3). This may be interpreted as a result of
+
the difference in the content of K and terminal silanol
43
the Pt/ZSM-5 sample; Koningsberger and coworkers showed
that the metals at the interface may be sufficiently polarized to
bond with the oxygen of supports such as zeolites.
+
3
3–36
defects.
A higher K content should result in both the
0
formation of more Pt species and a stronger adsorption of
toluene in the catalysts (Table 2, Fig. 3); fewer terminal sila-
nol defects favour the stronger adsorption of toluene
Fig. 3), which is helpful for the activation of toluene for
conversion to CO and H O.
.2.2 Activities of Pt/KBeta-SDS under various conditions.
44–46
Fig. 3 shows the toluene-TPD proles of Pt/KBeta-SDS and Pt/
KBeta-TEA. Both samples gave three peaks, but Pt/KBeta-SDS
showed much higher desorption temperatures (75, 160 and
3
3,36
(
2
2
ꢀ
ꢀ
3
45 C) than Pt/KBeta-TEA (75, 148 and 275 C), suggesting that
3
Pt/KBeta-SDS adsorbs toluene more strongly than Pt/KBeta-TEA.
This phenomenon could be reasonably assigned to the higher
K content and fewer terminal silanol defects in KBeta-SDS than
Fig. 5 shows the activities of Pt/KBeta-SDS in the catalytic
oxidation of toluene under feed gases with various RH and CO2
+
concentrations; the T
. The activity of the Pt/KBeta-SDS catalyst reduces slightly when
the RH of the feed gases is 50%, indicating that there is an
inhibition effect of H O as a result of the competitive adsorption
of H O in the oxidation reaction.
5
, T50 and T98 values are presented in Table
33–36,48,49
48
in KBeta-TEA.
Yoshimoto et al. comprehensively and
4
quantitatively analysed the adsorption behaviour of toluene on
alkaline-containing zeolites using a TPD method and reported
that approximately one toluene molecule was adsorbed on one
alkali cation in BEA and MFI zeolites at high temperatures.
2
31,50
2
However, the presence of
Fig. 4 Catalytic oxidation of toluene over the Pt/KBeta-SDS, Pt/
KBeta-TEA, Pt/KBeta-SDS-unreduced and Pt/KBeta-TEA-unreduced
catalysts.
Fig. 3 Toluene-TPD profiles of Pt/KBeta-SDS and Pt/KBeta-TEA.
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Table 3 Catalytic data for toluene oxidation over the Pt/KBeta-SDS
and Pt/KBeta-TEA catalysts
ꢀ
Activity ( C)
Catalyst
T
5
T
50
T
98
Pt/KBeta-SDS
Pt/KBeta-TEA
Pt/KBeta-SDS-unreduced
Pt/KBeta-TEA-unreduced
101
135
132
152
142
157
152
167
150
160
159
175
Fig. 6 Dependence of activities on reaction time in the catalytic
oxidation of toluene over Pt/KBeta-SDS at temperatures of (a) 150, (b)
ꢀ
1
50 and (c) 160 C in the absence or presence of CO
2
(5%) and H
2
O
(50% RH).
inhibition effect of H O is reversible. When the reaction
2
ꢀ
temperature was increased to 160 C, there was no signicant
decrease in the conversion of toluene during 20 h tests, even in
Fig. 5 Catalytic oxidation of toluene over the Pt/KBeta-SDS catalyst
under feed gases with various RH and CO concentrations.
the presence of CO
2
and H
2
O (Fig. 6c). These results indicate
O could be completely avoided at
2
that the inhibition effect of H
2
ꢀ
160 C.
Fig. 7 shows the effect of the SV on activity in the catalytic
oxidation of toluene over Pt/KBeta-SDS; the T , T50 and T98
Table 4 Catalytic data for toluene oxidation over the Pt/KBeta-SDS
5
catalyst under feed gases with various RH and CO
2
concentrations
values are presented in Table 5. When the SV was 30 000 mL
ꢀ
ꢁ1 ꢁ1
Activity ( C)
g
h
, the T , T and T98 values of the catalyst were 86, 142
5 50
ꢀ
ꢁ1
and 148 C, respectively. When the SV reached 60 000 mL g
h
a
RH (%)
CO
2
concentration (%)
T
5
T
50
T
98
ꢁ
1
ꢀ
5
, the T , T50, and T98 values were 101, 142, and 150 C,
ꢁ1
ꢁ1
0
0
0
5
5
101
130
107
126
142
147
142
147
150 respectively. Increasing the SV to 120 000 mL g
h
5
, the T ,
ꢀ
5
0
5
0
0
160
150
160
T
50 and T98 values were 111, 143 and 155 C, respectively.
These values are much lower than those reported previ-
8,9,23,51,52
ously
(Table 5). These results show that
a
Relative humidity.
Pt/KBeta-SDS is an active catalyst for the catalytic removal of
VOCs.
5
% CO
2
in the feed gases did not inuence the catalytic activity,
. Even in
, only the inhibition effect of
indicating that there was no inhibition effect from CO
the presence of both H O and CO
2
2
2
H O was observed, indicating that there was no synergistic
2
inhibition effect of H O and CO .
2
2
Fig. 6 shows the dependence of the catalytic activities on
reaction time in the catalytic oxidation of toluene over Pt/KBeta-
ꢀ
SDS at 150 and 160 C in the absence or presence of CO
2
and
2
H O. Neither CO nor small organic molecules could be detected
in the tail gases; CO
2
and H
2
O were the only products observed.
ꢀ
When the reaction temperature was 150 C, the activity was very
stable during 20 h tests (Fig. 6a). There was no loss of activity
aer the addition of CO . However, the addition of H O leads to
2
2
an obvious reduction in the conversion of toluene (Fig. 6b). The
toluene conversion could be completely recovered by stopping
Fig. 7 Catalytic oxidation of toluene over Pt/KBeta-SDS under various
2
the addition of H O in the feed gases, indicating that the SV values.
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Table 5 Catalytic data for oxidation of toluene over various catalysts
ꢀ
Activity ( C)
a
ꢁ1 ꢁ1
b
Catalyst
SV [mL g
h
]
C
toluene (ppm)
T
5
T
50
T
98
Ref.
Pt/KBeta-SDS
30 000
1000
86
101
111
142
142
143
148
150
155
260
265
260
230
180
This work
6
1
0 000
20 000
Mn0.5Ce0.5
50 000
40 000
153 000
60 000
20 000
600
1000
225
1000
1000
51
8
52
23
9
LaMnO
% Pt/Al
Pd–Au/TiO
3
1
2
O
3
2
6
.4% Au/LaSrMnO
3
a
b
Space velocity. Concentration of toluene.
9
Y. X. Liu, H. X. Dai, J. G. Deng, X. W. Li, Y. Wang,
H. Arandiyan, S. H. Xie, H. G. Yang and G. S. Guo, J. Catal.,
2013, 305, 146.
4
. Conclusions
+
The K form of an aluminium-rich Beta-supported Pt nano-
particle catalyst (Pt/KBeta-SDS) was successfully prepared and 10 C. He, J. J. Li, P. Li, J. Cheng, Z. P. Hao and Z.-P. Xu, Appl.
tested for the catalytic removal of 1000 ppm toluene. The results
Catal., B, 2010, 96, 466.
show that the Pt/KBeta-SDS catalyst is very active, giving a T98 11 C. He, F. W. Zhang, L. Yue, X. S. Shang, J. S. Chen and
ꢀ
value as low as 150 C. The superior activity was positively
Z. P. Hao, Appl. Catal., B, 2012, 111, 46.
0
related to the Pt/KBeta-SDS with a high content of Pt species 12 Z. Z. Zhu, G. Z. Lu, Z. G. Zhang, Y. Guo, Y. L. Guo and
and strong toluene adsorption, which may be reasonably
Y. Q. Wang, ACS Catal., 2013, 3, 1154.
attributed to the abundant K species and the few terminal 13 H. Huang, Q. G. Dai and X. Y. Wang, Appl. Catal., B, 2014,
silanol defects of KBeta-SDS. More importantly, the addition of
158, 96.
CO and H
O in the feed gases does not inuence the activities 14 D. Y. C. Leung, X. L. Fu, D. Q. Ye and H. B. Huang, Kinet.
+
2
2
of the Pt/KBeta-SDS catalyst when the reaction temperature is
>
Catal., 2012, 53, 239.
ꢀ
160 C. This feature is potentially important in future practical 15 A. M. Harling, D. J. Glover, J. C. Whitehead and K. Zhang,
applications of this catalyst.
Environ. Sci. Technol., 2008, 42, 4546.
16 H. C. Genuino, S. Dharmarathna, E. C. Njagi, M. C. Mei and
S. L. Suib, J. Phys. Chem. C, 2012, 116, 12066.
Acknowledgements
17 Q. G. Huang, S. F. Zuo and R. X. Zhou, Appl. Catal., B, 2010,
5, 327.
9
This work was supported by the National Natural Science
Foundation of China (21422306, 21273197 and 21203165) and
the National High-Tech Research and Development Program of
China (2013AA065301).
18 B. de Rivas, R. Lopez-Fonseca, C. Jimenez-Gonzalez and
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