35 卷 6 期 2016. 6

结

构 化 学 （JIEGOU HUAXUE） Chinese J. Struct. Chem.

Vol. 35, No. 6 889─902

Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene① YU Hana② CAO Zhou-Minga WEI Xiao-Fengb YU Yana② a

(Key Laboratory of Eco-materials Advanced Technology (Fuzhou University), Fujian Province University, College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China)

b

(College of Chemical Engineering, Fuzhou University, Fuzhou 350108, China)

ABSTRACT Pt/FeSnO(OH)5 was synthesized as a novel catalyst for VOCs oxidation. Compared with Pt/γ-Al2O3 during catalytic oxidation of benzene, Pt/FeSnO(OH)5 showed better catalytic activity. After characterization of the catalysts by XRD, SEM, TEM, EDS, XPS, BET, TGA and DTA, we found most Pt could be reduced to metallic state when the hydroxyl catalyst was used as supporter, and the metallic Pt in Pt/FeSnO(OH)5 was more active than the oxidized Pt in Pt/γ-Al2O3 in catalytic oxidation of VOCs. Pt/FeSnO(OH)5 shows both good catalytic activity and high stability, which may be a promising catalyst. This study may also be helpful for the design and fabrication of new catalysts. Keywords: FeSnO(OH)5, supported Pt catalyst, catalytic oxidation of benzene; DOI: 10.14102/j.cnki.0254-5861.2011-1052 the most popular effective technologies because of

1 INTRODUCTION

its advantages such as low energy consumption, high At present, a growing number of researchers pay a close attention to the topic of removing the volatile

catalytic efficiency, relatively high flexibility and economical efficiency[2].

organic compounds (VOCs) because their extensive

Currently, supported noble metal catalysts, espe-

uses lead to water and air pollution. Among VOCs,

cially platinum (Pt) and palladium (Pd), despite their

benzene is a typical representative recognized as a

high costs, are often used in deep catalytic oxidation

[1]

major contributor to air pollution . Human and

of benzene because noble metal (Pt or Pd) can

animal are susceptible to benzene intoxication via

greatly improve the performance of catalysts for the

direct or indirect contact and will greatly increase

catalytic oxidation of benzene[1,

the risk of cancer if they live or stay in the benzene

doubt that a stable support can improve the per-

environment for a long period. Therefore, it is

formance of Pt-based catalysts[7-9]. And most of the

important to find an efficient method to get rid of

supported Pt catalysts are metal oxides, compounds

benzene. The catalytic oxidation of VOCs is one of

or nitrides as supports such as Al2O3[5, 10, 11], TiO2[1, 12, 13],

3-6]

. There is no

Received 16 November 2015; accepted 13 April 2016 ① This project was supported by the National Natural Science Foundation of China (No. 51102047, 51472050), the Natural Science Foundation of Fujian Province (No. 2013J05027) and the Fujian Province Education-science Project for Middle-aged and Young Teachers (No. JA13050) ② Corresponding author. Yu Han, Ph. D, Tel.: +86 591 22825732, Fax: +86 591 22866537. E-mails: [email protected] and [email protected]

892

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene [14]

zeolites

[3, 15]

and BN

No. 6

. These supports showed high

performances. On the basis of the characterizations,

thermal conductivity, temperature stability and

we have studied the oxidation states of Pt and the

[6, 7, 14]

oxidation resistance

. Moreover, the previous

relationship between the new support and the

researches have shown that metallic Pt nanoparticles

supported Pt for catalytic oxidation of benzene. This

have strong capacity for oxygen activation, and rich

study would be useful for the broadening of catalyst

chemisorbed oxygen on the surfaces of Pt nanopa-

supports and fabrication of efficient catalysts.

ticles is responsible for high catalytic activities for deep oxidation of benzene[1]. And a series of [3, 13]

lytic activities were observed in oxidized Pt catalysts and reduced Pt catalysts, of which the metallic species

EXPERIMENTAL

have demonstrated that different cata-

studies

[1, 2]

2

0

(Pt ) were more active than their oxidi2+

2. 1

Preparation of FeSnO(OH)5 nanocrystals

All of the chemical reagents were analytical grade from Sinopharm Chemical Reagent Co., Ltd. and

zed forms (PtO/ Pt ) for catalytic oxidation. In

used as received without further purification. The

addition, the dispersion of Pt on the supports’ sur-

solid FeSnO(OH)5 nanocrystals were prepared by an

face, the specific surface area of supports and the

ion-exchange method[20]. In a typical synthesis, 10

structure of the catalyst were also important factors

mmol of FeSO4·7H2O was added into 100 mL deio-

[1, 6, 16]

to affect the catalytic activity

.

nized water, and the solution was stirred at room

The surfaces of hydroxyl compounds possess

temperature until FeSO4·7H2O was dissolved com-

many hydroxyl (·OH) species and chemisorbed

pletely. Then, 20 mL of the solution containing 10

[17-19]

, and the rich hydroxyl species can make

mmol Na2SnO3·4H2O was poured into the FeSO4

the Pt nanoparticles strongly and balancedly loaded

solution. The mixed solution was cooled to 0 ℃

on the support surfaces, leading to better catalytic

and stirred for 6 h. After the reaction, the precipitates

activities. However, there is no report on using the

were collected by centrifugation and washed with

hydroxyl compounds as the carrier of catalysts as we

deionized water and ethanol for three times, res-

have known, because the poor thermal stability of

pectively. The final products were then dried in

most hydroxyl compounds prevents their applica-

vacuum at 70℃ for 12 h before use.

tions in catalysis. Therefore, if we can prepare a new

2. 2

oxygen

hydroxyl compound with better thermal stability

Preparation of the Pt/FeSnO(OH)5 composite catalysts

than the popular hydroxyl compounds, a new kind of

FeSnO(OH)5 loaded with 0.5 wt% Pt was fabri-

highly active supported Pt catalyst may be prepared.

cated via a simultaneous reduction-etching route[21].

However, how to achieve this target is a great

We used the L-ascorbic acid as reductant to reduce

challenge.

the H2PtCl6·6H2O in the water environment. 0.665

In this work, a new hydroxystannate compound

mL H2PtCl6·6H2O (0.019 M) was quickly added to a

(iron hydroxystannate, FeSnO(OH)5) has been

beaker of 10 mL ice water under strong stirring.

[20]

prepared via an ion exchange method

and loaded [21]

Then, 10 mL L-ascorbic acid ice-water solution (0.1

.

M) was slowly added into the solution. Next, 0.5 g

The catalyst (Pt/FeSnO(OH)5) was characterized in

as-synthesized FeSnO(OH)5 powder was dropped

detail by X-ray diffraction (XRD), infrared spec-

into the above mixed solution and stirred for 10

troscopy (FTIR), TG-DTA, field emission scanning

minutes. Subsequently, the beaker of mixture was

electron microscopy (FESEM), field emission trans-

placed in an ultrasonic cleaning instrument and

mission electron microscopy (FETEM), Brunauer-

treated for 1 h. Then the mixture was impregnated

Emmett-Teller (BET) and X-ray photoelectron spec-

and deposited for 24 h. The obtained products were

troscopy (XPS) for interpretation of its catalytic

collected by centrifugation and washed with deioni-

with Pt by simultaneous reduction-etching route

2016

Vol. 35

结

构

化

学（JIEGOU HUAXUE）Chinese

J.

Struct. Chem.

891

zed water and ethanol for three times, respectively.

an atmospheric fixed bed reactor. 0.1 g portion of

The final products were then dried in vacuum at 70

Pt/FeSnO(OH)5 in 30～60 mesh was filled into a

℃ for 12 h.

U-type quartz tubular reactor equipped with a

For comparison, the Pt/γ-Al2O3 catalyst (0.5 wt%

temperature-programmed controller. Gaseous ben-

Pt) was also prepared by the above method. γ-Al2O3

zene (500 ppmv, Linde Gases (xiamen) Co., Ltd.)

was obtained by Shang Dong Aluminium Industry

balanced by synthetic air (20 vol% O2 and balanced

Co., Ltd.

N2, Linde Gases (xiamen) Co., Ltd.) was fed into the

2. 3

Characterization of the Pt/FeSnO(OH)5

reactor while the total flow rate was 100 mL/min

composite catalysts

and the gas pressure maintained 0.4 MPa, correspon-

X-ray diffraction (XRD) measurements of the

ding to a gas hourly space velocity (GHSV). The

powder samples were performed on a Panalytical

catalytic activity was measured while the tempe-

X’Pert spectrometer at a scanning rate of 10 deg/min

rature was raised from 50 to 200 ℃ at a rate of 3

in the 2θ range from 10° to 90°, with Fe filter Co-Kα

℃/min and the detailed heating and cooling pro-

radiation (λ = 0.178901 nm). The infrared spectro-

cesses are shown in Fig. 1. The benzene in the

scopy (FTIR) measurements were performed with a

stream was detected by an on-line GC (Huaai,

Nicolet 5700 spectrometer. The TG-DTA measure-

GC9560) equipped with flame ionization detector

ments were performed with USA TA (SDT-Q600) at

(FID). The GC (Huaai, GC9560) was also employed

a rate of 5 ℃/min in the temperature range from 0

for the quantitative and qualitative analyses of the

to 1000 ℃ under air atmosphere. The field emis-

products and by-products. Apart from the products

sion scanning electron microscopy (FESEM) images

such as CO2 and H2O, no other by-products were

of the samples were obtained by Hitachi S4800 field

found in all of the experiments. Thus the conversion

emission scanning electron microscopy. The field

was calculated based on the benzene consumption

emission transmission electron microscopy (FETEM)

Benzene conversion (%) = [(Cinlet – Coutlet)/Cinlet] × 100

images of the samples were obtained by FEI Tecnai

where Cinlet is the concentration of compound

G2 F20 S-TWIN with a field emission gun operated

benzene at the reactor inlet and Coutlet is that at the

at 200 kV. The energy dispersive spectrometer (EDS)

reactor outlet.

data were collected using an EDAX energy disper-

For comparison, the catalytic oxidation of ben-

sive spectrometer with the FETEM. N2 adsorption-

zene by the Pt/γ-Al2O3 catalyst was carried out under

desorption analysis was measured on a Microme-

the same conditions..

ritics ASAP 2020 instrument, and the multipoint Brunauer-Emmet-Teller (BET) surface area data

3 RESULTS AND DISCUSSION

were estimated from the relative pressure ranging from 0.06 to 0.3. X-ray photoelectron spectroscopy

3. 1

Characteristics of the catalysts

(XPS) measurements were performed with an

The XRD patterns of Pt/FeSnO(OH)5 catalysts are

ESCALab250-XI electron spectrometer from VG

shown in Fig. 2, in which the XRD pattern of pure

Scientific using 300 W AlKa radiation. The base

FeSnO(OH)5 is also included for comparison. In Fig. 2

-9

mbar and the binding

(a)～(e), all the diffraction peaks can be indexed to

energies were corrected by adjusting the binding

the standard cubic phase of FeSnO(OH)5 (JCPDS

energy of the C1s peak to 284.8 eV from adventi-

31-0654) without any unindexed peaks. However, no

tious carbon.

sharp peaks for Pt can be observed, indicating that

2. 4

Catalytic oxidation measurement

the loading amount of Pt (0.5 wt%) was too low or

of the Pt/FeSnO(OH)5 composite catalysts

the Pt nanoparticles might be uniformly dispersed

Catalytic oxidation of benzene was carried out on

and their crystal sizes were very small[1]. Moreover,

pressure was about 3×10

892

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

No. 6

after the catalytic oxidation of benzene and the

talline structure of the sample was changed and

stability study at 150 and 180 ℃ for 80 h, respec-

became amorphous after the stability study at 200 ℃

tively, the crystal types of the supports did not

for 80 h (Fig. 2 (f)). Therefore, the Pt/FeSnO(OH)5

change, indicating that the Pt/FeSnO(OH)5 catalyst

catalyst can remain stable below 180 ℃.

is stable (Fig. 2(d) and (e)). Nevertheless, the crys-

Fig. 1.

Temperature-programmed pattern for the deep catalytic oxidation of benzene

Fig. 2. XRD patterns of the as-synthesized samples: (a) Pure FeSnO(OH)5; (b) and (c) Pt/FeSnO(OH)5 before and after catalytic oxidation of benzene; (d), (e) and (f) Pt/ FeSnO(OH)5 after the stability study at 150, 180 and 200 ℃ for 80 h, respectively

2016

Vol. 35

结

构

学（JIEGOU HUAXUE）Chinese

化

J.

Struct. Chem.

893

The FTIR spectra of FeSnO(OH)5 and Pt/

vibration and the H2O-H2O hydrogen binding

FeSnO(OH)5 can provide more structural and sur-

absorption were also observed at 3400, 1635 and

face information about the prepared supports, which

775 cm−1[24,

are shown in Fig. 3. IR features of the samples are

could be found at 560 cm−1 which could be assigned

similar to the reported MSn(OH)6 (M = Cu, Mg,

to the stretching modes of Sn−OH[24,

[18]

26]

, respectively. Sn involved bonds 26]

. The

−1

. Thus, the formation of as-synthesized

absorption at around 2415 cm might be assigned to

samples can be further confirmed here by the FTIR

the stretching modes of Fe−OH. However, there are

result. In Fig. 3(a)～ (e), an intense broad band

no peaks at 3200, 2415 and 1190 cm−1 in Fig. 3(f),

centers at about 3200 cm−1 together with a sharp

indicating

Zn)

−1

that

the

surface

O−H

groups

in

absorption at 1190 cm , which can be attributed to

FeSnO(OH)5 disappeared after a long time at 200 ℃.

the

in

In other words, the crystal type of the support

and the

changed after the stability study at 200 ℃ for 80 h.

, respectively.

To sum up, the Pt/FeSnO(OH)5 catalyst was stable

The rich O−H groups in FeSnO(OH)5 are beneficial

below 200 ℃, corresponding to the results of XRD

for dispersion of the Pt nanoparticles on the support

patterns in Fig. 2.

stretching

vibration

of

O−H

groups [22, 23]

FeSnO(OH)5 or surface adsorbed H2O [24, 25]

-OH bending vibration of M−OH

surface. Moreover, the OH in-plane deformation

Fig. 3.

FTIR spectra of the As-synthesized samples: (a) Pure FeSnO(OH)5; (b) and (c) Pt/ FeSnO(OH)5 before and after catalytic oxidation of benzene; (d), (e) and (f) Pt/ FeSnO(OH)5 after the stability study at 150, 180 and 200 ℃ for 80 h, respectively

The thermal decomposition properties of the

℃ due to the loss of water upon FeSnO(OH)5 de-

synthesized FeSnO(OH)5 were investigated by TGA

composition. In addition, the phase transition

and DTA and the resulted curves are shown in Fig. 4.

temperature of FeSnO(OH)5 was 220 ℃, indicating

As shown in the TGA curve, a continuous and weak

that the thermal stability and the decomposition

weight loss ca. 2wt% from room temperature to 180

temperature of FeSnO(OH)5 were higher than the

℃ was observed. It was caused by the release of

reported MSn(OH)6 (M = Zn, Cu, Mg)[22]. There was

physically adsorbed water from FeSnO(OH)5.

no doubt that higher thermal stability of FeSnO-

Further increasing the temperature, a sharp decrease

(OH)5 would be good for the catalytic oxidation of

in mass appeared at ca. 180 ℃ and ended at ca. 250

benzene.

894

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

Fig. 4.

No. 6

TGA and DTA curves of the As-synthesized FeSnO(OH)5 sample

The FESEM images of Pt/FeSnO(OH)5 are

change of FeSnO(OH)5 after the catalytic oxidation

present in Fig. 5(a～b), from which we can see that

of benzene, which is in agreement with the XRD

the samples are nanocubes with the sizes of about

data.

20～40 nm. There is no obvious morphological (b)

(a)

Fig. 5.

FESEM pictures of Pt/FeSnO(OH)5 before (a) and after (b) catalytic oxidation of benzene

of

surface area of the four samples at 160 m2/g in Table 2

Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts with their

because of the γ-Al2O3 support (159 m2/g) with a

corresponding EDS curves, respectively. The TEM

porous structure as shown in Fig. 7. Table 2 also

images and EDS curves prove that Pt nanoparticle

compared the BET surface areas of FeSnO(OH)5

was formed and attached to the FeSnO(OH)5 and

support and Pt/FeSnO(OH)5 catalyst. As presented in

γ-Al2O3 supporters, respectively, with similar size of

Table 2, the BET surface area of FeSnO(OH)5

about 5 nm.

support was 85 m2/g and that of Pt/FeSnO(OH)5

Fig.

6(a ～ d)

presents

TEM

images

Fig. 7 shows BET surface area, pore volume and

catalyst was 87 m2/g. Therefore, the negligible

size of Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts

differences between the BET surface areas indicated

measured by N2 adsorption and calculated from the

the insignificant effect of the supported Pt pro-

BET method. Pt/γ-Al2O3 exhibited the largest BET

cessing on the textural properties.

2016

Vol. 35

结

构

化

学（JIEGOU HUAXUE）Chinese

J.

Struct. Chem.

895

Table 2. BET Surface Areas, Pt Particle Size and Comparison of Conversion Temperature for Benzene Oxidation over FeSnO(OH)5, Pt/FeSnO(OH)5, γ-Al2O3 and Pt/γ-Al2O3 Catalysts at the Flow Rate of 100 mL/min (T10, T50, T90, T100, Temperature at Which the Conversion of Benzene Reached 10%, 50%, 90%, and 100%, respectively) Name

BET surface area (m2/g)

Pt particle size (nm)

T10 (℃)

T50 (℃)

T90 (℃)

T100 (℃)

FeSnO(OH)5

85

—

180

>200

>200

>200

Pt/FeSnO(OH)5

87

~5

95

120

138

160

γ-Al2O3

159

—

190

>200

>200

>200

Pt/γ-Al2O3

160

~5

100

145

158

175

Fig. 6.

FETEM pictures of (a) Pt/FeSnO(OH)5 with the corresponding EDS curve inserted, (b) Partly enlarged of (a), (c) Pt/ γ-Al2O3 with the corresponding EDS curve inserted and (d) Partly enlarged of (c)

896

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

Fig. 7.

No. 6

BET surface area, pore volume and size of Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts

XPS analyses of Pt 4d, Pt 4f, O 1s, Al 2s, Fe 2p

to Pt2+ and Pt4+ of Pt/γ-Al2O3[10].

and Sn 3d of Pt/FeSnO(OH)5 and Pt/γ-Al2O3

Fig. 8(b) shows that the O 1s peak (OI) on the

catalysts were carried out to identify the chemical

Pt/FeSnO(OH)5 catalyst appeared at 530.4 eV, which

states of the surface elements, as shown in Fig. 8. It

could be ascribed to the lattice oxygen in

0

was known that metallic Pt had relatively lower

FeSnO(OH)5. However, it was shifted to a higher BE

binding energies (BE) of 70.7～70.9 eV for 4f7/2

of about 530.8 eV for Pt/γ-Al2O3 catalyst. In addition,

and 74.0～74.1 eV for 4f5/2 electrons in Fig. 8(a),

a significant core level peak of O 1s (OII) is found at

2+

4+

and Pt oxidized states

about 531.5 and 531.9 eV for Pt/FeSnO(OH)5

exhibited much higher binding energies (72.8～73.1

catalyst, which could be ascribed to the adsorbed

respectively. However, Pt

2+

eV (4f7/2) and 76.3 ～ 76.4 eV (4f5/2) for Pt ;

oxygen. And the BE of adsorbed oxygen or

74.6～74.9 eV (4f7/2) and 78.1～78.2 eV (4f5/2) for

Pt/γ-Al2O3 catalyst appeared at 531.8 eV, while OI

4+ [1]

Pt ) . The peak of Pt 4f7/2 was concentrated upon

and OII atomic fractions of their O 1s peak were

70.2 (71.0) and the other was 73.3 (74.1) eV for the

different and Pt/FeSnO(OH)5 catalyst had higher OII

0

Pt/FeSnO(OH)5 catalyst, corresponding to Pt and 2+

atomic fraction, as shown in Table 1.

Pt , respectively. Nevertheless, it was positively

Fig. 8(c) shows that BE of Al in the Pt/γ-Al2O3

shifted to 73.7～75.3 eV for the Pt/γ-Al2O3 catalyst,

catalyst was single-peak appearing at 118.8 eV,

2+

and Pt oxidized

corresponding to Al3+ of γ-Al2O3. Sn 3d5 and Sn 3d3

states but far from the BE of metallic Pt0, indicating

for the Pt/FeSnO(OH)5 were recorded, which could

that Pt nanoparticles in Pt/γ-Al2O3 catalyst were not

be fitted by two peaks at the binding energies of

which was close to the BE of Pt

4+

0

reduced into metallic state (Pt ). This result could be

486.9 and 495.4 eV, corresponding to Sn4+ of

confirmed by Pt 4d5 and Pt 4d3 for Pt/γ-Al2O3 in Fig. 8(a)

FeSnO(OH)5[27]. Additionally, Fe 2p1 and Fe 2p3 for

which appeared at 314.3 nd 331.2 eV, corresponding

the Pt/FeSnO(OH)5 were also recorded, which could

2016

Vol. 35

结

构

化

学（JIEGOU HUAXUE）Chinese

be fitted by two peaks at the binding energies of 712.3 and 725.6 eV due to Fe

3+

of FeSnO(OH)5.

J.

Struct. Chem.

XPS data for Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts are listed in Table 1.

(a) Pt 4f Pt 4d

(b) O 1s

(c) Al 2s Fe 2p Sn 3d

Fig. 8.

897

XPS of Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts

898

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

No. 6

Table 1．XPS Data for the Pt/FeSnO(OH)5 and Pt/γ-Al2O3 Catalysts Calculated from the Corresponding Areas of Fitted Peaks Done by XPSPEAK 4.1 with Shirley Background Pt/FeSnO(OH)5

Catalyst

Atomic (%)

BE (eV)

Atomic (%)

70.2

0.06

—

—

Pt

2+

74.1

0.01

73.7

0.05

Pt

4+

Pt0 4f Pt 4d

O 1s

Fe 2p

Sn 3d Al 2s

3. 2

Pt/γ-Al2O3

BE (eV)

—

—

75.3

0.02

Pt0

—

—

—

—

Pt2+

—

—

314.3

0.05

Pt4+

—

—

331.2

0.02

OⅠ

530.4

18.10

530.8

25.82

531.5

38.50

531.8

38.22

531.9

23.79

—

—

—

—

—

—

Fe

712.3

5.87

—

—

Sn 2+

—

—

—

—

486.9

13.67

—

—

—

—

118.8

35.89

OⅡ Fe2+ 3+

Sn

4+

Catalytic oxidation of benzene

was mainly influenced by the loading amount and

To be compared with the catalytic activity of the

oxidation state of active components (Pt). Moreover,

Pt/FeSnO(OH)5 catalyst, Pt/γ-Al2O3 was used as

Table 2 and Fig. 10 present the reaction temperature

catalyst. The light-off (or ignition) and complete

of 10% (T10), 50% (T50), 90% (T90) and 100% (T100)

combustion curves were used to compare the cata-

for benzene conversion (500 ppmv in air) over

lytic activities of the catalysts for benzene oxidation.

Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts. Fig. 9

The conversion was calculated on the basis of

clearly showed the benzene comparison plot of the

benzene consumption as described in Section 2.

reaction temperature for Pt/FeSnO(OH)5 and Pt/γ-

Before conducting the complete oxidation of

Al2O3 catalysts. These results clearly supported that

benzene by Pt/FeSnO(OH)5 and Pt/γ-Al2O3 catalysts,

Pt/FeSnO(OH)5 showed better catalytic activity than

a blank test was performed to check the existence of

the Pt/γ-Al2O3 catalyst.

homogeneous reactions. The blank test detected no

To study the effects of temperature cycling, the

thermal (or homogeneous) oxidation of benzene

stability of catalytic activity of the Pt/FeSnO(OH)5

below 600 ℃ in Fig. 9, which was in agree-

catalyst was detected when the catalytic temperature

[2]

ment with the previous studies . This result

was increased and then decreased, as shown in Fig. 11.

indicated that the employed system could be applied

The results also implied a good stability of the

for analyzing the catalytic oxidation of benzene. In

Pt/FeSnO(OH)5 catalyst. No other by-products

addition, pure FeSnO(OH)5 and γ-Al2O3 showed

(benzene-derived compounds or CO) were detected

poor catalytic activity for benzene oxidation and the

according to GC except the peaks for benzene and

former exhibited slightly better catalytic activity,

CO2 at different catalytic temperature over the

indicating that the supports had only small effect on

Pt/FeSnO(OH)5 catalyst.

the removal of benzene. Compared with pure

By comparing Table 2 with Fig. 9, we can see the

FeSnO(OH)5 and γ-Al2O3, the supported Pt catalysts

catalytic activity of Pt/FeSnO(OH)5 is better than

exhibited very high catalytic activities, especially for

Pt/γ-Al2O3. Good performance of the catalyst not

the Pt/FeSnO(OH)5 catalyst. Therefore, it could be

only depends on the intrinsic properties of the active

concluded that the catalytic activity of the catalyst

metal (electronic structure, etc.), but also on its

2016

Vol. 35

结

构

化

学（JIEGOU HUAXUE）Chinese

J.

Struct. Chem.

899

crystal structure, particle size, specific surface area,

(Pt ) and 1/7 Pt exited as the oxidized forms (Pt2+).

pore structure and the dispersion states. However,

However, with the same condensation of Pt, all the

when the noble metal particles were presented in the

noble metal species exited as the oxidized forms in

form of nano-catalyst, the supported noble metal

Pt/γ-Al2O3, in which 5/7 Pt exited as Pt2+ and 2/7 Pt

catalysts exhibit a very high catalytic activity, indi-

exited as Pt4+. From above, we could conclude that

cating the performance of Pt was critical during

the metallic species were more active than their

catalysis.

of

oxidized forms for catalytic oxidation of benzene,

Pt/FeSnO(OH)5 was obviously smaller than Pt/γ-

which was in agreement with the previous resear-

Al2O3, as shown in Fig. 7, while the sizes of their

ches[1,

noble metal particles were similar, as shown in Fig. 5.

attached to both catalysts by the same method under

The most attractive difference between two catalysts

the same conditions, the difference of the Pt

was the oxidation state of Pt, as shown in Table 1. In

oxidation states could only be owed to the different

Pt/FeSnO(OH)5, 6/7 Pt exited as the reduced forms

structures of the supporters.

The

Fig. 9.

specific

surface

area

0

2]

. Considering that Pt was reduced and

Comparison plot of conversion temperatures of: (a) blank, (b) γ-Al2O3, (c) FeSnO(OH)5, (d) Pt/FeSnO(OH)5, and (e) Pt/γ-Al2O3

Fig. 10. Comparison plot of conversion temperature of T10, T50, T90 and T100 on Pt/FeSnO(OH)5 and Pt/γ-Al2O3

900

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

Fig. 11.

3. 3

No. 6

Benzene conversion versus temperature over the Pt/FeSnO(OH)5 catalyst

Stability activity tests

possible that a bit of surface O−H groups in

A long catalytic test was performed in the reactor

FeSnO(OH)5 disappeared in a long time. Therefore,

operating at constant temperature in order to inves-

the Pt/FeSnO(OH)5 catalyst was cata- lytically

tigate the stability of the Pt/FeSnO(OH)5 catalyst.

stable.

The test was detected at the condition of 95% conversion in order to observe any deactivation

4

CONCLUSION

timely, as shown in Fig. 12. In addition, the benzene conversion versus on-stream reaction time over the

In conclusion, we synthesized Pt/FeSnO(OH)5 as

Pt/FeSnO(OH)5 catalyst is also shown in Fig. 12

a novel hydroxyl catalyst. Compared with Pt/γ-Al2O3

under the conditions of reaction temperature at 150

during

℃ for 80 h and 500 ppmv benzene in air with the

Pt/FeSnO(OH)5 showed better catalytic activity.

flow rate of 100 mL/min. The percentage of con-

After characterization of the catalysts by XRD, SEM,

version was analyzed at every time interval. It was

TEM, EDS, XPS and BET, we found most Pt could

found that during 80 h on stream, no obvious

be reduced to metallic state when the hydroxyl

decrease in catalytic activity was observed, that is,

catalyst was used as supporter and the metallic state

the Pt/FeSnO(OH)5 catalyst is catalytically stable.

of Pt was more active in catalytic oxidation of

This conclusion was confirmed by the result of XRD

benzene. Pt/FeSnO(OH)5 shows good catalytic

investigation in Fig. 2(d) and FTIR spectra in Fig. 3(d).

activity and high stability, which may be a promising

Although the degree of crystallinity was sli- ghtly

catalyst. This study may also be helpful for the

decreased, no significant change in Pt/FeSnO(OH)5

design and fabrication of new catalysts.

structure and crystal phase was detected. It was

catalytic

oxidation

of

benzene,

2016

Vol. 35

结

构

化

学（JIEGOU HUAXUE）Chinese

J.

Struct. Chem.

901

Fig. 12. Stability study of Pt/ FeSnO(OH)5 catalyst at 150 ℃ for 80 h under the condition of 500 ppmv benzene in air at the flow rate of 100 mL/min

REFERENCES (1)

Li, Z. H.; Yang, K.; Liu, G.; Deng, G. F.; Li, J. Q.; Li, G.; Yue, R. L.; Yang, J.; Chen, Y. F. Effect of reduction treatment on structural properties of TiO2 supported Pt nanoparticles and their catalytic activity for benzene oxidation. Catal. Lett. 2014, 144, 1080−1087.

(2)

Shim, W. G.; Lee, J. W.; Kim, S. C. Analysis of catalytic oxidation of aromatic hydrocarbons over supported palladium catalyst with different pretreatments based on heterogeneous adsorption properties. Appl. Catal. B: Environ. 2008, 84, 133−141.

(3)

Wu, J. C. S.; Lin, Z. A.; Pan, J. W.; Rei, M. H. A novel boron nitride supported Pt catalyst for VOC incineration. Appl. Catal. A: Gen. 2001, 219, 117−124.

(4)

Giraudon, J. M.; Elhachimi, A.; Leclercq, G. Catalytic oxidation of chlorobenzene over Pd/perovskites. Appl. Catal. B: Environ. 2008, 84, 251−261.

(5)

Diehl, F.; Barbier, J.; Duprez, D.; Guibard, I.; Mabilon, G. Catalytic oxidation of heavy hydrocarbons over Pt/Al2O3: influence of the structure of the molecule on its reactivity. Appl. Catal. B: Environ. 2010, 95, 217−227.

(6)

Lin, C. A.; Wu, J. C. S.; Pan, J. W.; Yeh, C. T. Characterization of boron-nitride-supported Pt catalysts for the deep oxidation of benzene. J. Catal. 2002, 210, 39−45.

(7)

Escandón, L. S.; Ordóñez, S.; Vega, A.; Dı́ez, F. Oxidation of methane over palladium catalysts effect of the support. Chemosphere 2005, 58, 9−17.

(8)

Silviya, T.; Georgi, K.; Krasimir, T.; Yuri, K.; Vladislav, K. K. Particle size and support effects on the complete benzene oxidation by Co and Co-Pt catalysts. J. Mater. Sci. 2007, 42, 3315−3320.

(9)

Miller, J. B.; Malatpure, M. Pd catalysts for total oxidation of methane support effects. Appl. Catal. A: Gen. 2015, 495, 54−62.

(10) Corro, G.; Cano, C.; Fierro, J. L. G. A study of Pt–Pd-Al2O3 catalysts for methane oxidation resistant to deactivation by sulfur poisoning. J. Mol. Catal. A: Chem. 2010, 315, 35−42. (11) Belopukhov, E. A.; Belyi, A. S.; Smolikov, M. D.; Kir’yanov, D. I.; Gulyaeva, T. I. Benzene hydroisomerization over Pt/MOR/Al2O3 catalysts. Catal. Ind. 2012, 4, 253−260. (12) Kwon, D. K.; Seo, P. W.; Kim, G. J.; Hong, C. Characteristics of the HCHO oxidation reaction over Pt-TiO2 catalysts at room temperature: the effect of relative humidity on catalytic activity. Appl. Catal. B: Environ. 2015, 163, 436−443. (13) Huang, H. B.; Leung, D. Y. C.; Ye, D. Q. Effect of reduction treatment on structural properties of TiO2 supported Pt nanoparticles and their catalytic activity for formaldehyde oxidation. J. Mater. Chem. 2011, 21, 9647−9652. (14) Pires, J.; Carvalho, A.; Carvalho, M. B. Adsorption of volatile organic compounds in Y zeolites and pillared clays. Microporous Mesoporous Mater.

902

YU H. et al.: Pt/FeSnO(OH)5: A Novel Supported Pt Catalyst for Catalytic Oxidation of Benzene

No. 6

2001, 43, 277−287. (15) Postole, G.; Gervasini, A.; Guimon, C.; Auroux, A.; Bonnetot, B. Boron nitride supported metal catalysts: influence of the metal and preparation method. Mater. Sci. Forum. 2006, 518, 203−210. (16) Haines, B. M.; Gland, J. L. Deep oxidation of chlorobenzene on the Pt(111) surface. Surf. Sci. 2008, 602, 1892−1897. (17) Liu, C. H.; Chen, H. Y.; Ren, Z.; Dardona, S.; Piech, M.; Gao, H. Y.; Gao, P. X. Controlled synthesis and structure tunability of photocatalytically active mesoporous metal-based stannate nanostructures. Appl. Surf. Sci. 2014, 296, 53−60. (18) Fu, X. L.; Huang, D. W.; Qin, Y.; Li, L. F.; Jiang, X. L.; Chen, S. F. Effects of preparation method on the microstructure and photocatalytic performance of ZnSn(OH)6. Appl. Catal. B: Environ. 2014, 148, 532−542. (19) Fu, X. L.; Wang, X. X.; Ding, Z. X.; Leung, D. Y. C.; Zhang, Z. Z.; Long, J. L.; Zhang, W. X.; Li, Z. H.; Fu, X. Z. Hydroxide ZnSn(OH)6: a promising new photocatalyst for benzene degradation. Appl. Catal. B: Environ. 2009, 91, 67−72. (20) Wang, Z. J.; Liu, J.; Wang, F.; Chen, S. Y.; Luo, H.; Yu, X. B. Size-controlled synthesis of ZnSnO3 cubic crystallites at low temperatures and their HCHO-Sensing properties. J. Phys. Chem. C 2010, 114, 13577−13582. (21) Jiang, H.; Geng, B. Y.; Kuai, L.; Wang, S. Z. Simultaneous reduction-etching route to Pt/ZnSnO3 hollow polyhedral architectures for methanol electrooxidation in alkaline media with superior performance. Chem. Commun. 2011, 47, 2447−2449. (22) Jena, H.; Kutty, K. V. G.; Kutty, T. R. N. Ionic transport and structural investigations on MSn(OH)6 (M = Ba, Ca, Mg, Co, Zn, Fe, Mn) hydroxide perovskites synthesized by wet sonochemical methods. Mater. Chem. Phys. 2004, 88, 167−179. (23) Kramer, J. W.; Isaacs, S. A.; Manivannan, V. Microwave-assisted metathesis synthesis of Schoenfliesite-type MSn(OH)6 (M = Mg, Ca, Zn, and Sr) materials. J. Mater. Sci. 2009, 44, 3387−3392. (24) Zhong, S.; Xu, R.; Wang, L.; Xu, H. F.; Zhong, S. L. CuSn(OH)6 submicrospheres: room-temperature synthesis, growth mechanism,and weak antiferromagnetic behavior. Mater. Res. Bull. 2011, 46, 2385−2391. (25) Velu, S.; Suzuki, K.; Okazaki, M.; Osaki, T.; Tomura, S.; Ohashi, F. Synthesis of new Sn-incorporated layered double hydroxides and their thermal evolution to mixed oxides. Chem. Mater. 1999, 11, 2163−2172. (26) Pramanik, N. C.; Das, S.; Biswas, P. K. The effect of Sn(IV) on transformation of co-precipitated hydrated In(III) and Sn(IV) hydroxides to indium tin oxide (ITO) powder. Mater. Lett. 2002, 56, 671−679. (27) Han, L. X.; Liu, J.; Wang, Z. J.; Zhang, H.; Luo, H.; Xu, B.; Zou, X.; Zheng, X.; Ye, B.; Yu, X. B. Shape-controlled synthesis of ZnSn(OH)6 crystallites and their HCHO-sensing properties. CrystEngComm. 2012, 14, 3380−3386.