Catalytic hydrodechlorination of 1,2,4,5-tetrachlorobenzene over various supports loaded palladium catalysts

Article abstract of DOI:10.1002/jccs.201400233

Water pollution by polychlorinated aromatic hydrocarbons has always been a global issue. In this work, we reported a synthesis of supported palladium catalysts Pd/C, Pd/CeO₂, Pd/SBA-15, Pd/ZrO₂, Pd/SiO₂, and Pd/Al₂O₃ as well as their catalytic activities on hydrodechlorination (HDC) of 1,2,4,5-tetrachlorobenzene (TeCB). These Pd catalysts were characterized by Brunauer-Emmett-Teller (BET) specific surface area, Transmission electron microscopy (TEM), X-ray diffraction (XRD), energy Dispersive X-ray Fluorescence (EDXRF), CO-chemisorption, and H₂-temperature programmed reduction (H₂-TPR) analysis. Pd/C, Pd/CeO₂ and Pd/SBA-15 catalysts showed relatively high catalytic activities. The catalytic activities were associated with dispersion of Pd, metal surface area, and reaction temperature, etc.

Full text of DOI:10.1002/jccs.201400233

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Catalytic Hydrodechlorination of 1,2,4,5-Tetrachlorobenzene over Various Supports
Loaded Palladium Catalysts
a
b,
a
a
a,
Yue-Hui Fan, Li-Rong Zhang, * Guan-Lin Zhang, Hu Xu, Yu-Hong Wang * and
a
aGuan-Zhong Lu
Research Institute of Applied Catalysis, School of Chemical and Environmental Engineering, Shanghai Institute of
Technology, Shanghai 201418, P. R. China
b
School of Perfume and Aroma Technology, Shanghai Institute of Technology, Shanghai 201418, P. R. China
(Received: May 23, 2014; Accepted: Sept. 11, 2014; Published Online: Nov. 11, 2014; DOI: 10.1002/jccs.201400233)
Water pollution by polychlorinated aromatic hydrocarbons has always been a global issue. In this work,
we reported a synthesis of supported palladium catalysts Pd/C, Pd/CeO
2 2 2
, Pd/SBA-15, Pd/ZrO , Pd/SiO ,
and Pd/Al as well as their catalytic activities on hydrodechlorination (HDC) of 1,2,4,5-tetrachloro-
2
O
3
benzene (TeCB). These Pd catalysts were characterized by Brunauer-Emmett-Teller (BET) specific sur-
face area, Transmission electron microscopy (TEM), X-ray diffraction (XRD), energy Dispersive X-ray
Fluorescence (EDXRF), CO-chemisorption, and H
2 2
-temperature programmed reduction (H -TPR) analy-
sis. Pd/C, Pd/CeO and Pd/SBA-15 catalysts showed relatively high catalytic activities. The catalytic ac-
2
tivities were associated with dispersion of Pd, metal surface area, and reaction temperature, etc.
Keywords: Supported Pd catalysts; Catalytic hydrodechlorination; 1,2,4,5-Tetrachlorobenzene.
INTRODUCTION
Polychlorinated aromatic hydrocarbons (PCAH) are
port, metal particle size, reaction media, and reaction con-
7
ditions. Shao et al. compared the catalytic behavior of
considered as the hazardous pollutants due to their acute
Pd/ZrO
found that catalysts with high Pd specific surface area and
surface hydroxyl group content in ZrO support exhibited a
higher initial activity and stability. Gómez-Quero et al.
investigated the effect of metal particle size on liquid-phase
HDC of 2,4-dichlorophenol over Pd/Al catalysts and
2
for gas phase HDC of chlorobenzene (CB) and
1
toxicity and high bioaccumulation potential. With the
ever-increasing concerns for environmental protection and
human health, the safe disposal of PCAH has attracted
2
2
6
2
,3
much attention. Various methods such as incineration and
thermal oxidation were carried out to degrade the PCAH.
However, incomplete oxidation usually leads to the forma-
tion of more toxic species such as dioxins, phosgene and
2
O
3
found smaller particles (< 5 nm) possessed a higher activity.
As a member of PCAH family, 1,2,4,5-tetrachloro-
benzene (TeCB) is one of 31 priority chemicals targeted by
the United States Environmental Protection Agency for
4
chlorine etc. In contrast, catalytic hydrodechlorination
(
HDC) may become a promising method, by which PCAH
5
27
can be converted into various valuable products. Further-
more, this reaction can be effectively carried out at room
temperature and atmospheric pressure. Catalytic HDC can
be conducted in both liquid and vapor phase using noble
waste reduction. The potential hazard of TeCB for human
being possibly stemmed from the damage on liver, kidney,
2
8
and thyroid. However, the HDC of TeCB by the sup-
ported Pd catalysts in liquid phase has been rarely studied.
6
-14
15,16
17
18,19
29
metal (Pd,
Pt,
Ru, Rh
) or non-noble metal
2 3
Wee reported that the HDC of TeCB by Pd/Al O in wa-
6
,20
21,22
23,24
(
Ni, Ni-Mo,
Fe
) as catalysts. Among all Group
ter-ethanol mixtures and TeCB was converted rapidly and
quantitatively into benzene. The impact of Pd catalysts
loaded on different type supports has seldom been ad-
dressed, which promotes us to study the effects of different
supports loaded Pd catalysts on HDC of TeCB in liquid
phase. In this work, we described the preparation of various
VIII metal catalysts, Pd is considered as the most effective
catalyst for liquid phase HDC since it can selectively re-
2
3,25
place the chlorine element of substrate with hydrogen.
These metal catalysts for HDC are usually loaded on vari-
1
1,15,17
13,17,20
17,20
ous supports including carbon,
Al
etc. The catalytic activity of
catalysts is significantly dependent on the nature of sup-
2
O
3
,
2
SiO ,
2
0
7,17
14,17
MgO, ZrO
2
,
and CeO
2
,
2
supports loaded Pd catalysts Pd/C, Pd/CeO , Pd/SBA-15,
Pd/ZrO
2
, Pd/SiO
2
, and Pd/Al
2
O
3
and evaluated their cata-
*
Corresponding author. E-mail: zlir2008@163.com (L. R. Zhang); yuhong_wang502@sit.edu.cn (Y. H. Wang)
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Fan et al.
3
2-34
35
lytic activities on HDC of TeCB at room temperature
catalytic activities.
Gopinath et al. investigated the HDC re-
(
Scheme I). The experimental results implied that the cata-
action on supported Pd catalysts and found that catalyst with 1
wt% Pd was more active and stable compared with traditional 10
wt% Pd catalysts. Considering the above finding, we decided to
utilize 3 wt% Pd loading on various supports in this study. The Pd
catalysts were prepared through an impregnation-deposition
lytic HDC activity of Pd catalysts was significantly de-
pendent on the metal surface area, metal dispersion, and
reaction temperature, etc. The product distribution was
also discussed.
method with g-Al
carbon as different supports, respectively. Typically, the PdCl
0.1 g) aqueous solution (5 mL) was added to a support suspen-
2 3 2 2 2
O , CeO , ZrO , SiO , SBA-15, and activated
Scheme I The illustration of HDC of TeCB by various
2
supported Pd catalysts
(
sion (2.0 g of support in 100 mL of deionized water) under stir-
ring. The suspension pH value was adjusted to 8.5 by adding 1 M
of NaHCO
3
solution and was maintained for 1.5 h during precipi-
tation. Then a formaldehyde aqueous solution (37 wt%, 20 mL)
3
6
was added to reduce Pd from Pd(II) to Pd(0). After the reaction,
the filter cake was collected by filtration and washed with deion-
ized water followed by ethanol to remove excess chloride ions
and dried open to air overnight at 353 K to get 3 wt% Pd catalysts.
EXPERIMENTAL
2
Surface area and pore volume: N adsorption-desorption
General: ZrO
ports were obtained from Adamas. PdCl
Al , and other traditional chemicals were purchased from
Sinopharm Chemical Reagent Company. SiO
ports were prepared according to the previously described meth-
ods. N adsorption-desorption isotherms were obtained on a
2
, SBA-15, and activated carbon used as sup-
isotherms were obtained at 77 K after all samples were degassed
under vacuum at 473 K for 3 h. BET surface areas were calculated
from the linear part of the BET plot.
2
, cerium (III) nitrate, g-
2
O
3
3
0
31
2
and CeO
2
sup-
Transmission electron microscopy (TEM): The catalyst
sample was dispersed in ethanol by ultrasonic vibration, depos-
ited on a lacey-carbon/Cu grid. For estimation of particle size, at
least more than 100 individual particles were counted for each
catalyst. The mean metal particle size was calculated as the sur-
face-area-weighted average size (d) according to the following
expression:
2
Micromeritics ASAP 2020M+C adsorption apparatus. The Pd
content in supported catalysts was determined by Energy
Dispersive X-ray Fluorescence (EDXRF, Skyray, 4500H). Trans-
mission electron microscopy (TEM) investigations were per-
formed with an FEI Tecnai G2 20 microscope operated at 200 kV.
Room temperature XRD patterns were collected using a Philips
X’Pert PRO powder diffractometer using a copper long fine focus
X-ray diffraction tube operating at 40 kV and 40 mA as X-ray
source. The intensity data were obtained in the 2q range from 10°
3
åi nidi
d =
2
i
nid
åi
where n
These data were reported at 95% confidence interval.
Temperature-programmed reduction (TPR): Typically,
0.1 g of the as-prepared Pd catalyst was pretreated at 523 K in N
(mass flow controlled at 50 mL/min) for 2 h prior to a TPR mea-
surement. For TPR experiment, H /N gas (v/v = 1:9) with the rate
i i i
is the number of particles of diameter d , and Sn >100.
to 80° with a scan rate of 0.1°/s. H
2
-temperature-programmed re-
duction (H -TPR) was performed using a continuous-flow appa-
2
ratus equipped with a thermal conductivity detector (TCD).
CO-chemisorption measurements were carried out on Auto Chem
2
2
910 (Micromeritics, USA) instrument. Catalytic HDC activity
2
2
of Pd catalysts was evaluated by gas chromatograph (GC-9790,
Fuli, MD) equipped with a flame ionization detector (FID), a
of 50 mL/min was used and the temperature was ramped from
room temperature to 873 K at 10 K/min while the effluent gas was
analyzed with a TCD.
PEG-20M capillary column (30 m × 0.25 mm × 0.5 µm), and N
2
as carrier gas. The initial oven temperature was set at 50 °C for 3
min, and then was raised with a gradient of 10 °C/min until 200 °C
and was held for 5 min. The temperature of the FID and the injec-
tion was 250 °C.
Pulse CO chemisorption: Prior to adsorption measure-
2
ments, 0.1 g of Pd catalyst was firstly reduced in a H flow (50
mL/min) at 573 K for 2 h and subsequently gas flow was changed
to pure He flow at 573 K for 1 h. Then the sample was cooled
down to room temperature in He stream. Then CO uptake was de-
termined by injecting pulses of 10% CO balanced He from a cali-
Preparation of Pd catalysts: It was reported that catalysts
with low Pd loading on supports (5-10%) preferred to gain high
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Catalyzed Hydrodechlorination of Chlorobenzene
brated on-line sampling valve into the He stream passing through
the Pd catalyst system. Palladium surface area, dispersion per-
centage, and Pd average particle size were calculated by assum-
ing the stoichiometric factor (CO/Pd (S)) as 1. Adsorption was
deemed to be complete after three successive runs showed similar
peak areas.
ing the following equation assuming the spherical particle
exposed to the gas plane was also shown in Table 1.
The % Dispersion = (number of surface Pd atoms) /
(total number of Pd atoms) × 100%. The palladium metal
areas were calculated from CO consumption using the rela-
tionship S Pd = (n ´ N ´ d)/(W ´ P), where nco is the CO
co
A
Catalytic activity: The HDC reactions were carried out at
consumption, N
tional area of the Pd atom, i.e. 8.33 Å . One way the Pd par-
ticle size (d , nm) was calculated from the estimated metal
surface area (SPd) according to
where r is the density of Pd metal, i.e. 12.02 g×cm , an-
other method the Pd particle size (d , nm) was calculated by
TEM measurements. The results shown in Table 1 indi-
cated that Pd/C, Pd/CeO , and Pd/SBA-15 Pd catalysts ex-
A
is avogadro constant, d is the cross-sec-
2
2
98 K. Typically, a suspension containing one certain supported
Pd catalyst (0.1 g), TeCB (0.1 g), and 100 mL of methanol/water
v/v = 1:9) was stirred for 20 min to reach the adsorption equilib-
rium between TeCB and Pd catalyst surface, after that the reactor
was purged with pure H three times and the H atmosphere in re-
1
3
7
(
1
d = 60000 / (r × SPd),
-
3
2
2
2
actor was maintained at standard atmosphere pressure. Then the
HDC reaction started counting and aliquots of sample were taken
at different time intervals for GC analysis. Usually, the HDC reac-
tions were quenched within 10 h.
2
hibited the high Pd dispersion (over 44%) suggesting a ho-
mogeneous distribution of active component on the corre-
sponding supports compared with other catalyst systems.
Generally, Pd dispersion decreased with the increase in
RESULTS AND DISCUSSION
11
The characterization of supported Pd catalysts
particle size, which was in good accord with the observa-
tion in present study. The higher CO-uptake values for
All the as-prepared supported Pd catalysts were
firstly characterized by XRD analysis. However, no evi-
dent difference was observed in the powder XRD patterns
between Pd/support and corresponding support possibly
due to the relatively low Pd loading (3 wt%). Through
transmission electron microscopy, we determined the pres-
ence of Pd (Fig. 1) and calculated palladium particle size.
In order to verify the existence of Pd in catalyst systems, we
performed the Pd content analysis by EDXRF technique
and obtained a Pd content range from 1.9 to 2.3 wt%. The
Pd content in all catalyst systems was smaller than 3 wt%
stated above, which could result from the inadequate ad-
sorption in reaction process. Nevertheless, the successful
Pd loading in various supported Pd systems was quite obvi-
ous. The different supports-loaded Pd catalysts were also
characterized by Brunauer-Emmett-Teller (BET) surface
area analysis, particle size determination, and CO-chemi-
sorption analysis and the results were comprised in Table 1.
The Pd dispersion calculated from CO-chemisorption us-
2
Pd/C, Pd/CeO , and Pd/SBA-15 suggested that Pd particles
were dispersed well on the corresponding support.
Temperature programmed reduction (TPR) was per-
formed to provide necessary information about the nature
of reduced Pd species in various supported Pd catalysts
(Fig. 2). For all supported Pd catalyst systems, the absence
of the negative peak in temperature range from 323 to 348
K implied the absence of b-PdH, which was usually
3
8
formed in the presence of larger Pd particles. This obser-
vation indicated the existence of smaller Pd particles in our
catalyst systems (< 6 nm). All supported Pd catalysts ex-
hibited a similar positive reduction peak at 378~385 K,
which could be attributed to the reduction of support-inter-
Fig. 1. TEM micrographs of Pd/C, Pd/CeO
SBA-15.
2
, and Pd/
Fig. 2. TPR profiles of various supported Pd catalysts.
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Fan et al.
Table 1. Physico-chemical properties of various supported Pd catalysts
S • TOF ×
Particle size (nm)
-5
Pd
Actual Pd
loading (wt%) area (m /g)
BET Surface
CO uptake
(ìmol/g)
Dispersion
(%)
2
-1
TOF × 10
-
3
2
-1
Catalysts
SPd (m • g )
10 (m • g •
2
-1
a
b
(s )
-1
d1
d2
s )
Pd/C
2.3
2.0
2.3
1.9
2.3
2.0
619.6
421.2
82.2
439.3
23.2
129
103
97
75
60
59.7
54.8
44.9
42.0
27.8
22.3
2813.6
224.6
211.5
163.5
130.8
91.6
1.8
2.2
2.4
3.1
3.8
5.5
2.2
2.5
2.6
3.6
4.0
5.9
1.7
1.9
2.2
2.3
2.5
3.0
4.8
4.2
4.6
3.7
3.2
2.7
Pd/SBA-15
Pd/CeO2
Pd/SiO2
Pd/ZrO2
Pd/Al O
129.4
42
2
3
a
b
d1: Particle size measured by CO chemsiorption. d2: Particle size calculated by TEM measurements.
3
9
acted PdO species. As for Pd/C and Pd/CeO
duction peak in high temperature range (> 600 K) was ob-
served. It is rarely reported that PdO cannot be reduced at
a temperature as high as 750 K. Thus, the peaks of Pd/CeO
at about 750 K could be associated with the partial reduc-
tion of CeO support, while the high temperature reduction
peaks of Pd/C might be related to the reduction of some
PdCl or Pd(OH)Cl that were not fully reduced by formal-
2
, a broad re-
catalysts decreased in different extent. Pd/C catalyst exhib-
ited the best catalytic performance, for example, over 70%
of TeCB was converted in the initial 2.5 h. In the subse-
quent 7.5 h of reaction, TeCB was continuously degraded
and the final concentration was less than 5%. Pd/SBA-15
x
2
2
2
and Pd/CeO exhibited the similar catalytic behavior to
Pd/C but with lower catalytic activities. The residual TeCB
concentrations in these two cases were 16% and 9% after
2
dehyde or not washed away during preparation.
10 h of reaction, respectively. Pd/SiO
ZrO showed the worse catalytic activities and more than
40% of substrate was still remained even after 10h. In gen-
eral, Pd/C, Pd/CeO , and Pd/SBA-15 catalysts exhibited
2 2 3
, Pd/Al O , and Pd/
Catalytic activity
2
The catalytic activity of the supported Pd catalysts
was investigated by the HDC of TeCB at 298 K. The prod-
ucts in all HDC reactions included main product benzene
together with a small amount of chlorobenzene (CB), di-
chlorobenzene (DCB), and trichlorobenzene (TCB) as de-
termined by GC analysis. Fig. 3 showed the continuous
concentration change of TeCB against reaction time over
supported Pd catalysts. Initially, all Pd catalysts exhibited
an appreciable catalytic activity. However, with the exten-
sion of reaction time, the catalytic activities of different Pd
2
relatively high catalytic HDC activities, which could be at-
tributed to the high Pd dispersion (44.9-59.7%) and high
2
metal surface area (211.5-281.3 m /g) that could provide
more active sites for substrate accessibility. While the rela-
tively low catalytic HDC activities exhibited over Pd/SiO
2
,
Pd/Al , and Pd/ZrO could be due to the low Pd disper-
2
O
3
2
sion and low Pd surface area (Table 1). On the other hand,
as shown in Fig. 3, the gradually declined TeCB concentra-
tion lines were indicative of the catalyst deactivation dur-
ing HDC process. The reaction solution (Pd/C as catalyst)
pH is 6.25 before the experiment and down to 1.82. The de-
activation of Pd catalysts generally originated from HCl
formed during reaction, which increased the acidity of the
catalysts and leaded to the poisoning of catalysts. Some au-
thors have reported that C and SBA-15, as supports com-
2 2 2 3
pared to other supports (SiO , ZrO , Al O ) owing to their
high surface area and pore size distribution which can ab-
sorb the formed HCl, show resistance to severe deactiva-
1
7
tion. In a word, the overall catalytic properties of vari-
ous supported Pd catalysts in present study were greatly
dependent on Pd metal dispersion, metal surface area, and
the deactivation, where as independence with the property
of supports.
Fig. 3. Activity profiles of various supported Pd cata-
lysts.
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Catalyzed Hydrodechlorination of Chlorobenzene
To better understand the nature of the activity of the
catalyst active sites, the TeCB HDC activity of the reaction
was expressed in terms of turn-over frequency (TOF)
which is defined as the number of TeCB molecules de-
graded per atom of exposed palladium on the surface per
unit time. The results in Fig. 3 showed that the reactant con-
version is more than 50% after 5h of reaction. To appropri-
ately compare the activity of the active sites of different
catalysts in the kinetic region, the TOFs were calculated on
the basis of formed TeCB after 15 min of reaction (the data
during the initial 15 min), and the results are listed in Ta-
ble 1.
Herein, the Pd/C catalyst is the most efficient for the
-
5
TeCB HDC, but its TOF is only 1.7 × 10 . This is because
the activity of the Pd catalyst is not only related to the cata-
lytic activity of the individual Pd atoms (TOF) but also to
the total number of Pd atoms on the catalyst surface,
0
namely, the surface area of Pd (SPd) on the catalyst. The
larger the SPd is, the greater the number of active sites on the
catalyst surface is. If the SPd·TOF values of catalysts were
compared, we found that SPd·TOF of the Pd/C catalyst is the
-
3
2
-1 -1
largest (4.8 × 10 m s g ) among all of the Pd catalysts
(Table 1).
Effect of temperature and kinetic analysis
Fig. 4 showed the relationship between TOF and the
In order to investigate the effect of reaction tempera-
ture on the HDC of TeCB, we performed the HDC reaction
catalyzed by Pd/C at 293, 303, 313, and 323 K respectively,
and the result was illustrated by plotting the conversion of
TeCB against reaction time (Fig. 6). Under the four differ-
ent temperature conditions, benzene was always formed as
the major product together with a small amount of CB,
DCB, and TCB as by-products. Repeated experiments gave
the similar results showing the considerable reproduci-
bility. For all cases, TeCB conversion always went up with
time extension but the growing rate of conversion de-
creased with the prolonging of reaction time. Generally, in-
creasing temperature is beneficial for chemical reactions.
The catalytic HDC of TeCB in the present study was in ac-
cord with this rule. As for the reaction temperature we stud-
ied, high temperature always provided the higher TeCB
conversion than those obtained at lower temperature under
mean particle size of Pd (d
sorption. The results show that the TOF value increases
with an increase in d , that is to say, the larger Pd particles
1
) calculated from CO-chemi-
1
possess higher initial catalytic activities for the title reac-
tion because the smaller Pd particles exhibit stronger inter-
action with support. This situation has been found in the
2 4 2
Pd/SiO /AlPO , Pd/ZrO and Pd/MgO catalyst for bromo-
3
2
benzene HDC to benzene and indicates also the struc-
ture-sensitive catalytic hydrogenation character of the title
reaction. The similar phenomenon was also observed in the
1
7
previous report.
TOF against the metallic Pd surface area (SPd) was
plotted in Fig. 5. The results show that TOF of TeCB de-
crease with an increase in SPd, which indicates a decrease in
utilization of individual Pd atoms. This result suggests that
the activity of the catalyst is not only related to SPd but also
to other causes.
0
the same reaction conditions. By plotting ln(c /c) against
Fig. 4. The relationship between particle size and TOF
for TeCB HDC over various supported Pd cata-
lysts.
Fig. 5. The relationship between metal surface area
and TOF for TeCB HDC over various sup-
ported Pd catalysts.
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Fan et al.
Table 2. Rate constants (k) values for HDC of TeCB at different
reaction temperatures
Temperature The first order reaction rate
-1
2
k (h )
R
(K)
equation
2
3
3
3
93
03
13
23
ln(c /c) = 0.9469t + 0.0083
0.9469 0.9937
1.9973 0.9928
2.7595 0.9904
3.5694 0.9920
0
ln(c /c) = 1.9973t + 0.0133
0
ln(c /c) = 2.7595t - 0.3407
0
ln(c /c) = 3.5694t - 0.7940
0
reaction time (t), we got a straight line showing a first or-
der feature for the catalytic HDC of TeCB, which was sim-
2
9
ilar to the previous result. From the lines in Fig. 6 and
ln(c /c) = kt, we had calculated the values of rate constant
0
k that were listed in Table 2. With higher reaction temper-
ature, k corresponded to a larger value showing the de-
pendence of reaction rate on reaction temperature. From
Arrhenius equation, the overall apparent activation en-
ergy in the range 293-323 K was estimated to be 34.1 kJ/
mol.
Product distribution and possible reaction path
Fig. 7a shows the product distribution obtained by
Pd/C catalyst at 303 K as a function of reaction time. As ex-
pected, benzene, the main product, appeared at the begin-
ning of the reaction and its yield increased linearly with
time, showing that benzene was considerably stable and
could not be further degraded under the reaction condi-
tions. Other products including CB, p-DCB, and o-DCB
were always present in the reaction mixture and their yields
gradually increased but their contents were relatively low
Fig. 7. Product yields of TeCB (a) and TCB (b) as a
function of time at 303 K using Pd/C as cata-
lyst. On the left: benzene. On the right: CB,
p-DCB, o-DCB, and TCB (TCB was only pres-
ent in Fig. 7a).
(
< 6%). For TCB, it appeared from the beginning of the re-
reaction time and then declined near to zero. This phenom-
enon implied that TCB would be a reaction intermediate,
which was further converted into other products in later
stage. A similar product distribution profile as Fig. 7a was
also obtained at other studied temperatures. In order to de-
termine whether TCB was the intermediate, we studied the
reactivity of TCB under the same conditions (Fig. 7b). The
result indicated that TCB was an intermediate in HDC of
TeCB because of the quantitative conversion to benzene.
Interestingly, the possible products such as m-DCB, cyclo-
hexane, or chlorocyclohexane were not monitored
throughout our experiments using TeCB or TCB as sub-
strates. The possible reasons could be ascribed to the in-
action, but its yield passed through a maximum at 1.5 h of
4
0
ductive and steric effects. The similar phenomenon was
4
1
also observed in previous report. Based on the above
results, we supposed the possible main reaction path of
HDC of TeCB (Scheme II).
Fig. 6. Temporal TeCB conversion profiles at 293,
03, 313, and 323 K using Pd/C as catalyst.
3
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Catalyzed Hydrodechlorination of Chlorobenzene
Scheme II The possible main reaction path of HDC of
12. Hildebrand, H.; Mackenzie, K.; Kopinke, F. D. Environ. Sci.
Tech. 2009, 43, 3254.
TeCB by Pd catalysts in this study
1
1
1
1
3. Kumar, J. V.; Lingaiah, N.; Babu, N. S.; Kumar, V. P.; Prasad,
P. S. Catal. Lett. 2009, 132, 109.
4. Gopinatha, R.; Lingaiaha, N.; Sreedhar, B. Appl. Catal. B.
2
003, 46, 587.
5. Yoneda, T.; Takido, T.; Konuma, K. J. Mol. Catal. 2007, 265,
0.
8
6. Bonarowska, M.; Kaszkur, Z.; K“pi½ski, L.; Karpi½ski, Z.
Appl. Catal. B. 2010, 99, 248.
CONCLUSIONS
17. Srikanth, C. S.; Kumar, V. P.; Viswanadham, B.; Chary, K. V.
R. Catal. Commun. 2011, 13, 69.
In this work, we investigated the catalytic activities of
SiO
2
, g-Al
2
O
3
, CeO
2
, activated carbon, ZrO
2
, and SBA-15
18. Benítez, J. L.; Angel, G. D. Ind. Eng. Chem. Res. 2010, 50,
2
678.
supported Pd catalysts for HDC of TeCB and found that
different supports loaded Pd catalysts exhibited different
catalytic HDC activities. Without consideration of support
properties, the overall catalytic HDC activities of various
supported Pd catalysts were greatly dependent on metal
dispersion, metal surface area, metal particle size, and
reaction temperature.
1
9. Diaz, E.; Mohedano, A. F.; Casas, J. A.; Calvo, L.; Giarranz,
M. A.; Rodriguez, J. J. Appl. Catal. B. 2011, 106, 469.
0. Keane, M. A.; Larsson, R. Catal. Commun. 2008, 9, 333.
1. Gryglewicz, S.; Piechocki, W. Chemosphere 2011, 83, 334.
2. Gryglewicz, G.; Stolarski, M.; Gryglewicz, S.; Gryglewics,
S.; Klijanienko, A.; Piechocki, W.; Hoste, S.; Driessche, I.
V.; Carleer, R.; Yperman, J. Chemosphere 2006, 62, 135.
3. Munoz, M.; de Pedro, Z. M.; Casas, J. A.; Rodriguez, J. J.
Water. Res. 2013, 47, 3070.
2
2
2
2
ACKNOWLEDGEMENTS
We thank the Shanghai Municipal Natural Science
Key Research Project of China (No. J51503) and Shanghai
Municipal Natural Science Foundation of China (No.
24. Aristov, N.; Habekost, A. Chemosphere 2010, 80, 113.
25. Coq, B.; Ferrat, G.; Figueras, F. J. Catal. 1986, 101, 434.
2
6. Gómez-Quero, S.; Cárdenas-Lizana, F.; Keane, M. A. Ind.
Eng. Chem. Res. 2008, 47, 6841.
11YZ221) for financial support.
2
7. U.S. Environmental Protection Agency. Priority Chemicals
and Fact Sheets; http://www.epa.gov/epaoswer/hazwaste/
minimize/chemlist.htm (Accessed August 2010).
8. den Besten, C.; Vet, J. J. R. M.; Besselink, H. T.; Kiel, G. S.;
Berkel, B. J. M.; Beens, R.; Bladeren, P. J. Toxicol. Appl.
Pharm. 1991, 111, 69.
REFERENCES
1
2
3
4
5
6
7
8
9
. „vanꢀarová, M.; KÍesinová, Z.; Cajthaml, T. J. Hazard. Ma-
2
ter. 2013, 254, 116.
. Morra, M. J.; Borek, V.; Koolpe, J. J. Environ. Qual. 2000,
2
9, 706.
. Alonso, F.; Beletskaya, I. P.; Yus, M. Chem. Rev. 2002, 102,
009.
2
3
9. Wee, H. Y.; Cunningham, J. A. J. Hazard. Mater. 2008, 155,
1
.
4
0. Shen, S. D.; Gu, T.; Mao, D. S.; Xiao, X. Z.; Yuan, P.; Yu, M.
H.; Xia, L. Y. Chem. Mater. 2011, 24, 230.
. Erickson, M. D.; Swanson, S. E.; Flora, J. J. D.; Hinshaw, G.
D. Environ. Sci. Tech. 1989, 23, 462.
3
3
1. Feng, T.; Wang, X.; Feng, G. Mater. Lett. 2013, 100. 36.
2. AramendRa, M. A.; Boráu, V.; GarcRa, I. M.; Jiménez, C.;
Lafont, F.; Marinas, A.; Marinas, J. M.; Urbano, F. J. J.
Catal. 1999, 187, 392.
. Gaddalla, M. A.; Sommer, M. E. Chem. Eng. Sci. 1989, 44,
2
825.
. Amorim, C.; Wang, X.; Keane, M. A. Chin. J. Catal. 2011,
2, 746.
3
3
3
3
3
3
3. Gopinath, R.; Lingaiah, N.; Suryanarayana, I.; Sai Prasad, P.
. Shao, Y.; Xu, Z. Y.; Wan, H. Q.; Chen, H.; Liu, F. L.; Li, L.
Y.; Zheng, S. R. J. Hazard. Mater. 2010, 179, 135.
. Kawabata, T.; Atake, I.; Ohishi, Y.; Shishido, T.; Tian, Y.;
Takaki, K.; Takehira, K. Appl. Catal. B. 2006, 66, 151.
. Meng, B. C.; Sun, Z. Y.; Ma, J. P.; Cao, G. P.; Yuan, W. K.
Catal. Lett. 2010, 138, 68.
S. React. Kinet. Catal. Lett. 2003, 79, 61.
4. Berry, F. J.; Smart, L. E.; Sai Prasad, P. S.; Lingaiah, N.; Rao,
P. K. Appl. Catal. A. 2000, 204, 191.
5. Gopinath, R.; Babu, N. S.; Kumar, J. V.; Lingaiah, N.;
Prasad, P. S. S. Catal. Lett. 2008, 120, 312.
6. Jin, Z. H.; Li, D.; Wang, X. Y.; Lu, G. Z. Chin. J. Chem. 2010,
1
0. Nakao, R.; Rhee, H.; Uozumi, Y. Org. Lett. 2005, 7, 163.
1. Calvo, L.; Gilarranz, M. A.; Casas, J. A.; Mohedano, A. F.;
Rodríguez, J. J. Appl. Catal. B. 2006, 67, 68.
2
8, 16.
1
7. Anderson, J. R. Structure and Metallic Catalysis; Academic
J. Chin. Chem. Soc. 2015, 62, 117-124
© 2015 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.jccs.wiley-vch.de
123

Article
Fan et al.
Press: London, 1975; p 296.
8. Chang, T. C.; Chen, J. J.; Yeh, C. T. J. Catal. 1985, 96, 51.
Gomez, R., Ed.; Iberoamericano de Catalisis Guanajuato
Mexico, 1988; p 1145.
3
3
9. Babu, N. S.; Lingaiah, N.; Gopinath, R.; Reddy, P. S. S.;
Prasad, P. S. S. J. Phys. Chem. C 2007, 111, 6447.
41. Meshesha, B. T.; Chimentão, R. J.; Medina, F.; Sueiras, J. E.;
Cesteros, Y.; Salagre, P.; Figueras, F. Appl. Catal. B 2009,
87, 70.
4
0. Coq, B.; Figueras, F.; Bodnariuk, P.; Cossio, F.; Bermudez,
O.; del Angel, G. In Proceedings of the XI Symposium;
124
www.jccs.wiley-vch.de
© 2015 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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