Catalytic hydrodechlorination of 4-chlorophenol over a series of Pd-Cu/γ-Al2O3 bimetallic catalysts

Article abstract of DOI:10.1039/c4ra10798e

A series of Pd-Cu/γ-Al₂O₃ bimetallic catalysts was prepared using the sequentially incipient wetness impregnation method. The catalysts were characterized using X-ray diffraction, temperature programmed reduction, scanning electron microscopy-energy dispersive X-ray, and hydrogen (H₂) pulse chemisorption measurements. The influence of Cu on the Pd-Cu/γ-Al₂O₃ bimetallic catalyst in the catalytic hydrodechlorination (HDC) of 4-chlorophenol (4-CP) in an aqueous phase in a mixing glass tank reactor was studied using H₂ as the reducing agent. Compared with a Pd/γ-Al₂O₃ monometallic catalyst, adding Cu to modify the Pd catalyst changed the dispersion of Pd particles and surface area of the metals, thereby significantly influencing the catalytic performance in the HDC of 4-CP in an aqueous phase. The results demonstrated that adding Cu to the Pd catalyst improved the dispersion of Pd particles and increased the HDC catalytic activity when the Cu/Pd molar ratio was ≤0.5/1. In addition, the formation of a Pd-Cu alloy in the Pd-Cu bimetallic catalyst inhibited further hydrogenation of phenol, the hydrodechlorinated product of 4-CP. The Cu/γ-Al₂O₃ catalyst had an extremely low catalytic activity in the HDC of 4-CP; however, it did not catalyze the hydrogenation of phenol to form cyclohexanone. This journal is

Full text of DOI:10.1039/c4ra10798e

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Catalytic hydrodechlorination of 4-chlorophenol
over a series of Pd–Cu/g-Al2O3 bimetallic catalysts
Cite this: RSC Adv., 2014, 4, 59204
*
Deren Fang, Wanjun Li, Jinbo Zhao, Shang Liu, Xuanxuan Ma, Jinguang Xu
and Chuanhai Xia
Received 23rd September 2014
Accepted 3rd November 2014
DOI: 10.1039/c4ra10798e
www.rsc.org/advances
A series of Pd–Cu/g-Al2O3 bimetallic catalysts was prepared using the containing chlorinated organic compounds because HDC is
sequentially incipient wetness impregnation method. The catalysts advantageous compared with other potential techniques for
were characterized using X-ray diffraction, temperature programmed treating these hazardous pollutants. HDC proceeds at mild
reduction, scanning electron microscopy-energy dispersive X-ray, and conditions;3,4 it does not require high temperature and pressure
hydrogen (H2) pulse chemisorption measurements. The influence of as incineration or wet oxidation do.
Cu on the Pd–Cu/g-Al2O3 bimetallic catalyst in the catalytic hydro-
Research regarding the HDC of CPs has typically involved
dechlorination (HDC) of 4-chlorophenol (4-CP) in an aqueous phase in evaluating supported metal catalysts. Bulk or supported forms
a mixing glass tank reactor was studied using H2 as the reducing agent. of precious metals such as Pd,3–16 Pt,17 and Rh5,18 are widely used
Compared with a Pd/g-Al2O3 monometallic catalyst, adding Cu to as catalysts in HDC under liquid and gas phase conditions.
modify the Pd catalyst changed the dispersion of Pd particles and Among these metals, Pd is the most active and selective cata-
surface area of the metals, thereby significantly influencing the cata- lyst.19 However, the high cost of Pd hinders its practical appli-
lytic performance in the HDC of 4-CP in an aqueous phase. The results cation. In recent years, studies have explored the modication
demonstrated that adding Cu to the Pd catalyst improved the of supported Pd monometallic catalysts by combining Pd with a
dispersion of Pd particles and increased the HDC catalytic activity different transitional metal. Several Pd-based bimetallic sup-
when the Cu/Pd molar ratio was #0.5/1. In addition, the formation of a ported catalysts and nanoparticles, such as Pd–Ni,20 Pd–Fe,21
Pd–Cu alloy in the Pd–Cu bimetallic catalyst inhibited further hydro- Pd–Mg,22 and Pd–Al,23 have been widely explored for use in
genation of phenol, the hydrodechlorinated product of 4-CP. The Cu/ HDC. These catalysts provided more satisfactory catalytic
g-Al2O3 catalyst had an extremely low catalytic activity in the HDC of activity in HDC than monometallic catalysts did. In addition,
4-CP; however, it did not catalyze the hydrogenation of phenol to hydroisomerization of the product of the HDC of CCl4 was
form cyclohexanone.
observed when Cu was introduced to Pd/C.24
This study involved preparing Al2O3-supported Pd–Cu
bimetallic catalysts by using the incipient wetness impregna-
tion method and examining the catalytic performance of these
catalysts in the HDC of 4-chlorophenol (4-CP) in an aqueous
phase by using molecular hydrogen as the reducing agent at
room temperature and normal pressure. 4-CP was effectively
hydrogenated during HDC; moreover, interesting reaction
phenomena were observed for the rst time.
1. Introduction
Chlorophenols (CPs) are widely used in manufacturing pesti-
cides, disinfectants, wood preservatives, and personal care
formulations and are the byproducts of several industrial
processes.1 However, a growing concern regarding the toxicity
and environmental fate of these compounds has led to strict
government regulations. Five CPs are listed by the United States
Environmental Protection Agency as priority pollutants,1,2 and
efficient (catalytic) methods must be developed for eliminating
poorly biodegradable CPs released from industrial effluents and
polluted groundwater.
2. Experimental section
2.1 Catalyst preparation
Beads composed of g-Al2O3 with a diameter of 0.5–1 mm were
used as the support, and the Pd–Cu bimetallic catalysts were
prepared using the sequentially incipient wetness impregnation
method. The content of the noble metal (Pd) was xed at 1 wt%,
and the Cu content was varied to obtain the Cu/Pd molar ratios
0.1/1, 0.25/1, 0.5/1, 1/1, 3/1, and 5/1 for catalysts that were
In past years, catalytic hydrodechlorination (HDC) has
received increasing attention for the treatment of wastewater
Institute of Applied Catalysis, Yantai University, Yantai 264005, China. E-mail: fdr@
ytu.edu.cn
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Table 1 The dispersion and surface area of Pd of the catalysts
designated JZ-1, JZ-2, JZ-3, JZ-4, JZ-5, JZ-6, respectively. A typical
catalyst preparation method was used to impregnate the
precursors of the catalysts with the designated amount of
aqueous Cu(NO3)2 to yield the desired content (wt%) of Cu and
then dried at 110 ꢀC for 2 h and calcined at 350 ꢀC for 2 h. Aer
cooling, the catalysts were impregnated with aqueous PdCl2,
and then dried at 110 ꢀC for 2 h and calcined in air at 350 ꢀC for
2 h. The monometallic catalysts with Pd or Cu content of 1%
were prepared using the aforementioned procedure and were
designated 1% Pd and 1% Cu, respectively. The catalysts were
reduced before HDC was performed using aqueous NaBH4 at
room temperature and crashed to the size of 0.045–0.075 mm.
Molar ratios
of Cu/Pd
Pd dispersion
(%)
Pd surface area
Catalysts
(m2 gꢁ1
)
1% Pd
JZ-1
JZ-2
JZ-3
JZ-4
JZ-5
JZ-6
—
24.9
31.2
34.1
38.2
22.6
16.0
15.8
55.6
69.6
75.9
85.2
50.5
35.7
35.1
0.1/1
0.25/1
0.5/1
1/1
3/1
5/1
2.2 Catalyst characterization
X-ray diffraction (XRD) patterns were obtained using the Rigaku
D/MAX-2500 diffractometer with Cu Ka radiation (40 kV, 100
mA). Scanning electron microscopy (SEM) images were
obtained using a Hitachi S-4800 FE-SEM equipped with a
computer system for performing automatic operation and data
processing. The dried sample was carefully transferred to a
carbon tape on the SEM template, coated using a gold coater,
and analyzed using SEM at 10 kV. Energy dispersive X-ray (EDX)
experiments were performed using an EX-350 EDX micro-
analyzer equipped with a computer system for conducting
automatic operation and data processing. EDX mapping was
performed to visualize elemental and spatial information
regarding Cu and Pd on the Al2O3 surface. The particle
morphology and size distributions of Pd and Cu were deter-
mined by transmission electron microscopy (TEM/EDX), in a
JEOL JEM2000EXII microscope.
Temperature-programmed reduction (TPR) was performed
using a TP5000 multifunction absorber. The catalyst weight was
50 mg, the particle size was 60–80 mesh, a mixture of 10% H2/
90% N2 was used as the reduction gas, and the temperature was
Scheme 1 Schematic diagram of reaction device.
increased from 20 to 300 ꢀC at a rate of 5 ꢀC minꢁ1
.
Consumption of H2 was detected using a thermal conduction
detector (TCD).
200 mL aqueous mixture of 4-CP (1000 ppm) and NaOH (NaOH/
4-CP molar ratio ¼ 1.1/1). Next, H2 was introduced into the
reactor at a rate of 50 mL minꢁ1, thus initiating the HDC. Aer
15 min, 1 mL of the solution was extracted and analyzed by
using gas chromatography, a ame ionization detector, and a
polyethylene glycol capillary column.
H2 pulse chemisorption measurements of the catalysts were
performed using a TP5000 multifunction absorber and the
TCD. The catalyst weight was 0.10 g. Before the H2 pulse
chemisorption measurements were performed, the catalysts
were activated at 623 K for 2 h by using a ow of pure H2 at
atmospheric pressure. The catalysts were then degassed at 623
K for 2 h under owing Ar and cooled to 308 K. Next, H2 (5 vol%)
was injected into the Ar stream owing through the sample bed.
The injection loop was 0.5 mL. In the subsequent metal
dispersion calculations, H2 was assumed to be chemisorbed
only on the Pd ensembles. The surface area and dispersion of Pd
of the catalysts are listed in Table 1.
3. Results and discussion
Fig. 1 shows the XRD patterns of the catalysts. Diffraction peaks
of the g-Al2O3 support at 2q equals to 37.2ꢀ, 45.9ꢀ and 66.6ꢀ were
expected in the XRD patterns of Pd/g-Al2O3 and Pd–Cu/g-Al2O3
(JCPDS 10-0425), but Pd and Cu has not detected. Because of the
low content of Pd and Cu in the catalysts, the reection peak of
which were covered by the background of g-Al2O3, and was
2.3 Studies of catalytic HDC
HDC of 4-CP (Sigma, purity >99.6%) was performed at atmo- difficult to observe. The results of TEM demonstrated that the
spheric pressure in a mixing glass tank reactor (demonstrated particle size of the Pd and Cu of the catalysts were in the range
in Scheme 1) with electromagnetic stirring to ensure full contact of 2–3 nm (Fig. 2), so it is difficult to use the XRD determination
between the catalyst and the reactant. Aer reduction of phase of Pd and Cu of the catalysts. According to the EDX
(described in Section 2.1), 0.2 g of the catalyst was added to a analysis of JZ-3 (Cu/Pd ¼ 0.5/1), the peaks corresponding to Pd
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Fig. 1 XRD patterns of the reduced catalysts with different molar ratio
of Cu to Pd (a): 1% Pd, (b): JZ-1 (Cu/Pd ¼ 0.1/1), (c): JZ-2 (Cu/Pd ¼
0.25/1), (d): JZ-3 (Cu/Pd ¼ 0.5/1), (e): JZ-4 (Cu/Pd ¼ 1/1), (f): JZ-5 (Cu/
Pd ¼ 3/1), (g): JZ-6 (Cu/Pd ¼ 5/1), (h): g-Al2O3.
and Cu were observed (Fig. 3), indicating that Pd and Cu were
present on the surface of the catalysts.
The dispersion of Pd and surface areas of the bimetallic
catalysts were studied using H2 pulse chemisorption measure-
ments,25 and the results are illustrated in Table 1. Compared
with the 1% Pd monometallic catalyst, bimetallic catalysts with
Cu/Pd molar ratios of 0.1/1, 0.25/1, and 0.5/1 (JZ-1, JZ-2, and JZ-
3, respectively) exhibited incrementally greater dispersions of
Pd and surface areas. However, bimetallic catalysts with Cu/Pd
molar ratios of 1/1, 3/1, and 5/1 (JZ-4, JZ-5, and JZ-6, respectively)
exhibited incrementally lower dispersions of Pd and surface
areas, indicating that adding Cu changed the dispersion of Pd
and the surface areas of the bimetallic catalysts. Adding an
appropriate amount of Cu increased the dispersions of Pd and
surface areas of Pd-based bimetallic catalysts compared with
those of the Pd monometallic catalyst.
Fig. 4 shows H2-TPR proles of the catalysts. The TPR
proles of 1% Pd and 1% Cu monometallic catalysts showed
only one reduction peak, and their reduction temperatures were
358 K and 472 K, respectively. The negative peak of 1% Pd at 431
K corresponded to the decomposition of Pd b-hydride.26
The TPR proles of the Pd–Cu bimetallic catalysts were
different from those of the 1% Pd and 1% Cu monometallic
catalysts. The TPR prole of JZ-1 (Cu/Pd molar ratio ¼ 0.1/1) was
similar to that of the 1% Pd monometallic catalyst, indicating
that adding a small amount of Cu to the Pd monometallic
catalyst did not alter the microstructure of the Pd particle. As
the Cu content was increased (JZ-2, JZ-3, JZ-4, JZ-5, and JZ-6), the
TPR proles gradually became more complex. Three reduction
peaks appeared in the TPR proles of these catalysts; the
reduction peak centered at 358 K was attributed to PdO, the
reduction peak in the range 433–463 K was attributed to CuO,
and the reduction peak in the range 393–413 K (middle peak)
was attributed to the interaction between PdO and CuO, which
transformed into Pd–Cu alloy particles aer the reduction.27,28
Fig. 2 TEM micrographs of reduced Pd–Cu/g-Al2O3 catalysts (a) JZ-3
(Cu/Pd ¼ 0.5/1), (b) JZ-4 (Cu/Pd ¼ 1/1), (c) JZ-6 (Cu/Pd ¼ 5/1).
The TPR proles of JZ-2 (Cu/Pd ¼ 0.25/1), JZ-3 (Cu/Pd ¼ 0.5/1),
JZ-4 (Cu/Pd ¼ 1/1), JZ-5 (Cu/Pd ¼ 3/1), and JZ-6 (Cu/Pd ¼ 5/1)
clearly showed that the intensity of the middle peak (PdO–
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Fig. 4 The TPR profiles of the catalysts (a): 1% Pd, (b): JZ-1 (Cu/Pd ¼
0.1/1), (c): JZ-2 (Cu/Pd ¼ 0.25/1), (d): JZ-3 (Cu/Pd ¼ 0.5/1), (e): JZ-4
(Cu/Pd ¼ 1/1), (f): JZ-5 (Cu/Pd ¼ 3/1), (g): JZ-6 (Cu/Pd ¼ 5/1), (h): 1%
Cu.
of Pd and surface area of the catalysts. The dispersion of Pd and
surface area of the catalysts followed the order JZ-3 > JZ-2 > JZ-1
> 1% Pd > JZ-4 > JZ-5 > JZ-6, which is consistent with the order of
the catalytic activity of the catalysts. Among all catalysts, JZ-3
had the highest dispersion of Pd and surface area; therefore,
JZ-3 showed the highest catalytic activity in the HDC of 4-CP.
According to the gas chromatography-mass spectrometry
analysis, in addition to phenol, cyclohexanone was a product in
the HDC of 4-CP in an aqueous phase. This indicated that the
HDC of 4-CP was a tandem reaction in which 4-CP was rst
hydrogenated to form phenol over 1% Pd and Pd–Cu bimetallic
catalysts, and phenol was further hydrogenated to form cyclo-
hexanone.4,6,15,29 The change in the selectivity of the catalysts is
shown in Fig. 7a and b, and the reaction pathway is shown in
Scheme 2. Fig. 6 and 7 show that the competitive hydrogenation
Fig. 3 EDX image of reduced Pd–Cu/g-Al2O3 (Cu/Pd ¼ 0.5/1) catalyst.
CuO interaction species) as well as the reaction temperatures of phenol occurred in the HDC of 4-CP over 1% Pd and all Pd–
increased with the Cu content. Moreover, the intensity of the Cu bimetallic catalysts. For example, when 1% Pd was used in
reduction peak of PdO decreased. This indicates that, as the Cu the HDC of 4-CP, approximately 75% of 4-CP was hydrogenated
content in the Pd–Cu bimetallic catalysts was increased, the (Fig. 6) aer 30 min; furthermore, the selectivity of phenol and
amount of the Pd–Cu alloy increased. The TEM/EDX images cyclohexanone were approximately 98.36% (Fig. 7a) and 1.64%
(Fig. 5) demonstrated that in the same micro zone of JZ-3 and (Fig. 7b), respectively, indicating that the HDC of 4-CP and the
JZ-6 there coexist Pd and Cu, this means that the formation of hydrogenation of phenol occurred simultaneously over the 1%
Cu–Pd alloy on the catalysts.
Pd monometallic catalyst. For Pd–Cu bimetallic catalysts,
The catalytic HDC performance of the catalysts is shown in competitive hydrogenation between 4-CP and phenol occurred
Fig. 6. A marked difference in the catalytic activity of the cata- during the HDC of 4-CP (Fig. 7). Furthermore, the variation
lysts was observed. When the Cu/Pd molar ratios were 0.1/1, tendencies in the selectivity of phenol gradually decreased as
0.25/1, and 0.5/1, 4-CP was completely hydrodechlorinated the reaction time increased over 1% Pd and Pd–Cu bimetallic
within 60 min; however, when the Cu/Pd molar ratios were 1/1, catalysts (Fig. 7a). However, the selectivity of cyclohexanone
3/1, and 5/1, 4-CP was not completely hydrodechlorinated gradually increased for all 1% Pd and Pd–Cu bimetallic catalysts
within 60 min. The HDC catalytic activity of the catalysts fol- (Fig. 7b). According to these results, the catalytic activity of the
lowed the order JZ-3 > JZ-2 > JZ-1 > 1% Pd > JZ-4 > JZ-5 > JZ-6 > catalysts was concluded to follow the order JZ-1 > JZ-2 > JZ-3 >
1% Cu. This result indicated that a moderate amount of Cu 1% Pd > JZ-4 > JZ-5 > JZ-6 for the HDC of 4-CP; however the
added to modify the Pd monometallic catalyst improved the catalytic activity for the hydrogenation of phenol followed the
catalytic activity. According to the results shown in Table 1, the order 1% Pd > JZ-1 > JZ-2 > JZ-3 > JZ-4 > JZ-5 > JZ-6 in an aqueous
catalytic activity of the catalysts was correlated to the dispersion solution. Therefore, the Pd monometallic catalyst and the Pd–
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Fig. 5 TEM/EDX images of reduced catalyst JZ-3 and JZ-6 (a) JZ-3 (Cu/Pd ¼ 0.5/1), (b) Cu Ka1 in JZ-3, (c) Pd La1 in JZ-3, (d) JZ-6 (Cu/Pd ¼ 5/1),
(e) Cu Ka1 in JZ-6, and (f) Pd La1 in JZ-6.
Scheme 2 The equation of the HDC of 4-chlorophenol.
reaction process. The higher the Cu content in the Pd–Cu
bimetallic catalysts was, the lower the cyclohexanone selectivity
in the HDC of 4-CP. The TPR results (Fig. 4) showed that, as the
Cu content in the Pd–Cu bimetallic catalysts was increased, the
intensity of the reduction peak of PdO decreased, and the
reduction peak of the PdO–CuO interaction species increased;
in other words, as the Cu content was increased, the amount of
Pd particles in the Pd–Cu bimetallic catalysts gradually
decreased and the amount of the Pd–Cu alloy increased. This
means that the formation of the Pd–Cu alloy in the Pd–Cu
bimetallic catalysts did not favor the hydrogenation of phenol to
form cyclohexanone, which may require multiple adsorption or
plurality of an active center (demonstrated in Scheme 3). The Pd
monometallic catalyst not only catalyzed the hydrogenolysis of
Fig. 6 The influence of different catalysts on the conversion of 4-CP.
Cu bimetallic catalysts showed different catalytic activities in
the hydrogenolysis of the C–Cl bond of 4-CP and C]C double
bond of phenol. Compared with the 1% Pd monometallic
catalyst, adding Cu inhibited the formation of cyclohexanone in
the HDC of 4-CP over Pd–Cu bimetallic catalysts throughout the
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HDC of CP and did not catalyze the hydrogenolysis of phenol to
form cyclohexanone (Fig. 7b). The active center was mainly Pd
in both reactions. The formation of the Pd–Cu alloy reduced the
quantity of active Pd centers, thereby affecting the hydrogena-
tion of the benzene ring of phenol, and the hydrogenolysis of
the C–Cl bond of 4-CP required few active centers of Pd clusters.
The reason for the inhibition of the hydrogenation of the C]C
double bond of phenol by the Pd–Cu alloy in the Pd–Cu bime-
tallic catalysts is unclear and requires further investigation.
4. Conclusion
A series of Pd–Cu/g-Al2O3 bimetallic catalysts was prepared, and
their catalytic performance was studied in the HDC of 4-CP in
an aqueous phase. Compared with the Pd/g-Al2O3 mono-
metallic catalyst, adding a moderate amount of Cu to modify Pd
catalysts increased the dispersion of Pd and surface area of the
catalysts and considerably increased catalytic activity in the
HDC of 4-CP. However, adding an excessive amount of Cu to the
Pd–Cu/g-Al2O3 catalyst inhibited the HDC of 4-CP. In addition,
the Pd monometallic catalyst was more advantageous than the
Pd–Cu bimetallic catalysts because it catalyzed the hydrogena-
tion of phenol to form cyclohexanone, whereas the Pd–Cu alloy
in the Pd–Cu bimetallic catalysts was disadvantageous
because it inhibited the hydrogenation of phenol, the HDC
product of 4-CP.
Acknowledgements
This study was funded by the National Science Foundation of
China (no. 21377162). Thanks for the help of Prof. XM Wei of
Dalian Institute of Chemical Physics, Chinese Academy of
Sciences to do the experiment of TEM/EDX.
Fig. 7 The influence of the catalysts on the hydrogenation products.
References
1 S. Ramamoorthy and S. Ramamoorthy, Chlorinated Organic
Compounds in the Environment, CRC Press, Boca Raton, 1997.
2 USEPA, The Inventory of Sources of Dioxin in the United
States, EPA/600/P-98/00A2, 1998.
3 G. Yuan and M. A. Keane, Catal. Today, 2003, 88, 27.
4 C. Xia, Y. Liu, S. Zhou, C. Yang, S. Liu, J. Xu, J. Yu, J. Chen and
X. Liang, J. Hazard. Mater., 2009, 169, 1029.
5 E. Diaz, A. F. Mohedano, J. A. Casas, L. Calvo, M. A. Gilarranz
and J. J. Rodriguez, Appl. Catal., B, 2011, 106, 469.
6 Z. M. de Pedro, E. Diaz, A. F. Mohedano, J. A. Casas and
J. J. Rodriguez, Appl. Catal., B, 2011, 103, 128.
Scheme
adsorption.
3 Model of path-way of single point or multi-point
´
7 J. M. Moreno, M. A. Aramendıa, A. Marinas, J. M. Marinas
and F. J. Urbano, Appl. Catal., B, 2007, 76, 34.
´
´
8 S. Gomez-Quero, F. Cardenas-Lizana and M. A. Keane, Chem.
Eng. J., 2011, 166, 1044.
9 Z. J. Wu, C. X. Sun, Y. Chai and M. H. Zhang, RSC Adv., 2011,
1, 1179.
10 C. B. Molina, A. H. Pizarro, J. A. Casas and J. J. Rodriguez,
Appl. Catal., B, 2014, 148–149, 330.
11 L. Cheng, Z. Jin and X. Wang, Catal. Commun., 2013, 41, 60.
the C–Cl bond of 4-CP but also catalyzed the hydrogenation of
phenol. By contrast, the Pd–Cu bimetallic catalysts mainly
catalyzed the hydrogenolysis of the C–Cl bond of 4-CP, which
was possibly related to the formation of the Pd–Cu alloy. The
Cu/g-Al2O3 catalyst had an extremely low catalytic activity in the
This journal is © The Royal Society of Chemistry 2014
RSC Adv., 2014, 4, 59204–59210 | 59209

View Article Online
RSC Advances
Communication
12 Y. L. Ren, G. Y. Fan, W. D. Jiang, B. Xu and F. Liu, RSC Adv., 21 V. Nagpal, A. D. Bokare, R. C. Chikate, C. V. Rode and
2014, 4, 25440. K. M. Paknikar, J. Hazard. Mater., 2010, 175, 680.
13 X. X. Ma, Y. Liu, S. J. Liu and C. H. Xia, Appl. Catal., B, 2014, 22 S. Agarwal, S. R. Al-Abed and D. D. Dionysiou, Environ. Sci.
144, 580. Technol., 2007, 41, 3722.
14 C. H. Xia, Y. Liu, S. W. Zhou, C. Y. Yang, S. J. Liu, S. Z. Guo, 23 B. Yang, S. B. Deng, G. Yu, H. Zhang, J. H. Wu and Q. F. Zhuo,
Q. Liu, J. B. Yu and J. P. Chen, Catal. Commun., 2009, 10,
1443.
15 C. H. Xia, Y. Liu, J. Xu, J. B. Yu, W. Qin and X. M. Liang, Catal.
Commun., 2009, 10, 456.
J. Hazard. Mater., 2011, 189, 76.
24 M. Bonarowska, O. Machynskyy, D. Łomot, E. Kemnitz and
Z. Karpinski, Catal. Today, 2014, 235, 144.
ˇ
25 A. Pintar, J. Batista and I. Musevic, Appl. Catal., B, 2004, 52,
16 C. H. Xia, J. Xu, W. Z. Wu and X. M. Liang, Catal. Commun.,
2004, 5, 383.
49.
´
˜
´
26 O. S. G. P. Soares, J. J. M. Orfao, J. Ruiz-Martınez, J. Silvestre-
´
17 M. Bonarowska, Z. Kaszkur, L. Kepinski and Z. Karpinski,
Appl. Catal., B, 2010, 99, 248.
Albero, A. Sepulveda-Escribano and M. F. R. Pereira, Chem.
Eng. J, 2010, 165, 78.
´
18 C. S. Srikanth, V. P. Kumar, B. Viswanadham and 27 J. Sa and H. Vinek, Appl. Catal., B, 2005, 57, 247.
´
28 B. T. Meshesha, N. Barrabes, J. Llorca, A. Danov, F. Medina
K. V. R. Chary, Catal. Commun., 2011, 13, 69.
19 F. J. Urbano and J. M. Marinas, J. Mol. Catal. A: Chem., 2001,
173, 329.
¨
and K. Fottinger, Appl. Catal., A, 2013, 453, 130.
29 E. Diaz, J. A. Casas, A. F. Mohedano, L. Calvo, M. A. Gilarranz
20 N. Seshu Babu, N. Lingaia and P. S. Sai Prasad, Appl. Catal.,
B, 2012, 111–112, 309–316.
and J. J. Rodriguez, Ind. Eng. Chem. Res., 2008, 47, 3840.
59210 | RSC Adv., 2014, 4, 59204–59210
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