Catalytic hydrogenation of sulfur-containing nitrobenzene over Pd/C catalysts: In situ sulfidation of Pd/C for the preparation of PdxSy catalysts

Article abstract of DOI:10.1016/j.apcata.2015.02.043

The preparation of supported palladium sulfides catalysts has attracted much attention due to their good sulfur-resistant properties in the hydrogenation of sulfur-containing compounds. In this work, we unambiguously demonstrated that Pd/C catalyst could be in situ sulfided by organic sulfur-containing reactant molecules and the sulfidation was highly dependent on temperature. The in situ sulfidation of Pd/C catalyst was composed of a reaction of Pd with the sulfur derived from the cleavage of C-S bond of sulfur-containing reactant molecules, followed by a transformation to Pd_xS_y at high temperatures (around 120 °C). The sulfided Pd/C catalyst could be used for at least 18 recycles without a significant loss in its activity during the hydrogenation of sulfur-containing nitrobenzene at 180 °C with 3 MPa H₂, which could be attributed to the stable presence of Pd₄S and Pd₁₆S₇.

Full text of DOI:10.1016/j.apcata.2015.02.043

Applied Catalysis A: General 497 (2015) 17–21
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Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Catalytic hydrogenation of sulfur-containing nitrobenzene over Pd/C
catalysts: In situ sulfidation of Pd/C for the preparation of PdxSy
catalysts
Qunfeng Zhang, Wei Xu, Xiaonian Li∗, Dahao Jiang, Yizhi Xiang, Jianguo Wang,
Jie Cen, Stephen Romano, Jun Ni
Institute of Industrial Catalysis, Zhejiang University of Technology, State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology,
Hangzhou 310014, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The preparation of supported palladium sulfides catalysts has attracted much attention due to their
good sulfur-resistant properties in the hydrogenation of sulfur-containing compounds. In this work, we
unambiguously demonstrated that Pd/C catalyst could be in situ sulfided by organic sulfur-containing
reactant molecules and the sulfidation was highly dependent on temperature. The in situ sulfidation of
Pd/C catalyst was composed of a reaction of Pd with the sulfur derived from the cleavage of C S bond
of sulfur-containing reactant molecules, followed by a transformation to PdxSy at high temperatures
(around 120 ◦C). The sulfided Pd/C catalyst could be used for at least 18 recycles without a significant
loss in its activity during the hydrogenation of sulfur-containing nitrobenzene at 180 ◦C with 3 MPa H2,
which could be attributed to the stable presence of Pd4S and Pd16S7.
Received 30 September 2014
Received in revised form 19 February 2015
Accepted 26 February 2015
Available online 7 March 2015
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
On the other hand, sulfur-containing compounds may act
Sulfur-containing anilines are important intermediates for the
synthesis of medicines including antibiotic, insecticides, fungicides
and herbicides [1]. They are generally produced from the reduction
of sulfur-containing nitrobenzene using compounds such as NaS2,
N2H4, Fe/HCl and Zn/NH4Cl as nucleophilic reductants [2–5]. How-
ever, these reductants are hazardous to environment and make
the purification of final products difficultly. Green synthesis based
on heterogeneous catalytic hydrogenation of sulfur-containing
nitrobenzene is considered to be an attractive route for the prepa-
ration of thio-anilines (as shown in reaction 1) [6]. However, the
possible inhabitation of H2 dissociation by the strong chemisorp-
tion of sulfur-containing reactants on active sites of the metal
catalysts yet remains as a great challenge, which could result in
a sharp decline in the catalysts’ activities [7].
as catalyst promoter or selectivity modifier in heterogeneous
catalysis [8–10]. Moreover, pre-sulfided metal catalysts are well
known to be sulfur-resistant and have been extensively employed
for hydrodesulfurization (HDS) reactions at 240–360 ◦C [11,12].
The steady good catalytic properties of pre-sulfided metals are
attributed to the stable composition of active phases maintained
by the dynamic quasi-equilibrium between the chemical states of
the metal sulfides, in which the catalysts were reduced by H2 into
metallics, but immediately re-sulfided again by the sulfur from the
HDS of sulfur-containing compounds [13,14]. However, few knowl-
edge could be obtained about the thorough investigation of the
hydrogenation of organic sulfur-containing compounds (especially
of sulfur-containing nitrobenzene) over metal sulfides catalysts
[15–17]. It is probable that the dynamic equilibrium is hardly
available at low temperatures at which the liquid hydrogenation
is generally operated, which can finally lead to the deactiva-
tion of the catalysts during recycling process [15,16]. When the
hydrogenation reaction is carried out at higher temperature that
is close to the normal HDS reaction temperature, the selectiv-
ity of product is poor owing to the C S bond cleavage or the
rapid deactivation of the catalysts due to the coke formation
[18,19].
Catalyst
R − S − Ph − NO2 + 3H2 −→ R − S − Ph − NH2
+ 3H O R = C H
, Ph, Ph − S
2n+1
(1)
(
)
n
2
∗
Corresponding author. Tel.: +86 571 88320002.
E-mail address: xnli@zjut.edu.cn (X. Li).
http://dx.doi.org/10.1016/j.apcata.2015.02.043
0926-860X/© 2015 Elsevier B.V. All rights reserved.

18
Q. Zhang et al. / Applied Catalysis A: General 497 (2015) 17–21
Supported Pd sulfides are generally recognized as more appro-
priate catalysts for the hydrogenation of organosulfur because of
their higher hydrogenation and lower hydrogenolysis activity of
C
S bond than other metal sulfides catalysts [20–23]. However,
very limited information is available on the catalytic stability and
the active phase of palladium sulfides catalysts for the hydro-
genation of organosulfur. Novakova et al. found that high H2
pressure could inhibit the chemisorption of sulfur on 10-wt%
Pd/C catalyst during the hydrogenation/hydrogenolysis of 4,4ꢀ-
dinitrodiphenyldisulfide to 4-aminothiophenol and the catalyst
could be reused for 7 times [15]. Nevertheless, there was still a
clear decrease in the reaction rate with the increase of the recy-
cle numbers. They suggested that the decreased activity might be
due to the transformation of an active amorphous surface sulfide
into an inactive phase (e.g. Pd4S) [15]. But Miller et al. reported that
the dissociation rate of H2 on the Pd4S surfaces could still reach
one third of that of metal Pd at 450 ◦C even in the presence of H2S
[24,25]. Moreover, supported palladium sulfides catalysts are gen-
erally synthesized through pre-sulfidation of supported Pd metal
catalysts using H2S, Na2S or organic sulfur-containing molecules as
vulcanizators, but such method has the problem of high environ-
mental pollution and high industrialization cost [20–28].
Fig. 1. Hydrogenation of 4-nitrothioanisole on Pd/C catalyst at various tempera-
tures. Reaction conditions: 0.2 g 10 wt.% Pd/C, 20 g substrate, 150 mL toluene, 3 MPa
of H2, and reaction time of 660 min for the temperatures of 60–180 ◦C, 570 and
440 min for 190 and 200 ◦C, respectively.
Therefore, the aim of our study is to develop a novel “green”
method to produce supported palladium sulfides catalyst, and
obtain more detailed insight into their stability and active phases.
We discovered a key phenomenon known as in situ sulfidation that
Pd supported on activated carbon could be sulfided by the sulfur
from sulfur-containing compounds to form PdxSy (e.g. Pd3S, Pd16S7
and PdS) during the hydrogenation of sulfur-containing nitroben-
zene. The stability of the in situ sulfided catalyst and the activity of
the various active phases of palladium sulfides were investigated
through XRD and XPS characterization. Temperature was found to
be a dominant factor in the in situ sulfidation process. The in situ
sulfidation can reduce the cost of catalyst preparation by avoiding
the pre-sulfidation of metal catalysts using H2S as vulcanizator, but
also render the catalyst a better activity and stability in the hydro-
genation of sulfur-containing nitrobenzene, which will be of great
significance to future commercial applications.
using the value of contaminant carbon (C 1s = 284.8 eV) as a refer-
ence.
2.2. Hydrogenation tests
0.2 g of Pd/C catalyst, 20 g of 4-nitrothioanisole (AR/99.7%, Hubei
Laohekou Chemical Co. Ltd.) and 150 mL of toluene were charged
into a 500 mL stainless steel autoclave. The reactor was pressur-
ized with H2 to 3 MPa after being heated up to the desired reaction
temperatures (60–200 ◦C).
For recycling reactions, 1.0 g of Pd/C catalyst was used for
the hydrogenation of 4-nitrothioanisole with a catalyst/substrate
weight ratio of 1:20 at 180 ◦C and 3 MPa. The used catalyst
was then filtered, washed with toluene (3 × 10 cm3) at room
temperature. 0.1 0.01 g of catalyst after each reaction was
characterized by XRD, and the residual catalyst was reused in reac-
tions.
In order to study the universality of in situ sulfidation in the
hydrogenation of sulfur-containing compounds, the hydrogena-
tion reactions of a series of these compounds as listed in Table 1
(AR/98%, Aladdin reagent Co. Ltd.) were performed in a 75 mL stain-
less steel autoclave reactor under the conditions of 2.0 g substrates,
0.05 g Pd/C, 10 mL toluene, and at 180 ◦C and H2 pressure of 3.0 MPa.
All reaction products were analyzed by gas chromatography (Shi-
madzu GC-2014) equipped with FID and a capillary column HP-5
(ϕ0.320 mm × 30 m).
2. Experiments and methods
2.1. Catalysts preparation and characterization
The sample of 10 wt%-Pd/C catalyst was prepared by the impreg-
nation method [29], and its specific surface area (SBET) was
measured to be 1563 m2 g−1. Prior to the impregnation, a commer-
cial activated carbon (China National Medicines Corporation Ltd.)
was pretreated with 2.5% HNO3 at 80 ◦C for 6 h. The pretreated
carbon was then washed with distilled water until the pH was 7
and outgassed in vacuum at 120 ◦C overnight. The pretreatment
is beneficial to create an appropriate density of total acidity on
the activated carbon for the preparation of Pd/C catalysts [29]. A
volume of 3 mL H2PdCl4 (Hangzhou Kaida Metal Catalyst & Com-
pounds Co. Ltd.) aqueous solution (0.05 g mL−1) was dropped into
the suspension of 1.5 g of activated carbon, and the pH value of the
solution was regulated to 11 by the addition of NaOH aqueous solu-
tion. Eventually, the catalyst was reduced with hydrazine hydrate
at room temperature, and dried at 110 ◦C for 7 h.
Characterization of the catalysts were carried out by powder
XRD at room temperature before and after the hydrogenation reac-
tion using an X’Pert PRO diffractometer (PNAlytical Co.) equipped
with a Cu K␣ radiation source operating at 40 kV and 40 mA.
XPS measurements were performed on a Thermo ESCALAB 250
Axis Ultra spectrometer using monochromatic Al K␣ radiation
(hꢀ = 1486.6 eV). All binding energy (BE) values were calibrated by
Here, the yield of the desired product was defined as the con-
version of the reactant multiplied by the selectivity of the desired
product.
3. Results and discussion
3.1. In situ sulfidation of Pd/C with sulfur-containing reactants
Fresh Pd/C catalyst was used for the hydrogenation of 4-
nitrothioanisole at 60–200 ◦C and 3 MPa of H2 pressure, and the
experimental results are shown in Fig. 1. The yield of desired
product (4-aminothioanisole) and the reaction rate at 60 ◦C were
only 7.4% and 0.11 gsub min−1
g
,
respectively. However,
−1
Pd
these values increased with increasing the reaction temperature.
When the reaction temperature was raised to 180 ◦C, the yield of
4-aminothioanisole increased to 99.5% and the reaction rate to
1.5 gsub min−1 gP−d1. It was also noted that when the temperature

Q. Zhang et al. / Applied Catalysis A: General 497 (2015) 17–21
19
Table 1
Results on the hydrogenation of sulfur-containing compounds over Pd/C catalyst.
Entry Reactant
Product
1st run
2nd run
Reaction
time (min)
Conversion
(%)
Selectivity
(%)
Reaction
time (min)
Conversion
(%)
Selectivity
(%)
1
40
100
99.7
310
100
99.8
2
3
4
5
30
45
100
100
100
98.1
99.8
99.7
10
220
340
100
100
100
98.6
99.6
99.8
5
6
60
70
100
100
97.5
96.7
390
440
100
100
98.3
96
Reaction condition: 0.05 g Pd/C, 2.0 g substrate, 10 mL toluene, 3 MPa, 180 ◦C.
was increased above 120 ◦C, aniline became the sole byproduct
most likely due to the cleavage of C S bond of 4-aminothioanisole.
We then performed the hydrogenation of 4-nitrothioanisole
over the used catalysts at the corresponding initial hydrogenation
temperatures of 60, 180 and 200 ◦C, respectively. No hydrogena-
tion of 4-nitrothioanisole was detected over the used catalysts at
60 ◦C. This is probably because the active metal sites of Pd/C were
blocked by sulfur-containing molecules, inhibiting the dissociation
of H2 and the consequent migration of hydrogen atoms on the Pd
surface [30]. In contrast, 4-nitrothioanisole could be completely
converted into 4-aminothioanisole at 180 and 200 ◦C after reacting
for 1100 and 850 min, respectively, but−t1he hydrogenation rates
decreased to 0.9 and 1.2 gsub min−1 gPd at these two respective
temperatures.
3.2. Mechanism of in situ sulfidation Pd/C
According to the XPS results (Fig. 3) of the catalyst used at
60–200 ◦C, the S2p peaks at 163.1–163.6 and 168.6–169.3 eV were
ascribed to NO2PhSMe and sulfate (S6+), respectively [31]. And a
special S2p peak at 164.6–164.9 eV emerged when the tempera-
ture increased to 120 ◦C, which was most likely attributed to Sn
[32]. However, this S2p peak was not detected in the XPS spec-
tra of the catalyst used at 60 ◦C. Combining the XRD and XPS
results, we highly believe the sulfidation process was a step-wise
process which might comprise (1) C S bond cleavage, (2) in situ
sulfidation from point to surface and (3) finally to bulk of Pd crys-
tal particles. Specifically, it started with the strong anchoring of
After the reactions, the catalysts were characterized by XRD
(Fig. 2) in order to investigate the effect of the temperature on their
catalytic performance in the hydrogenation reactions. The XRD pat-
terns showed that there was no change for the catalyst used at 60 ◦C
since only diffraction peaks of metal Pd could be observed. Interest-
ingly, at the reaction temperature above 120 ◦C, two new diffraction
peaks at around 39.4◦ and 35.1◦ were observed, which are associ-
ated with Pd4S. The formation of Pd4S phase seemed to be more
profound with higher reaction temperature and a complete trans-
formation of Pd into Pd4S phase was observed at 200 ◦C. Combining
with the product analysis in Fig. 1, we discovered the phenomenon
known as in situ sulfidation that Pd metal was sulfided by the sulfur
from the substrates. The repeated experiments with the used cata-
lysts at 180 and 200 ◦C revealed that the in situ sulfided “Pd4S” phase
was active for the hydrogenation of 4-nitrothioanisole, since 100%
conversion was obtained with prolonged reaction times. Novakova
et al. reported the use of the substrate-to-Pd molar ratio of 26:1
in their experiments to yield 98% after reacting for 360 min at
75 ◦C and claimed this molar ratio has almost reached the limit of
completely poisoning the catalyst surface [15]. While in our exper-
iments, the substrate-to-Pd mole ratio was 626:1, but the yield to
final products still kept above 98.2% even after reacting for 440 min
at 200 ◦C. The main factor causing the quite different results was
temperature.
Fig. 2. The XRD patterns of spent catalysts after the hydrogenation of 4-
nitrothioanisole at various temperatures. The XRD patterns of Pd and Pd4S phases
were assigned based on JCPDS PDF no. 0011201 and JCPDS PDF no. 731387, respec-
tively.

20
Q. Zhang et al. / Applied Catalysis A: General 497 (2015) 17–21
Fig. 3. XPS spectra of S 2p of the catalysts used at 60, 120, 160 and 200 ◦C.
sulfur-containing molecules onto the Pd surface, which modified
the structure of the metal valence band by decreasing the density of
states near the Fermi level at low reaction temperature [33]. Then,
the cleavage of the C S bond transpired to form NO2PhSH, MeSH
and H2S at higher temperatures after the adsorption of sulfur-
containing molecules on the surface of Pd [34,35]. Subsequently,
the reaction of H2S with surface Pd atoms took place, forming the
initial sulfides with a bilayer structure (sulfide/metal) [36]. Finally,
the diffusion of Pd vacancies ensued after surface sulfidation and
Pd4S was then formed [27]. Hence, it can be concluded that at 60 ◦C,
organic sulfur compounds adsorbed on the surface of metal Pd and
caused the deactivation of the catalyst. When the reaction temper-
ature increased above 120 ◦C, the decomposition of the adsorbed
organic sulfur compounds on the surface of metal Pd and the sufi-
dation of Pd metal and Sn to form new active phase “Pd4S” could
be carried out [36]. As demonstrated in the repeated experiments,
the catalysts after the in situ sulfidation process exhibited a lower
activity than those used in the first run, indicating that Pd4S has
a lower activity than that of metal Pd. Meanwhile, the amount of
byproduct (aniline) decreased during the recycling reactions. This
is probably due to the lower activation barriers for H2 dissociation
and C S bond cleavage on the surface of Pd4S than that of Pd metal
[27].
transformation of palladium sulfides catalysts during the recycling
reactions and further correlate the catalytic performance with the
species of palladium sulfides. The experimental results in Fig. 4
show the catalytic performance of Pd/C in each of 18 recycles with
a catalyst-to-reactant weight ratio of 1:20 at 180 ◦C and H2 pres-
sure of 3 MPa. It can be seen that the yield was maintained above
98% for each reaction. In addition, it was found that the average
reaction rate decreased from 10 to 0.37 gsub min−1 gP−d1 in the first
three recycles. The decrease of the hydrogenation rate during the
recycling was similar to the result as described above. However,
the catalyst activity was maintained in the reaction rate range of
0.37 − 0.54 gsub min−1
g
from the 3rd to the 18th recycling,
−1
Pd
which was much better than the results reported by Novakova et al.
[15].
The XRD analysis of the recycled catalyst (Fig. 5) reveals in
details how Pd sulfides reconstructed during the hydrogenation
process. A complete sulfidation of metal Pd into Pd4S was achieved
after two recycling reactions as the peaks for Pd totally disappeared,
and the formed Pd4S could be observed throughout the 18 recycles.
The hydrogenation of a series of sulfur-containing compounds
other than 4-nitrothioanisole was also investigated at 180 ◦C and
3 MPa of H2. As shown in Table 1, using Pd/C catalysts, and all
tested reactants were converted into the corresponding products
with superior yields in either first or recycling reactions. The main
by-product was aniline due to the hydrodesulfurization. In addi-
tion, the hydrogenation/hydrogenolysis of dinitrodiphenyl was
achieved, indicating that in situ sulfided Pd/C catalyst was also
capable of cleaving S S bond.
3.3. Reconstruction of Pd sulfides during recycling
It is well known that the stability of catalysts is of great impor-
tance from industrial point of view. Previous studies showed that
other palladium sulfides crystalline phases including Pd3S, Pd16S7
and PdS could also be formed after the complete transformation
of Pd into Pd4S. Therefore, it is necessary to investigate the phase
Fig. 4. The reaction rate and products yield of Pd/C catalyst against recycling num-
ber. Reaction conditions: 1 g Pd/C, 20 g 4-nitrothioanisole, 150 mL toluene, 180 ◦C,
3 MPa H2.

Q. Zhang et al. / Applied Catalysis A: General 497 (2015) 17–21
21
two phases were mainly responsible for the adsorption and the
activation of H2 and sulfur-containing compounds. The catalytic
stability of the in situ sulfided catalyst could be attributed to the
stable presence of Pd4S and Pd16S7.
Acknowledgments
This work was financially supported by National Natural Science
Foundation of China (NSFC-21406199) and National Basic Research
Program of China (973 Program) (no. 2011CB710800).
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/j.apcata.
2015.02.043.
References
Fig. 5. The XRD patterns of the Pd/C catalyst recycled in reactions. The XRD patterns
of Pd16S7, Pd3S and PdS phases were assigned based on JCPDS PDF no. 752228, JCPDS
PDF no. 731831 and JCPDSPDF no. 741060, respectively.
[1] T.R. Jones, S.E. Webber, M.D. Varney, M.R. Reddy, K.K. Lewis, V. Kathardekar,
H. Mazdiyasni, J. Deal, D. Nguyen, K.M. Welsh, S. Webber, A. Johnston, D.A.
Matthews, W.W. Smith, C.A. Janson, R.J. Bacquet, E.F. Howland, C.L.J. Booth,
S.M. Herrmann, R.W. Ward, J. White, C.A. Bartlett, C.A. Morse, J. Med. Chem. 40
(1997) 677–683.
[2] F.G. Dowalo, M. Shade, B.L. Broomall, US Patent 3661944 (1972).
[3] L. Kael, P. Dieter, G. Harald, US Patent 4348335 (1982).
[4] J. Alex, G. Livry, G. Alain, B. Aulnaysous, L. Gerard, G. Saint, US Patent 5084067
(1992).
[5] G. Alain, B. Aulnaysous, US Patent 5542952 (1996).
[6] K. Iyad, Hydrogenation, InTech, Croatia, 2012, pp. 217–248.
[7] P. Tetenyi, in: J.S.J. Hargreaves, S.D. Jackson, G. Webb (Eds.), Isotopes
in Heterogeneous Catalysis, Imperial College Press, London, 2006, pp.
63–96.
[8] A.J. McCue, J.A. Anderson, Catal. Sci. Technol. 4 (2014) 272–294.
[9] Q.F. Zhang, J.C. Wu, C. Su, F. Feng, Q.L. Ding, Z.L. Yuan, H. Wang, L. Ma, C.S. Lu,
X.N. Li, Chin. Chem. Lett. 23 (2012) 1111–1114.
[10] Q.F. Zhang, C. Su, J. Cen, F. Feng, L. Ma, C.S. Lu, X.N. Li, Chin. J. Chem. Eng. 22
(2014) 1111–1116.
[11] C.S. Song, Catal. Today 86 (2003) 211–263.
[12] B. Sylvette, M. Damien, P. Guy, B. Christophe, D. Fabrice, Appl. Catal. A: Gen.
278 (2005) 143–172.
[13] E.W. Qian, K. Otani, L. Li, A. Ishihara, T. Kabe, J. Catal. 221 (2004) 294–301.
[14] J. Mijoin, G. Perot, F. Bataille, J.L. Lemberton, M. Breysse, S. Kasztelan, Catal. Lett.
71 (2001) 139–145.
[15] E.K. Novakova, L. Mclaughlin, R. Burch, P. Crawford, K. Griffin, C. Hardacre, P.J.
Hu, D.W. Rooney, J. Catal. 249 (2007) 93–101.
After the 3rd recycling, three new peaks at 36.0◦, 38.1◦ and 44.1◦
were detected possibly due to the formation of Pd3S, but they were
gradually faded out as the recycling number increased. Meanwhile,
additional peaks at 35.5◦, 37.7◦, 43.1◦ and 50.1◦ were observed with
the increase of recycling numbers, which might associate with the
transformation of Pd3S or Pd4S to Pd16S7 phase [36]. The presence
of peaks at 31.1◦ and 34.0◦ indicated that only a trace amount of
PdS was found after the 5th recycling. Recently, we have prepared a
series of Pd4S/C, Pd3S/C, Pd16S7/C and PdS/C catalysts in our previ-
ous study [27], and found that their catalytic activities in the hydro-
genation of 4-nitrothioanisole were ranked in the following order:
Pd16S7/C ≥ Pd4S/C > Pd3S/C ꢁ PdS/C (Fig. S1). Noted that the
sulfur in PdS phase is almost not mobile, which can cause its activity
be much lower than that of other palladium sulfides catalysts [13].
If the metal Pd was entirely in situ sulfided into Pd3S or PdS, the
catalyst would be deactivated completely. On the other side, if the
amounts of Pd3S and PdS were just a few, the activity of the catalyst
would be remained due to the activity of Pd16S7 was only a little
higher than that of Pd4S. In our experiments, a little bit of Pd3S was
detected in the 3rd recycling and then it faded out as the recycling
number increased, and a trace amount of PdS was found after the
5th recycling. Although the amounts of PdS4 and Pd16S7 phases
were changed during the 3rd to the 18th recycling, the amounts of
Pd3S and PdS were not increased significantly. Therefore, as long
as metal Pd was not entirely in situ sulfided into PdS, the catalyst
could render a better activity and stability in the hydrogenation of
sulfur-containing nitrobenzene. This should be the reason for the
reaction rate was remained during the 3rd to the 18th recycling.
[16] L. McLaughlin, E. Novakova, R. Burch, C. Hardacre, Appl. Catal. A: Gen. 340
(2008) 162–168.
[17] F.S. Dovell, H. Greenfield, US Patent 3336386 (1967).
[18] L.V. Manuilova, V.P. Fedin, Y.V. Mironov, E.M. Moroz, T.V. Pasynkova,
V.I. Zaikovskii, T.S. Sukhareva, React. Kinet. Catal. Lett. 54 (1995)
281–286.
[19] T.P. Voskresenskaya, T.S. Sukhareva, React. Kinet. Catal. Lett. 36 (1988)
307–311.
[20] T. Kabe, W. Qian, Y. Hirai, L. Li, A. Ishihara, J. Catal. 190 (2000) 191–198.
[21] A.V. Mashkina, L.G. Sakhaltueva, Kinet. Catal. 43 (2002) 107–114.
[22] A.V. Mashkina, A.A. Zirka, Kinet. Catal. 41 (2000) 521–526.
[23] A.A. Zirka, A.V. Mashkina, Kinet. Catal. 41 (2000) 388–393.
[24] J.B. Miller, D.R. Alfonso, B.H. Howard, C.P. O’Brien, B.D. Morreale, J. Phys. Chem.
C 113 (2009) 18800–18806.
[25] C.P. O’Brien, B.H. Howard, J.B. Miller, B.D. Morreale, A.J. Gellman, J. Membr. Sci.
349 (2010) 380–384.
[26] F. Menegazzo, P. Canton, F. Pinna, N. Pernicone, Catal. Commun. 9 (2008)
2353–2356.
[27] W. Xu, J. Ni, Q.F. Zhang, F. Feng, Y.Z. Xiang, X.N. Li, J. Mater. Chem. A 1 (2013)
12811–12817.
4. Conclusion
In this study, in situ sulfidation of Pd/C by sulfur-containing
compounds for the preparation of PdxSy/C catalyst was proposed.
The in situ sulfided catalyst showed excellent performance in the
hydrogenation of sulfur-containing nitrobenzene and there was no
significant loss in the activity and yield during the recycling reac-
tions. Both the cleavage of C S bond of sulfur-containing reactants
and the followed reaction of Pd metal with sulfur could only be ini-
tiated at higher temperatures (around 120 ◦C), indicating that the
in situ sulfidation of Pd/C catalyst was highly dependent on temper-
ature. The hydrogenation rate of sulfur-containing nitrobenzene
was much higher over Pd4S and Pd16S7 phases, indicating that the
[28] A. Mori, T. Mizusaki, M. Kawase, T. Maegawa, Y. Monguchi, S. Takao, Y. Takagi,
H. Sajiki, Adv. Synth. Catal. 350 (2008) 406–410.
[29] J.Y. Li, L. Ma, X.N. Li, C.S. Lu, H.Z. Liu, Ind. Eng. Chem. Res. 44 (2005) 5478–5482.
[30] F.J. Castro, G. Meyer, G. Zampieri, J. Alloys Compd. 330 (2002) 612–616.
[31] J.-M. Manoli, C. Potvin, M. Muhler, U. Wild, G. Resofszki, T. Buchholz, Z. Paal, J.
Catal. 178 (1998) 338–351.
[32] C. Gillan, M. Fowles, S. French, S.D. Jackson, Ind. Eng. Chem. Res. 52 (2013)
13350–13356.
[33] F.-M. McKenna, J.A. Anderson, J. Catal. 281 (2011) 231–240.
[34] J.C. Love, D.B. Wolfe, R. Haasch, M.L. Chabinyc, K.E. Paul, G.M. Whitesides, R.G.
Nuzzo, J. Am. Chem. Soc. 125 (2003) 2597–2609.
[35] C.H. Paterson, R.M. Lambert, Surf. Sci. 187 (1987) 339–358.
[36] D.-C. Pablo, I.J. Ferrer, J.R. Ares, C. Sanchez, J. Phys. Chem. C 113 (2009)
5329–5335.