Selective hydrogenation of phenol to cyclohexanone in water over PD@N-doped carbon derived from ionic-liquid precursors

Article abstract of DOI:10.1002/cctc.201402561

In this report, a kind of mesoporous N-doped carbon (CN-x) derived from N-containing ionic-liquid (IL) precursors were synthesized, and Pd@CN-x prepared by a simple ultrasound-assisted method showed higher catalytic activity for the selective hydrogenation of phenol and its derivatives under mild reaction conditions in water than commercial Pd@C and other common Pd heterogeneous catalysts. The catalytic activities of Pd@CN-x derived from different ILs were different, and further study into the influencing factors, including physical properties, N species of CN-x, and Pd status of Pd@CN-x, were performed. Being picky: N-Doped carbon (CN-x) derived from N-containing ionic-liquid precursors are used as Pd nanoparticle supports for the selective hydrogenation of phenol to cyclohexanone with high activity and selectivity under mild reaction conditions. The activities of the Pd@CN-x catalysts derived from a variety of ionic liquids are different, and studies on the physical properties, Pd status, and N species of the catalysts are performed.

Full text of DOI:10.1002/cctc.201402561

CHEMCATCHEM
COMMUNICATIONS
DOI: 10.1002/cctc.201402561
Selective Hydrogenation of Phenol to Cyclohexanone in
Water over Pd@N-Doped Carbon Derived from Ionic-Liquid
Precursors
Xuan Xu, Haoran Li, and Yong Wang*[a]
In this report, a kind of mesoporous N-doped carbon (CN-x)
derived from N-containing ionic-liquid (IL) precursors were syn-
thesized, and Pd@CN-x prepared by a simple ultrasound-assist-
ed method showed higher catalytic activity for the selective
hydrogenation of phenol and its derivatives under mild reac-
tion conditions in water than commercial Pd@C and other
common Pd heterogeneous catalysts. The catalytic activities of
Pd@CN-x derived from different ILs were different, and further
study into the influencing factors, including physical proper-
ties, N species of CN-x, and Pd status of Pd@CN-x, were per-
formed.
catalysts to achieve both excellent conversion and selectivity;
however, the catalyst could not be applied in a solvent such as
water.[10] Chen and co-workers reported an ionic-liquid-like co-
polymer stabilized palladium catalyst that showed 99% selec-
tivity and 99% conversion.[11] Polyaniline-functionalized carbon-
nanotube-supported palladium has also been used as an effi-
cient catalyst for the hydrogenation of phenol.[12] Shin et al.
used a multifunctional Pd/Sc(OTf)3/ionic liquid catalyst for the
direct conversion of phenol into caprolactam.[13] Our group dis-
covered that Pd on mesoporous graphitic carbon nitride
(Pd@mpg-C3N4) was an excellent catalyst for the hydrogena-
tion of phenols to the corresponding ketones.[14] However,
these catalytic systems only showed moderate activity. Alterna-
tive heterogeneous catalysts for the selective hydrogenation of
phenol with both high activity and high selectivity under am-
bient conditions are desirable.
The selective hydrogenation of phenol to cyclohexanone is
a popular issue in science and industry because of the impor-
tance of cyclohexanone in the production of nylon 6 and
nylon 66.[1] There are many advantages of the selective hydro-
genation of phenol over the oxidation of cyclohexane or the
two-step hydrogenation of phenol because selective hydroge-
nation of phenol to cyclohexanone avoids harsh reactions, un-
desirable byproducts, and so on.[2] Given that the degree of hy-
drogenation highly depends on the type of catalyst and the
support,[3] much of the work over the last decades has focused
on the development of highly effective and highly selective
catalysts for this process.[4]
The lack of reproducibility of the surface chemistry of pure
porous carbon materials puts a serious limitation on their
widespread use in applications, for example, in catalysis.
Indeed, carbon materials are generally oxidized by using H2O2
or HNO3 before they are used as host materials to introduce
more defects and strengthen the interactions between the
metal nanoparticles and the supports. Although surface activa-
tion of carbon materials is now a well-established process, it
requires rather harsh conditions because of the low reactivity
of the carbon materials. Nitrogen functionalization has been
used as a well-established method to stabilize metal nanoparti-
cles against oxidation. For example, Li et al. used nitrogen-
functionalized ordered mesoporous carbon as a Pd support for
the hydrogenation of phenol, and the activity and selectivity
were enhanced significantly.[15]
The selective hydrogenation of phenol is generally per-
formed in the vapor[5] or aqueous phase[6] with supported
metal catalysts, such as Pd, Pt, Ni, and Rh.[7] Pd is preferred in
most cases because of its high selectivity and relatively low
price. Metal oxides, zeolites, and carbon are common catalyst
supports. Activated carbon, carbon nanofibers, and hydrophilic
carbon have been used as supports for Pd owing to their high
surface area and uniform distribution of palladium particles on
them,[8] but the activity and/or selectivity has remained poor.
Zhao and co-workers reported that the combination of micro-
wave irradiation and Pd@C was efficient for the hydrogenation
of phenol to cyclohexanone in the presence of HCOONa as the
hydrogen source.[9] Han and co-workers used Pd@C–Lewis acid
Compared with nitrogen functionalization, in situ doping of
N atoms by using N-containing precursors can result in the ho-
mogeneous incorporation of nitrogen into carbon materials
with controlled chemistry, avoiding the potential loss of nitro-
gen functionality under reaction conditions, and is suitable for
stabilizing Pd nanoparticles against oxidation.[16] Herein, eight
examples of N-containing ionic liquids (ILs) including four pyri-
dinium ILs and four imidazolium ILs, as listed in Scheme 1,
were prepared and used as precursors to synthesize mesopo-
rous N-doped carbon materials by calcination under N2 flow,
which was developed recently.[16,17] The so-prepared eight N-
doped carbon materials are denoted as CN-x, (x=1–8), and
they were loaded with Pd nanoparticles by the ultrasound-as-
sisted method described by Wang et al.[16,18]
[a] X. Xu, Prof. Dr. H. Li, Prof. Dr. Y. Wang
Carbon Nano Materials Group, ZJU-NHU United R&D Center
Center for Chemistry of High-Performance and Novel Material
Key Lab of Applied Chemistry of Zhejiang Province
Department of Chemistry, Zhejiang University
Hangzhou, 310028 (P.R. China)
E-mail: chemwy@zju.edu.cn
Elemental analysis revealed the composition of CN-x (see
Table S1, Supporting Information), and the obtained materials
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cctc.201402561.
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
1
&
ÞÞ
These are not the final page numbers!

CHEMCATCHEM
COMMUNICATIONS
www.chemcatchem.org
much lower activities (Pd@CN-7: only 34% conver-
sion). The reaction was accelerated at higher temper-
ature (e.g., an increase from 30 to 558C increased the
conversion from 22 to 88% in 3 h; see Table 1, en-
tries 9 and 12). The time-active profiles for the selec-
tive hydrogenation of phenol over Pd@CN-1 at 35,
45, and 558C are shown in Figure S2. The Pd@CN-
1 catalyst proved to be stable with regard to oxida-
tion. The structure of the reused catalyst was charac-
terized by XRD and BET, and no significant change
before or after the use of the catalysts was observed
(Figures S3 and S4). Leaching of Pd into the product
solution was negligibly small (<0.1 ppm). Upon
using Pd@CN-1 for a second and third time, the conversions
were 80 and 91%.
Scheme 1. Ionic-liquid precursors used to synthesize the N-doped carbon materials.
were found to consist mainly of C and N. The N content of CN-
x is larger than 9.5 wt%, and the N content of CN-5 is as high
as 14.81 wt%. The textural properties of CN-x, including sur-
face area, pore size, and pore volume, are summarized in
Table S2 (Supporting Information); the surface areas range
from 487 to 714 m2 gÀ1, typical mesopore sizes of 4.6 to
13.8 nm are observed, and pore volumes of 0.64–1.52 cm3 gÀ1
were found for the CN-x catalysts in question.
Common Pd-based catalysts were tested under the same re-
action conditions for comparison (Table 1, entries 15–20). Com-
mercial Pd@C exhibited only 30% conversion of phenol in 3 h
at 558C. The conversions over Pd@MgO, Pd@g-Al2O3 and
Pd@mpg-C3N4 were 45, 42, and 44%, respectively, whereas
conversions of only 10 and 18% were obtained for Pd@CeO2
and Pd@TiO2, respectively, under the same reaction conditions.
To reveal the catalytic difference among the various Pd@CN-
x catalysts, further studies were performed. Particle size is
a possible factor that may influence catalytic activity. To ad-
dress the influence of the Pd particle size, TEM mages of
Pd@CN-1 and Pd@CN-7, which showed the best and worst ac-
tivities, respectively, were collected (Figure 1). Surprisingly, the
Pd nanoparticles on both carbon materials are very small, and
the average size is approximately 4 nm for both according to
the particle-size distributions (Figure 1b,d). Hence, the influ-
ence of Pd particle size is negligible in this case.
The activity of Pd@CN-x for the selective hydrogenation of
phenol was tested, and the results are presented in Table 1. In-
terestingly, all of the carbon materials were prepared similarly
and the textural properties are alike, but the catalytic activities
of Pd@CN-x were very different. For instance, Pd@CN-1 exhibit-
ed a conversion of 100% with 99% selectivity for cyclohexa-
none in 4 h at 458C, but the other seven catalysts showed
Table 1. Catalytic results for the selective hydrogenation of phenol.[a]
There are two oxidation states of the Pd species in the Pd
nanoparticles: Pd0 (metallic palladium) and Pd2+ (palladium
Entry
Catalyst
t [h]
T [8C]
Conv. [%]
Select. [%]
C=O
CÀOH
1
2
3
4
5
6
7
8
Pd@CN-1
Pd@CN-2
Pd@CN-3
Pd@CN-4
Pd@CN-5
Pd@CN-6
Pd@CN-7
Pd@CN-8
Pd@CN-1
Pd@CN-1
Pd@CN-1
Pd@CN-1
Pd@CN-1
Pd@CN-1
Pd@C
4
4
4
4
4
4
4
4
3
3
3
3
3
3
3
3
3
3
3
3
45
45
45
45
45
45
45
45
30
35
45
55
55
55
55
55
55
55
55
55
100
82
47
63
79
59
34
39
22
31
74
88
80
91
30
45
10
42
18
44
99
94
96
94
92
95
94
95
>99
>99
>99
98
99
99
98
98
97
99
1
6
4
6
8
5
6
5
<1
<1
<1
2
1
1
2
2
3
1
9
10
11
12
13[b]
14[c]
15
16
17
18
19
20
Pd@MgO
Pd@CeO2
Pd@g-Al2O3
Pd@TiO2
>99
>99
<1
<1
Pd@mpg-C3N4
[a] Reaction conditions: Phenol (0.585 mmol), Pd (4 mol% relative to
phenol), H2O (2 mL), H2 (0.1 MPa). [b] Pd@CN-1 was used for a second
time. [c] Pd@CN-1 was used for a third time.
Figure 1. TEM images of Pd@CN-1 (a,b) and Pd@CN-7 (c,d).
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
2
&
ÞÞ
These are not the final page numbers!

CHEMCATCHEM
COMMUNICATIONS
www.chemcatchem.org
oxide). As shown in Figure S5, analysis of the catalysts by Pd X-
ray photoelectron spectroscopy (XPS) revealed a doublet corre-
sponding to Pd3d5/2 and Pd3d3/2. The Pd3d5/2 peak at 336.2 eV
is attributed to Pd0, whereas the Pd3d5/2 peak at 338.5 eV is re-
lated to Pd2+. According to the XPS data, Pd0 is formed as the
major phase of Pd for Pd@CN-1 (71%), and the percentage of
Pd2+ is only 29%. However, for the other samples, the percent-
age of Pd0 is much lower; for example, the percentage of Pd0
in CN-5 is only 37%. The conversion of phenol into cyclohexa-
none versus the Pd0 content in the corresponding catalyst
were correlated and are shown in Figure 2. If the percentage
Table 2. Hydrogenation of substituted phenols.[a]
Entry Substrate
1
T [8C] t [h] Conv. [%] Product
Select. [%]
90
80
4
60
2
3
4
5
6
60
60
60
45
80
3.5 100
99
91
96
61
81
4
3
6
5
100
100
100
98
7
80
8
70
63
[a] Reaction conditions: Substrate (0.5 mmol), Pd (4.7 mol% relative to
substrate), H2O (2 mL), H2 (0.1 MPa).
Figure 2. Relationship between phenol conversion and percentage of Pd0 in
the Pd@CN-x catalyst.
genations with Pd@CN-1. As illustrated, 100% conversion was
achieved for m-cresol, p-cresol, and hydroquinone (Table 2, en-
tries 2–4), and the selectivities toward substituted cyclohexa-
nones were good (>91%). For o-cresol, the selectivity for
ketone was 90% and the conversion was 60% (Table 2,
entry 1). For resorcinol, the obtained main product was not hy-
droxylcyclohexanone (31%) but the reductive dehydration
product cyclohexanone (61%; Table 2, entry 5). A possible
route to its synthesis is presented in Scheme S2. For hydroge-
nations of catechol and p-tert-butylphenol, good to moderate
ketone selectivities of 81 and 63% were achieved at conver-
sions of 98 and 70%, respectively (Table 2, entries 6 and 7).
In conclusion, mesoporous N-doped carbon materials (CN-x)
were prepared from N-containing ionic-liquid precursors. The
obtained carbon materials were loaded with Pd nanoparticles
by the ultrasound-assisted method. The Pd@CN-x catalysts ex-
hibited outstanding conversion and cyclohexanone selectivity
for the selective hydrogenation of phenol to cyclohexanone
under mild conditions in water. However, the activities of
Pd@CN-x derived from various ionic liquids were different, and
investigations indicated that the percentage of Pd0 in the Pd
nanoparticles may be the key point. The Pd@CN-x catalysts
showed potential in the selective hydrogenation of substituted
phenol.
of Pd0 was low (<50%), the corresponding conversion of
phenol was not correlated with the percentage of Pd0, and this
may be because there are many other factors including the
properties of the support that influence the reaction. The per-
centage of Pd0 is not significant; for example, in Pd@CN-5, the
percentage of Pd0 is only 37%, but because other factors such
as the high surface area of the support (714 m2 gÀ1, Table S2),
the conversion was high (79%). If the percentage of Pd0 is
high, for example, for Pd@CN-1 in which the Pd0 percentage is
71%, the influence of Pd0 is significant and it becomes the de-
termining factor, so the conversion of phenol over Pd@CN-1 is
the highest.
It is interesting that the percentage of Pd0 on Pd@CN-x de-
rived from different ionic-liquid precursors is so different, and
the doped N atoms may be involved because of the electrone-
gativity and cloud density of the N atom. In comparison to tra-
ditional carbon materials, N-doped carbon materials show
better performance in the electrochemical fields, such as in the
oxygen reduction reaction, lithium batteries, and supercapaci-
tors.[19] Besides, the N atom in doped carbon materials can also
increase catalytic activity significantly, according to previous re-
ports.[15,16] Therefore, we investigated the N species of CN-x.
The samples were analyzed by XPS, as shown in Figure S6.
There are four kinds of N species in N-doped carbon with bind-
ing energies of approximately 398.8, 400.2, 401.5, and 404.0 eV,
which correspond to pyridine N, pyrrole N, quaternary N, and
N-oxide, respectively. The percentages of each N species are
summarized in Table S3. The N distributions of CN-x are very
different, and no clear conclusions can be made.
Experimental Section
Materials
All chemicals were used as received from the Aladdin Chemistry
Co., Ltd. Pd@C was obtained from ThalesNano. Pd@MgO, Pd@TiO2,
Pd@CeO2, and Pd@g-Al2O3 were synthesized according to literature
procedures.[20]
To illustrate the general applicability of the Pd@CN-x cata-
lysts, the method was extended to the hydrogenation of other
substituted phenols. Table 2 shows the results of these hydro-
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
3
&
ÞÞ
These are not the final page numbers!

CHEMCATCHEM
COMMUNICATIONS
www.chemcatchem.org
microscopy (TEM) images were obtained by using a JEM-1230 at
an accelerating voltage of 80 kV. The samples were suspended in
ethanol under ultrasound for 1 h and then dispersed onto a holey
carbon-coated Cu grid.
Syntheses
Ionic liquids: The eight ionic liquids were synthesized according to
the method reported in the literature.[21] Typically, solid AgNO3
(17.0 g, 0.1 mol) was dissolved in deionized water (100 mL); then,
NaN(CN)2 powder (8.9 g, 0.1 mol) was added into the AgNO3 aque-
ous solution with magnetic stirring. After 1 h of stirring, the solu-
tion was filtered, and white, solid AgN(CN)2 was obtained. 3-Pico-
line (46.6 g, 0.5 mol) was added into a 250 mL, three-necked flask,
and an equal stoichiometric amount of bromobutane (70.0 g,
0.5 mol) was placed in a pressure-equalizing dropping funnel and
added to the three-necked flask within 2 h at 1008C. After 12 h,
the mixture was cooled down to room temperature. It was then
dissolved in deionized water and washed with ethyl acetate (2ꢁ)
for purification before the water was removed by vacuum distilla-
tion. The purified ionic liquid N-butyl-3-methylpyridine bromide (3-
MBP-Br; 23.0 g, 0.1 mol) and AgN(CN)2 (0.1 mol) were mixed in de-
ionized water (150 mL) with magnetic stirring in the dark for 12 h.
The so-obtained mixture was then filtered, and the filtrate was
concentrated under reduced pressure. The other ionic liquids were
prepared similarly.
Catalytic ability test of phenol hydrogenation
In a typical reaction, phenol (55 mg, 0.585 mmol) and the Pd@CN-
x catalyst (25 mg, Pd 4 mol% relative to phenol) were placed into
a three-necked flask, and deionized water (2 mL) was added as the
solvent. Prior to the reaction, a balloon filled with hydrogen was
connected to the flask, and the air in the flask was replaced by hy-
drogen (3ꢁ). Then, the flask was placed in an oil bath at the de-
sired temperature and the reaction was started. Upon completion
of the reaction, the conversion and selectivity were determined by
GC–FID and the products were identified by GC–MS.
Acknowledgements
Financial support from the National Natural Science Foundation
of China (21376208 & U1162124), the Zhejiang Provincial Natural
Science Foundation for Distinguished Young Scholars of China
(LR13B030001), the Specialized Research Fund for the Doctoral
Program of Higher Education (J20130060), the Fundamental Re-
search Funds for the Central Universities, the Program for Zhe-
jiang Leading Team of S&T Innovation, the Partner Group Pro-
gram of the Zhejiang University, and the Max-Planck Society are
greatly appreciated.
N-Doped carbon materials, CN-x: The eight N-doped carbon mate-
rials were synthesized by the so-called hard-template method by
using ionic liquids as precursors and Ludox HS-40 colloidal silica as
the hard template. Typically, the ionic liquid (3.0 g) and Ludox HS-
40 colloidal silica (3.75 g) were mixed in a crucible and then cal-
cined in a muffle furnace at a programmed temperature over a N2
flow (400 mLminÀ1). The temperature program is shown in Fig-
ure S1. Initially, the temperature was increased from room temper-
ature to 3008C over 30 min, and then it remained at 3008C for 1 h.
After that, the temperature was increased to 9008C within 1 h and
remained there for another 1 h. After letting the crucible cool to
room temperature by turning off the heating device, a black solid
was obtained. The black solid was ground into a black powder and
transferred into a plastic bottle. NH4HF2 (60 g) and deionized water
(240 mL) were also added into the bottle. After magnetic stirring at
room temperature for 48 h and filtering the solution, a black solid
residue was obtained, which was dried in an oven overnight. The
black solid was then also ground into a black powder.
Keywords: doping · heterogeneous catalysis · hydrogenation ·
ionic liquids · phenol
[1] a) I. Dodgson, K. Griffin, G. Barberis, F. Pignataro, G. Tauszik, Chem. Ind.
1989, 830–833; b) M. T. Musser in Ullmann’s Encyclopedia of Industrial
Chemistry, Wiley-VCH, 2000.
[2] a) Y. Wang, J. S. Zhang, X. C. Wang, M. Antonietti, H. R. Li, Angew. Chem.
Int. Ed. 2010, 49, 3356–3359; Angew. Chem. 2010, 122, 3428–3431;
b) T. F. S. Silva, G. S. Mishra, M. F. G. da Silva, R. Wanke, L. Martins, A. J. L.
Pombeiro, Dalton Trans. 2009, 9207–9215; c) U. Schuchardt, D. Cardo-
so, R. Sercheli, R. Pereira, R. S. de Cruz, M. C. Guerreiro, D. Mandelli, E. V.
Spinace, E. L. Fires, Appl. Catal. A 2001, 211, 1–17; d) V. Z. Fridman, A. A.
Davydov, J. Catal. 2000, 195, 20–30.
[3] a) S. Watanabe, V. Arunajatesan, Top. Catal. 2010, 53, 1150–1152; b) T. T.
Yu, J. Q. Wang, X. M. Li, X. Q. Cao, H. W. Gu, ChemCatChem 2013, 5,
2852–2855.
Pd@CN-x: The Pd@CN-x catalysts were synthesized by a simple ul-
trasound-assisted method. Typically, CN-x (0.1 g) was dispersed in
deionized water (10 mL) in a beaker by ultrasound. Then, an aque-
ous solution of PdCl2 (0.01 gmLÀ1, 2 mL) was added into the
beaker. After treatment by ultrasound for 10 min, a solution of
NaBH4 (10 mg) in deionized water (5 mL) was added into the solu-
tion, and the mixture was kept in the ultrasound bath for another
30 min. Later, the solution was filtered, and the residue (black
solids) was washed with deionized water several times. Then, the
black solid was dried in an oven overnight and collected for the
catalytic test.
[4] a) H. J. Wang, F. Y. Zhao, S. I. Fujita, M. Arai, Catal. Commun. 2008, 9,
362–368; b) N. Mahata, V. Vishwanathan, J. Catal. 2000, 196, 262–270;
c) J. Morales, R. Hutcheson, C. Noradoun, I. F. Cheng, Ind. Eng. Chem.
Res. 2002, 41, 3071–3074.
[5] a) C. Park, M. A. Keane, J. Colloid Interface Sci. 2003, 266, 183–194; b) G.
Neri, A. M. Visco, A. Donato, C. Milone, M. Malentacchi, G. Gubitosa,
Appl. Catal. A 1994, 110, 49–59; c) S. G. Shore, E. R. Ding, C. Park, M. A.
Keane, Catal. Commun. 2002, 3, 77–84; d) P. Claus, H. Berndt, C. Mohr,
J. Radnik, E. J. Shin, M. A. Keane, J. Catal. 2000, 192, 88–97; e) Y. Perez,
M. Fajardo, A. Corma, Catal. Commun. 2011, 12, 1071–1074; f) S. Velu,
M. P. Kapoor, S. Inagaki, K. Suzuki, Appl. Catal. A 2003, 245, 317–331;
g) K. V. R. Chary, D. Naresh, V. Vishwanathan, M. Sadakane, W. Ueda,
Catal. Commun. 2007, 8, 471–477.
[6] a) J. R. Gonzalez-Velasco, M. P. Gonzalezmarcos, S. Arnaiz, J. I. Gutierre-
zortiz, M. A. Gutierrezortiz, Ind. Eng. Chem. Res. 1995, 34, 1031–1036;
b) C. M. Cirtiu, A. F. Dunlop-Briere, A. Moores, Green Chem. 2011, 13,
288–291; c) N. Mahata, K. V. Raghavan, V. Vishwanathan, C. Park, M. A.
Keane, Phys. Chem. Chem. Phys. 2001, 3, 2712–2719.
Characterization of CN-x and Pd@CN-x
The surface areas of the N-doped carbon materials were character-
ized by N2 adsorption–desorption isotherms at 77 K by using an
AUTOSORB-1. Samples were degassed at 1508C for 10 h until the
pressure was less than 10À4 Pa. Element analysis was used for the
N-doped carbon materials to measure the main elemental compo-
sition by using a Flash EA 1112, ThermoFinnigan. X-ray powder dif-
fraction analyses (XRD) were conducted with an Ultima TV X-ray
diffractometer with CuKa radiation (1.54 ꢂ). Samples were dried
overnight at 808C prior to characterization. Transmission electron
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
4
&
ÞÞ
These are not the final page numbers!

CHEMCATCHEM
COMMUNICATIONS
www.chemcatchem.org
[7] a) E. J. Shin, M. A. Keane, Ind. Eng. Chem. Res. 2000, 39, 883–892; b) M.
Ohde, H. Ohde, C. M. Wai, Chem. Commun. 2002, 2388–2389; c) Z. Q.
Guo, L. Hu, H. H. Yu, X. Q. Cao, H. W. Gu, RSC Adv. 2012, 2, 3477–3480;
d) Y. Motoyama, M. Takasaki, S. H. Yoon, I. Mochida, H. Nagashima, Org.
Lett. 2009, 11, 5042–5045; e) H. H. Duan, D. S. Wang, Y. Kou, Y. D. Li,
Chem. Commun. 2013, 49, 303–305.
[8] a) P. Makowski, R. D. Cakan, M. Antonietti, F. Goettmann, M. M. Titirici,
Chem. Commun. 2008, 999–1001; b) E. Dꢃaz, A. F. Mohedano, L. Calvo,
M. A. Gilarranz, J. A. Casas, J. J. Rodriguez, Chem. Eng. J. 2007, 131, 65–
71; c) C. V. Rode, U. D. Joshi, O. Sato, M. Shirai, Chem. Commun. 2003,
1960–1961.
[9] H. Y. Cheng, R. X. Liu, Q. Wang, C. Y. Wu, Y. C. Yu, F. Y. Zhao, New J.
Chem. 2012, 36, 1085–1090.
[10] H. Z. Liu, T. Jiang, B. X. Han, S. G. Liang, Y. X. Zhou, Science 2009, 326,
1250–1252.
[11] A. B. Chen, G. Y. Zhao, J. Z. Chen, L. M. Chen, Y. F. Yu, RSC Adv. 2013, 3,
4171–4175.
[12] J. Z. Chen, W. Zhang, L. M. Chen, L. L. Ma, H. Gao, T. J. Wang, ChemPlus-
Chem 2013, 78, 142–148.
[16] X. Xu, Y. Li, Y. T. Gong, P. F. Zhang, H. R. Li, Y. Wang, J. Am. Chem. Soc.
2012, 134, 16987–16990.
[17] a) J. S. Lee, X. Wang, H. Luo, G. A. Baker, S. Dai, J. Am. Chem. Soc. 2009,
131, 4596–4597; b) J. P. Paraknowitsch, J. Zhang, D. Su, A. Thomas, M.
Antonietti, Adv. Mater. 2010, 22, 87–92; c) J. S. Lee, X. Wang, H. Luo, S.
Dai, Adv. Mater. 2010, 22, 1004–1007; d) J. Yuan, C. Giordano, M. Anto-
nietti, Chem. Mater. 2010, 22, 5003–5012.
[18] P. F. Zhang, Y. T. Gong, H. R. Li, Z. R. Chen, Y. Wang, Nat. Commun. 2013,
4, 1593–1594.
[19] a) K. P. Gong, F. Du, Z. H. Xia, M. Durstock, L. M. Dai, Science 2009, 323,
760–764; b) A. L. M. Reddy, A. Srivastava, S. R. Gowda, H. Gullapalli, M.
Dubey, P. M. Ajayan, ACS Nano 2010, 4, 6337–6342; c) K. S. Kim, S. J.
Park, J. Electroanal. Chem. 2012, 673, 58–64; d) C. L. Han, J. Wang, Y. T.
Gong, X. Xu, H. R. Li, Y. Wang, J. Mater. Chem. A 2014, 2, 605–609; e) J.
Wang, Z. Xu, Y. T. Gong, C. L. Han, H. R. Li, Y. Wang, ChemCatChem 2014,
6, 1204–1209.
[20] U. R. Pillai, E. Sahle-Demessie, Green Chem. 2004, 6, 161–165.
[21] N. Papaiconomou, J. Estager, Y. Traore, P. Bauduin, C. Bas, S. Legeai, S.
Viboud, M. Draye, J. Chem. Eng. Data 2010, 55, 1971–1979.
[13] J. Y. Shin, D. J. Jung, S. G. Lee, ACS Catal. 2013, 3, 525–528.
[14] a) Y. Wang, J. Yao, H. R. Li, D. S. Su, M. Antonietti, J. Am. Chem. Soc.
2011, 133, 2362–2365; b) Y. Li, X. Xu, P. F. Zhang, Y. T. Gong, H. R. Li, Y.
Wang, RSC Adv. 2013, 3, 10973–10982.
Received: July 22, 2014
[15] Z. Li, J. Liu, C. Xia, F. Li, ACS Catal. 2013, 3, 2440–2448.
Published online on && &&, 0000
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
5
&
ÞÞ
These are not the final page numbers!

COMMUNICATIONS
X. Xu, H. Li, Y. Wang*
Being picky: N-Doped carbon (CN-x)
derived from N-containing ionic-liquid
precursors are used as Pd nanoparticle
supports for the selective hydrogena-
tion of phenol to cyclohexanone with
high activity and selectivity under mild
reaction conditions. The activities of the
Pd@CN-x catalysts derived from a variety
of ionic liquids are different, and studies
on the physical properties, Pd status,
and N species of the catalysts are per-
formed.
&& – &&
Selective Hydrogenation of Phenol to
Cyclohexanone in Water over Pd@N-
Doped Carbon Derived from Ionic-
Liquid Precursors
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ChemCatChem 0000, 00, 1 – 5
&
6
&
ÞÞ
These are not the final page numbers!