Preparation of a Cu-Ru/carbon nanotube catalyst for hydrogenolysis of glycerol to 1,2-propanediol via hydrogen spillover

Article abstract of DOI:10.1039/c0gc00809e

A Cu-Ru nanoparticle catalyst supported on carbon nanotubes was prepared by a chemical replacement reaction between Cu metal nanoparticles and Ru ³⁺ cations. The as-prepared catalyst was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H₂ and CO chemisorption, and transmission electron microscopy. The results showed that the highly dispersed Ru clusters were present on the external surface of the Cu particles. These tiny Ru clusters did not activate glycerol to carry its hydrogenolysis, but instead activated and generated active hydrogen, which was transferred to the Cu surface nearby via hydrogen spillover. The Cu-Ru catalyst exhibited selectivity for 1,2-propanediol that was as high as Cu metal, and much higher hydrogenolysis activity than pure Cu metal because of the hydrogen spillover effect, which benefited from the Ru clusters.

Full text of DOI:10.1039/c0gc00809e

View Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Green Chemistry
Cite this: Green Chem., 2011, 13, 1311
www.rsc.org/greenchem
PAPER
Preparation of a Cu–Ru/carbon nanotube catalyst for hydrogenolysis of
glycerol to 1,2-propanediol via hydrogen spillover†
Zhijie Wu, Yuzhen Mao, Xiaoxiao Wang and Minghui Zhang*
Received 14th November 2010, Accepted 28th January 2011
DOI: 10.1039/c0gc00809e
A Cu–Ru nanoparticle catalyst supported on carbon nanotubes was prepared by a chemical
replacement reaction between Cu metal nanoparticles and Ru3+ cations. The as-prepared catalyst
was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, H2 and CO
chemisorption, and transmission electron microscopy. The results showed that the highly
dispersed Ru clusters were present on the external surface of the Cu particles. These tiny Ru
clusters did not activate glycerol to carry its hydrogenolysis, but instead activated and generated
active hydrogen, which was transferred to the Cu surface nearby via hydrogen spillover. The
Cu–Ru catalyst exhibited selectivity for 1,2-propanediol that was as high as Cu metal, and much
higher hydrogenolysis activity than pure Cu metal because of the hydrogen spillover effect, which
benefited from the Ru clusters.
Group VIII metals, such as Ru metal catalysts,8 are well known
Introduction
to be very active in direct cleavage C–C and C–O bonds and be
Glycerol is an attractive resource because of its ample availability
active in the hydrogenolysis of glycerol. Unfortunately, Ru often
as a by-product formed in biodiesel production, and because it
promotes excessive C–C cleavage, resulting in a high selectivity
is a model compound that allows not only the exploration of
for hydrocarbons (mainly methane).6 Ru surface-modified by
its conversion to H2 and CO2, but also details of the chemical
sulfur has been reported to promote the selectivity for 1,2-
transformations to other alcohols, such as 1,2-propanediol (1,2-
propanediol by poisoning the active Ru sites and changing their
PDO) and 1,3-propanediol (1,3-PDO).1 It has been reported
selectivity towards the cleavage of C–C bonds.6
that glycerol can be converted to propanediols by hydrogenolysis
Another report on the poisoning of C–C bond hydrogenolysis
using heterogeneous catalysts.2 This reaction is currently widely
active sites describes the deposition of Ru clusters on the
studied because it is an important and appropriate probe for
surface of copper by the redox reduction of Cu metal with
studying the selective removal of excess hydroxyl groups present
in biofeedstocks (i.e., sugars and sugar alcohols), which is
RuCl3 solution. A new catalytic site, CuxRuyClz on the high
index planes of Cu, was formed and exhibited high activity
important for the formation of fuels and chemicals with lower
and selectivity.6 At present, bimetallic metal catalysts, especially
oxygen content.3,4
Cu metal catalysts generally possess a high selectivity for
Cu-based7 and Ru-based9 catalysts, have attracted increasing
interest for their ability to promote the performance of glycerol
producing 1,2-propanediol,5 because of their intrinsic ability to
hydrogenolysis.
selectively cleave the C–O bonds in preference to the C–C bonds
Recently, a highly active and selective Ru–Cu bimetallic
in glycerol,4 which is required for propylene glycol formation,
catalyst supported on clay has been reported for the hydrogenol-
suggesting higher hydrogenation activity toward C–O bond than
ysis of glycerol to 1,2-propanediol.10 The Ru–Cu catalyst was
hydrogenolysis activity.6 To increase the activity of Cu metal, Cu-
prepared by covering Ru metal with Cu metal by impregnation,
based bimetallic catalysts (Cu–Cr,7a,7b Cu–Al7c and Cu–Ag7d)
suggesting the requirement of modification of the Ru surface to
were developed to promote the cleavage of C–O bonds and
promote the selectivity. In our previous work, another route for
the hydrogen activation capability of Cu metal. By comparison,
the surface modification of metal nanoparticles with added met-
als has been studied by the chemical replacement method,11 and
the surface alloying/interaction of host metal and added metals
Institute of New Catalytic Materials Science, Department of Material
was revealed to promote the hydrogenation activity. In our view,
the surface modification of Cu nanoparticles by Ru metal may
combine the high selectivity of Cu metal and high hydrogenation
activity of Ru metal, which results in a good bimetallic catalyst
for glycerol hydrogenolysis. In addition, carbon materials are
Chemistry, College of Chemistry, and Key Laboratory of Advanced
Energy Materials Chemistry (MOE), Nankai University, Tianjin,
300071, China. E-mail: zhangmh@nankai.edu.cn; Fax: +86
22-2350-7730; Tel: +86 22-2350-7730
† Electronic supplementary information (ESI) available: Fig. S1 and
Table S1. See DOI: 10.1039/c0gc00809e
This journal is
The Royal Society of Chemistry 2011
Green Chem., 2011, 13, 1311–1316 | 1311
©

View Online
Table 1 The surface properties, metal loadings and metal dispersions of catalysts
Metal dispersion (dchem, nm)d
SBET (m2 g-1)
Vpore (cm3 g-1)
Dave (nm)
Metal loading (wt.%)
Ru
Cu
a
b
c
Sample
Ru/C
MWCNTs
Cu/MWCNTs
Cu/MWCNTse
Ru/MWCNTs
Cu–Ru/MWCNTs
—
—
—
5.0 (Ru)
—
37.6 (Cu)
15.0 (Cu)
5.0 (Ru)
0.19 (5.7)
—
—
—
0.27 (4.5)
0.89 (1.2)
—
—
135.8
96.7
110.6
124.2
96.4
0.31
0.19
0.24
0.24
0.17
10.8
10.4
10.8
10.9
10.5
0.29 (32.3)
0.55 (17.1)
—
28.4 (Cu), 4.8 (Ru)
0.51 (18.4)
a BET surface area calculated from the linear part of the BET plot. b Estimated using the adsorption branch of the isotherm by the BJH method.
c BJH average pore size (4 V/A). d Mean cluster sizes were estimated from metal dispersions by assuming spherical structures and values for the
atomic volume in bulk Ru (13.65¥ 10-3 nm3) and Cu (11.83¥ 10-3 nm3).22 e The catalyst was prepared by incipient wetness impregnation, dried at
373 K for 12 h, treated in dry air at 300 ◦C for 4 h, followed by H2 at 300 ◦C for 2 h.
a good support for hydrogenation catalysts because of their
excellent hydrogen adsorption,12 especially carbon nanotubes,
which have been regarded as a potential hydrogen storage
medium via hydrogen spillover.13 Here, we report a simple
route to the synthesis of carbon nanotube decorated with Cu–
Ru bimetallic nanoparticles for glycerol hydrogenolysis. In this
route, the Cu decorated carbon nanotubes were prepared by a
rapid, solventless, bulk preparation method,14 and Ru metal was
introduced by the chemical replacement method.
The Cu–Ru/MWCNTs show only the peaks corresponding to
Cu metal, and no reflections corresponding to Ru metal are
detected. This can be ascribed to the occurrence of highly
dispersed Ru species by the chemical replacement method,6,19
in which the Ru3+ cations selectively replace surface copper
atoms, especially the active sites (defects, vacancies, etc.),
resulting in discontinuous Ru metal species. However, a weak
peak corresponding to the (101) plane of Ru metal could be
distinguished in the XRD pattern of Ru/MWCNTs (JCPDS
No. 1-1253), suggesting larger Ru clusters. It is reasonable to
speculate that the Ru metal species should be selectively located
on the surface of Cu metal nanoparticles to generate tiny Ru
clusters.
Results and discussion
Catalyst characterization
Table 1 shows the surface properties of the catalysts. The
BET surface area, pore volume and pore size of MWCNTs
change a bit after the deposition of metal onto the supports. The
Cu/MWCNTs sample shows a muchlower surface area andpore
volume than Ru/MWCNTs, owing to the higher Cu metal load-
ing. After the replacement of Cu/MWCNTs with Ru3+, the re-
sulting Cu–Ru/MWCNTs catalyst exhibits a similar surface area
and pore properties to the Cu/MWCNTs. This indicates that the
deposition of Ru clusters should mainly occur on the surface of
Cu metal without any influence on the carbon surface. Moreover,
the dispersion of active Cu metal increases 76% after the replace-
ment (Table 1), which comes from the ~40% decrease of Cu
particle size as shown in Fig. 2. Compared to the Ru/MWCNTs
sample, the Cu–Ru/MWCNTs sample shows higher Ru metal
dispersion (1.6 times), suggesting that the Ru clusters are highly
dispersed on the surface via chemical replacement and the
capability of hydrogen activation is enhanced.14 Fig. 2 shows the
transmission electron microscope (TEM) images of the support
and metal catalysts. Most of the Ru, Cu and Cu–Ru particles
are located on the external surface of the MWCNTs without
incorporating clusters into the pores of MWCNTs. ~35 nm Cu
particles are highly dispersed over the surface of MWCNTs, and
smaller Ru particles (~5 nm) are also distributed homogeneously
in the Ru/MWCNTs samples. After the deposition of Ru by
the chemical replacement between Cu nanoparticles and Ru3+
cations, the size of Cu–Ru particles decreases to ~20 nm. The
location of Ru on the surface of Cu nanoparticles is confirmed by
the EELS mapping and EDS analysis (Fig. S1†). As confirmed
by the chemisorption results (Table 1), the decrease of particle
size after replacement results in a higher Cu metal dispersion.
The structure of catalysts was characterized by the X-ray
diffraction (XRD) patterns as shown in Fig. 1. Two broad and
featureless peaks at 2q = 26 and 43◦ are observed in the XRD
pattern of the multi-wall carbon nanotubes (MWCNTs). For
the Cu/MWCNTs sample, the peaks at 2q = 43, 50 and 74◦
correspond to the presence of Cu metal (JCPDS No. 1-1241).
Fig. 1 XRD patterns of samples.
1312 | Green Chem., 2011, 13, 1311–1316
This journal is
The Royal Society of Chemistry 2011
©

View Online
Fig. 2 TEM images and particle size distribution graphs of metal (Cu and Cu–Ru) clusters. The surface-area-weighted particle size distribution,
d
TEM, was calculated from dTEM = Rnidi3/Rnidi2.11c
In our previous work, the surface alloying effect or surface
1-propanol, 2-propanol, ethanol and methanol were detected
interaction between added metals and host metals occurred in
bimetallic nanoparticles prepared by the chemical replacement
method.11 Here, the surface interaction between Ru and Cu
metal was measured by the X-ray photoelectron spectroscopy
(XPS) characterization. Fig. 3 shows the XPS spectra of
Ru/MWCNTs, Cu/MWCNTs and Cu–Ru/MWCNTs samples.
The binding energies of Ru in Ru/MWCNTs are 280.5 eV (Ru
3d5/2), 461.7 eV (Ru 3p3/2) and 484.1 eV (Ru 3p1/2), suggesting the
presence of elemental Ru at the external surface of catalyst.10,15
The binding energies of Cu in Cu/MWCNTs are 932.8 eV (Cu
2p3/2) and 952.6 eV (Cu 2p1/2), corresponding to the presence
of surface metallic Cu species.16 The binding energy of C
1s (284.7 eV) on Ru/MWCNTs is the same as that of Cu/
MWCNTs. For the Cu–Ru/MWCNTs catalyst, the binding
energies of Ru, Cu and C do not shift compared with Cu/
MWCNTs and Ru/MWCNTs, suggesting no obvious surface
interaction of Ru and Cu occurs after the replacement.
in the liquid products, and CH4 was the main product in the
gas phase. When Ru/C and Ru/MWCNTs catalysts were used
(Table 2), the conversions of glycerol were 55.7% and 65.5%,
respectively. For both Ru metal catalysts, cleavage of C–C
bonds was observed, and CH4 was detected as the main gas
product, the yield of liquid product being ~70%. In addition,
the content of EG in the liquid product was 7–15%, which is
high compared with the results using Cu and Cu–Ru catalysts
(listed in Table 2). EG is formed by cleavage of the C–C bond,
further demonstrating that Ru is active in the cleavage of the
C–C bonds, which is in agreement with the work of other
groups.6 In contrast, the Cu/MWCNTs catalyst exhibited lower
hydrogenolysis rate and conversion of glycerol (31.3%), but
~100% yield of liquid product, and an especially high selectivity
for 1,2-PDO (Table 2), indicating that Cu catalysts have poor
activity towards C–C bond cleavage and good activity towards
C–O bond hydrogenation. For Cu catalysts with different Cu
crystallite sizes ranging from 32 to 17 nm (Table 1), their
activities tended to increase inversely from 1.2 ¥ 10-3 to 1.8 ¥
Catalytic performance
10-3 molglycerol mol-1
s-1 (Table 2), suggesting the size
surface-metal
requirement of active sites in which the high hydrogenolysis
activity occurs on the large clusters. When the Cu/MWCNTs
Table 2 summarizes the results of glycerol hydrogenolysis. For
the hydrogenolysis of glycerol, 1,2-PDO, ethylene glycol (EG),
This journal is
The Royal Society of Chemistry 2011
Green Chem., 2011, 13, 1311–1316 | 1313
©

View Online
the Cu–Ru/MWCNTs catalysts, it is interesting to find that
the conversion of glycerol increases by ~60% compared with
Ru/MWCNTs, and 99.7% yield of liquid product and 86.5%
selectivity to 1,2-PDO were found, which are close to that of Cu
metals.
Discussion
For the glycerol hydrogenolysis, unsaturated species adsorbed on
Cu undergo nucleophilic attack, which lead to dehydroxylation
(C–O cleavage), and retro-Michael (C–C cleavage) reactions.
The latter reaction makes it possible to obtain the selective
conversion of glycerol to ethanol and glycols, but it is always less
competitive than dehydroxylation.4,6 Therefore, the Cu catalyst
shows high selectivity for the dehydroxylation products (1,2-
PDO, 1-propanol, 2-propanol) as shown in Table 2.1,2 On the
other hand, the C–C bond hydrogenolysis on Ru metal could
easily lead to the C2 and C1 products, and higher selectivities of
ethanol, methanol and methane are observed on Ru catalysts.
As confirmed by XPS characterization above, no obvious
interaction of Cu and Ru occurred in the Cu–Ru/MWCNTs
catalyst, suggesting that the Ru and Cu could not greatly
influence the hydrogenolysis properties of each other. The high
yield of liquid product and 1,2-PDO selectivity (Table 2) on Cu–
Ru catalyst are generated by the Cu metal, because the Cu metal
is not able to hydrogenolyze C–C and C–O bonds, but presents
hydro-dehydrogenating properties toward C–O bonds.4,6 The Ru
metal shows high activity of C–C cleavage reactions (Table 2),
resulting in high yield of CH4. The results show that the
hydrogenolysis of glycerol should not directly occur on Ru metal
of Cu–Ru/MWCNTs catalyst.
The hydrogenolysis of glycerol reaction has been regarded as
a structure-sensitive reaction.4,17,18 The activity is dependent on
the particle size, and large Cu crystallites4 and Ru crystallites
(Table S1†) generally exhibit a high glycerol hydrogenolysis rate.
The Cu–Ru catalyst was prepared by the chemical replacement
method, suggesting that the size of Ru clusters is influenced
by the Cu particle sizes because the Ru species are located
on the surface of Cu nanoparticles.11c For metal nanoparticles,
the facets with different surface free energies show different
activities for the metal ions replacement during the chemical
replacement reaction.19 This indicates that, to deposit the Ru on
the Cu metal surface by replacement, the dissolution of Cu and
the deposition of Ru could not occur uniformly on the surface
of Cu particles. This makes it difficult to obtain a continuous
Ru film or large Ru clusters on the surface of Cu particles,
suggesting that the Cu acts as the diluting element to inhibit the
growth of Ru particles/film. This dilution selectively poisons the
hydrogenolysis reaction, which requires relatively large clusters
or ensembles of adjacent Ru atoms.20 The highly dispersed Ru
metal species at the external surface of Cu particles make it to
difficult to adsorb (and activate) glycerol in the hydrogenolysis
reaction.
Fig. 3 XPS spectra of samples.
and Ru/MWCNTs were mixed together and used to catalyze
the hydrogenolysis, about 10% increase of glycerol conversion
occurred relative to Ru/MWCNTs, and 73.7% yield of liquid
and 74.2% selectivity of 1,2-PDO were found, which is similar
to that of the Ru/MWCNTs. This suggests the Ru/MWCNTs
contributed the most activity in the mixture of catalysts. For
Compared to the Cu/MWCNTs, the derived Cu–Ru catalyst
shows more than double the hydrogenolysis rate (turnover rate,
TOR) and conversion of glycerol. For the replacement of Cu
metal with Ru3+ ions, the particle size of Cu particles decreases by
~45%, resulting in an increase of 30% of the amount of surface-
active Cu metal per gram of catalyst. On the other hand, the
1314 | Green Chem., 2011, 13, 1311–1316
This journal is
The Royal Society of Chemistry 2011
©

View Online
Table 2 Glycerol hydrogenolysis rates, conversion, yields and selectivities
Selectivities of liquid product (mol%)
TOR (10-3 mol
Conversion (%) mol-1 s-1)a yield (%) 1,2-Propanediol 1-Propanol 2-Propanol Glycol Ethanol Methanol
Liquid
Sample
surface-metal
Ru/C
55.7
31.3
15.5
65.5
77.2
61.1 (Ru)
1.8 (Cu)
1.2 (Cu)
55.2 (Ru)
60.6 (Ru)
71.3
~100b
~100
72.2
73.7
59.4
91.1
90.7
71.2
74.2
5.8
3.2
3.5
7.5
2.2
2.0
4.0
3.2
3.2
1.5
15.7
0.2
0.1
7.6
9.6
1.1
0.2
0.1
2.2
3.4
16.0
0.5
0.1
8.3
9.1
Cu/MWCNTs
Cu/MWCNTsc
Ru/MWCNTs
Cu/MWCNTs +
Ru/MWCNTsd
Cu–Ru/MWCNTs 99.8
3.9 (Cu)
99.7
86.5
10.4
2.9
0.1
0
0.1
a Reaction activities were reported as the turnover rate (TOR) at ~5% conversion of glycerol, which is defined as the molar glycerol conversion rates
per mole of surface metal atoms (estimated from surface titration by CO and H2 gas described above). b The gas product of hydrocarbons is under
the detection limit of the TCD detector of GC. c The catalyst was prepared by incipient wetness impregnation, dried at 373 K for 12 h, treated in dry
air at 300 ◦C for 4 h, followed by H2 at 300 ◦C for 2 h. d The catalyst was prepared by manual mixing of Cu/MWCNTs and Ru/MWCNTs using a
mortar and pestle. The mounts of Cu and Ru used in the mixture are the same as those in the Cu–Ru/MWCNTs sample.
Cu–Ru catalyst also shows much higher (~3 times, in Table 2)
TOR than that of Cu/MWCNTs with similar metal crystallite
sizes (~20 nm in Table 1). These results show that the high
increase in conversion and TORs after deposition of Ru on the
surface of Cu metal does not mainly result from the decrease of
Cu particle size, and the presence of highly dispersed Ru metal
should play a more important role. Although the Ru on the Cu–
Ru cannot activate the glycerol molecules, it clearly dissociates
the hydrogen molecule to active hydrogen atoms, which is
confirmed by the hydrogen chemisorption result (Table 1). In
the hydrogenolysis of glycerol on Cu–Ru catalyst, the presence
of Ru acts as a route for the spillover of hydrogen toward
the major catalytic component, Cu, making it a highly active
catalyst.21 The use of spillover hydrogen has also been reported
by Zhou et al.,7d in which the hydrogen was activated by Ag
metal to reduce CuO into active Cu metal. Here, the hydrogen
activated by Ru metal diffuses over Cu metal surface nearby,
which increases the concentration of active hydrogen accessing
the adsorbed glycerol molecule.
Experimental
Chemicals
Multi-walled carbon nanotubes (MWCNTs, diameter
15~45 nm) were obtained from Xiamen University. Copper(II)
acetate (98%), ruthenium trichloride (99.995%) and 5 wt.%
Ru/carbon catalysts were purchased from KRS Fine Chemical
Co. Ltd (Tianjin, China), and used as received.
Catalyst preparation
The synthesis of Cu nanoparticle-decorated MWCNTs followed
the work of Lin.14 In a typical manual mixing experiment with
10 mol% Cu loading, MWCNTs (1.0 g, ~0.083 mole carbon
equivalent) were dry-mixed with powdered Cu(OAc)2·H2O
(1.8 g, ~9 mmol) using a mortar and pestle until homogenous (30
min) under ambient conditions. The solid Cu(OAc)2/MWCNT
mixture was then transferred to a glass vial and heated in an
Ar flow (100 cm-3 g-1 min-1) to 300 ◦C with a ramping rate
◦
of 2 C min-1, and held isothermally for 3 h. The product
In the present work, highly dispersed Ru clusters on Cu
nanoparticles have been prepared by the chemical replacement
method using Cu nanoparticles and Ru3+ ions. The resulting
Ru metal clusters provide active hydrogen on the surface of the
Cu nanoparticles, increasing the hydrogenolysis activity of Cu
metal.
(Cu/MWCNTs) was then collected without exposing it to air.
The Ru–Cu/MWCNTs was prepared by the replacement
method based on our previous work.11 In a typical experiment,
the freshly prepared Cu/MWCNTs (without contact with air)
was added to the 0.01 mol L-1 RuCl3 solution under flowing
Ar gas (40 cm-3 g-1 min-1). After replacement, the sample was
washed thoroughly until no Cl- was detected using 0.1 mol L-1
AgNO3 solution. The collected sample was dried in an Ar flow
(100 cm-3 g-1 min-1) at 80 ◦C for 12 h, and ◦then treated in a
20% H2/Ar flow (100 cm-3 g-1 min-1) at 300 C for 1.0 h. The
Ru loading was selected as 5 wt.%. For comparison, 5 wt.%
Ru/MWCNTs was prepared by incipient wetness impregnation
of aqueous RuCl3 solutions onto MWCNTs. The sample was
treated in an air flow (100 cm-3 g-1 min-1) at 300 ◦C for 3 h and
subsequently reduced under 20% H2/Ar flow (100 cm-3 g-1 min-1)
at 300 ◦C for 2 h.
Conclusions
The nanotube-supported Cu–Ru nanoparticles were prepared
by the chemical replacement method, in which the Ru species
were located on the external surface of Cu nanoparticles.
The deposition of Ru on the surface of Cu particle reduced
the Cu particle size and promoted the hydrogen activation
ability of Cu metal. Although the Ru in Cu–Ru could not
catalyze the hydrogenolysis of glycerol, it acted as a route for
hydrogen spillover. The resulted Cu–Ru catalyst showed higher
1,2-PDO selectivity than that of the Ru catalyst, and better
activity than the Cu catalyst. This study shows that chemical
replacement is a powerful method to prepare catalysts with
high activity and selectivity by the surface modification of metal
nanoparticles.
Catalyst characterization
The chemical compositions of the samples were analyzed by
inductively coupled plasma atomic emission spectrometry (ICP-
AES) on an IRIS Intrepid spectrometer. The XRD patterns
This journal is
The Royal Society of Chemistry 2011
Green Chem., 2011, 13, 1311–1316 | 1315
©

View Online
of reduced samples were recorded on a Rigaku D/max 2500
2 J. Sabadie, D. Barthomeuf, H. Charcosset and G. Descotes, Bull. Soc.
Chim. Fr., 1981, 7–8, 288.
3 A. Wawrzetz, B. Peng, A. Hrabar, A. Jentys, A. A. Lemonidou and
J. A. Lercher, J. Catal., 2010, 269, 411.
˚
X-ray diffractometer (Cu-Ka, l = 1.54178 A). TEM images were
acquired using a FEI Tecnai G2 high-resolution transmission
electron microscope operating at 200 kV. X-ray photoelectron
spectroscopy (XPS) analysis of the catalysts was carried out
using a Kratos Axis Ultra DLD spectrometer employing a
monochromatic Al-Ka source, hybrid magnetic/electrostatic
optics, and a multi-channel plate and delay line detector (DLD).
The surface of the samples was etched with Ar+ ions for
10 min prior to removing the oxidized layer. The specific surface
areas, average pore volume, and pore size distribution were
measured by N2 adsorption/desorption with the BET method
on a Microneritics ASAP 2010 C analyzer. The dispersion of
metal crystallites Ru was measured using H2 chemisorption
(ASAP2020, Micromeritics) at 40 ◦C and 5.0–50 kPa. Samples
were first treated in pure H2 for 1 h at 300 ◦C and then in a
dynamic vacuum for 1 h at 300 ◦C. The Cu metal dispersion was
4 S. Wang, Y. Zhang and H. C. Liu, Chem. Asian J., 2010, 5, 1100.
5 (a) M. Balaraju, V. Rekha, P. S. S. Prasad, R. B. N. Prasad and N.
Lingaiah, Catal. Lett., 2008, 126, 119; (b) L. Huang, Y. L. Zhu, H. Y.
Zheng, Y. W. Li and Z. Y. Zeng, J. Chem. Technol. Biotechnol., 2008,
83, 1670–1675; (c) Z. W. Huang, F. Cui, H. X. Kang, J. Chen and C.
G. Xia, Appl. Catal. A, 2009, 366, 288; (d) L. Y. Guo, J. X. Zhou, J.
B. Mao, X. W. Guo and S. G. Zhang, Appl. Catal. A, 2009, 367, 93;
(e) S. Sato, M. Akiyama, K. Inui and M. Yokota, Chem. Lett., 2009,
38, 560; (f) Q. J. Yu, X. H. Ma, Z. Lan, M. Z. Wang and C. J. Yu,
J. Phys. Chem. C, 2009, 113, 6969; (g) A. Bienholz, F. schwab and P.
Claus, Green Chem., 2010, 12, 290.
6 (a) J. Barbier, J. C. Menezo, C. Montassier, J. Naja, G. D. Angel
and J. M. Dominguez, Catal. Lett., 1992, 14, 37; (b) C. Montassier,
J. C. Menezo, J. Moukolo, J. Naja, L. C. Hoang, J. Barbier and J.
P. Boitiaux, J. Mol. Catal., 1991, 70, 65; (c) C. Montassier, J. C.
Menezo, L. C. Hoang, C. Renaud and J. Barbier, J. Mol. Catal.,
1991, 70, 99; (d) C. Montassier, J. C. Menezo, J. Naja, J. Barbier, J.
M. Dominguez, P. Sarrazin and B. Didillon, J. Mol. Catal., 1994, 91,
107; (e) C. Montassier, J. C. Menezo, J. Naja, J. Barbier, J. M. Domin-
guez, P. Sarrazin and B. Didillon, J. Mol. Catal., 1994, 91, 119.
7 (a) C. H. Liang, Z. Q. Ma, L. Ding and J. S. Qiu, Catal. Lett., 2009,
130, 169; (b) N. D. Kim, S. Oh, J. B. Joo, K. S. Jung and J. Yi,
Top. Catal., 2010, 53, 517; (c) R. B. Mane, A. M. Hengne, A. A.
Ghalwadkar, S. Vijayanand, P. H. Mohite, H. S. Potdar and C. V.
Rode, Catal. Lett., 2010, 135, 141; (d) J. X. Zhou, L. Y. Guo, X. W.
Guo, J. B. Mao and S. G. Zhang, Green Chem., 2010, 12, 1835.
8 (a) E. P. Maris and R. J. Davis, J. Catal., 2007, 249, 328; (b) T.
Miyazawa, S. Koso, K. Kunimori and K. Tomishige, Appl. Catal.
A, 2007, 329, 30; (c) T. Miyazawa, S. Koso, K. Kunimori and K.
Tomishige, Appl. Catal. A, 2007, 318, 244; (d) M. Balaraju, V. Rekha,
B. Devi, R. B. N. Prasad, P. S. S. Prasad and N. Lingaiah, Appl. Catal.
A, 2010, 384, 107; (e) L. Zhao, J. H. Zhou, Z. J. Sui and X. G. Zhou,
Chem. Eng. Sci., 2010, 65, 30.
9 (a) E. P. Maris, W. C. Ketchie, M. Murayama and R. J. Davis, J.
Catal., 2007, 251, 281; (b) L. Ma and D. H. He, Top. Catal., 2009,
52, 834.
10 T. Jiang, Y. X. Zhou, S. G. Liang, H. Z. Liu and B. X. Han, Green
Chem., 2009, 11, 1000.
11 (a) Z. J. Wu, M. H. Zhang, Z. F. Zhao, W. Li and K. Y. Tao, J. Catal.,
2008, 256, 323; (b) Z. F. Zhao, Z. J. Wu, L. X. Zhou, M. H. Zhang,
W. Li and K. Y. Tao, Catal. Commun., 2008, 9, 2191; (c) Z. J. Wu, Z.
F. Zhao and M. H. Zhang, ChemCatChem, 2010, 2, 1606.
12 L. Chen, A. C. cooper, G. P. Pez and H. S. Cheng, J. Phys. Chem. C,
2007, 111, 18995.
13 (a) J. M. Planeix, N. Coustel, J. Coq, V. Brotons, P. S. Kumbhar,
R. Dutartre, P. Geneste, P. Bernier and P. M. Ajayan, J. Am. Chem.
Soc., 1994, 116, 7935; (b) A. J. Lachawiec Jr., G. Qi and R. T. Yang,
Langmuir, 2005, 21, 11418.
◦
measured by the CO chemisorptions at 40 C and 5.0–50 kPa.
Metal dispersions were calculated by assuming H/Rus = 1 and
CO/Cus = 1 stoichiometries. Mean cluster sizes were estimated
from these dispersions by assuming spherical structures and
values for the atomic density in bulk Ru (13.65 ¥ 10-3 nm3)
and Cu (11.83 ¥ 10-3 nm3).22
Glycerol hydrogenolysis
The glycerol hydrogenolysis reaction was carried out in a 100 mL
stainless steel autoclave at a stirring speed of 800 rpm. 16 g
glycerol diluted with 4 mL deionized water (80 wt.% glycerol
in the aqueous solution) and 0.8 g catalyst was added to the
autoclave. The reactor was sealed and purified repeatedly with
hydrogen to eliminate air. Then the reactor was heated to the
reaction temperature (200 ◦C) and pressurized to 4.0 MPa. After
6 h, the reactor was cooled to room temperature. The liquid-
phase products were analyzed by a gas chromatograph with a
capillary column PEG 20 M (40 m ¥ 3 mm ¥ 0.25 mm) and a
flame ionization detector (FID). The gas products were detected
by using a thermal conductivity detector (TCD). Conversion of
glycerol is defined as the ratio of the number of moles of glycerol
consumed in the reaction to the total moles of glycerol initially
added. Yield of liquid product is defined as the ratio of the num-
ber of moles of glycerol consumed to produce the liquid product
to the number of moles of converted glycerol. The composition
of liquid product was calculated based on the number of C-based
moles of each component in the liquid product.
14 Y Lin, K. A. Watson, M. J. Fallbach, S. Ghose, J. G. Smith Jr., D. M.
Delozier, W. Cao, R. E. Crooks and J. W. Connell, ACS Nano, 2009,
3, 871.
15 R. Koetz, H. J. Lewrenz and S. Stucki, J. Electrochem. Soc., 1983,
130, 825.
16 J. Hedman, M. Klasson, R. Nilsson, C. Nordling, M. F. Sorokina,
O. I. Kljushnikov, S. A. Nemnonov, V. A. Trapeznikov and V. G.
Zyranov, Phys. Scr., 1971, 4, 195.
Acknowledgements
17 A. Marinoiu, G. Ionita, C. L. Ga´spa´r, C. Cobzaru and S. Oprea,
React. Kinet. Catal. Lett., 2009, 97, 315.
18 T. Miyazawa, S. Koso, K. Kunimori and K. Tomishige, Appl. Catal.
A, 2007, 18, 244.
The present work was supported by the Natural Sciences
Foundation of Tianjin (10JCYBJC04400) and MOE (IRT-
0927).
19 Q. B. Zhang, J. P. Xie, J. Y. Lee, J. X. Zhang and C. Boothroyd, Small,
2008, 4, 1067.
20 (a) Z. J. Wu, S. H. Ge, M. H. Zhang, W. Li, S. C. Mu and K. Y. Tao,
J. Phys. Chem. C, 2007, 111, 8587; (b) Z. J. Wu, M. H. Zhang, W. Li,
S. C. Mu and K. T. Tao, J. Mol. Catal. A, 2007, 273, 277.
21 T. Inui, Y. Ono, Y. Takagi and J. b. Kim, Appl. Catal. A, 2000, 202,
215.
22 G. Bergeret and P. Gallezot, ‘Character 3.1.2 Particle Size and
Dispersion Measurements’, in Handbook of Heterogeneous Catalysis,
ed. G. Ertl, H. Knozinger, F. Schuth and J. Weitkamp, Wiley-VCH,
2008, pp. 738–745.
References
1 (a) J. N. Chheda, G. W. Huber and J. A. Dumesic, Angew. Chem.,
Int. Ed., 2007, 46, 7164; (b) C. H. Zhou, J. N. Beltramini, Y. X. Fan
and G. Q. Lu, Chem. Soc. Rev., 2008, 37, 527; (c) A. Brandner, K.
Lehnert, A. Bienholz, M. Lucas and P. Claus, Top. Catal., 2009, 52,
278; (d) D. A. Simonetti and J. A. Dumesic, Catal. Rev. Sci. Eng.,
2009, 51, 441; (e) Y. Gu and F. Je´roˆme, Green Chem., 2010, 12, 1127;
(f) F. Je´roˆme, Y. Pouilous and J. Barrault, ChemSusChem, 2010, 1,
586.
1316 | Green Chem., 2011, 13, 1311–1316
This journal is
The Royal Society of Chemistry 2011
©