Tailored mesoporous copper/ceria catalysts for the selective hydrogenolysis of biomass-derived glycerol and sugar alcohols

Article abstract of DOI:10.1039/c5gc01766a

The selective hydrogenolysis of sugar alcohols is a promising means to produce valuable products from renewable biomass resources. The previous Cu-based catalysts generally suffer from low activity and/or poor stability. We report the design and fabrication of a tailored mesoporous copper/ceria catalyst by a one-step solid-state grinding-assisted nanocasting method. This new catalyst truly replicated the morphology and mesoporous structure of the silica template such as SBA-15 and KIT-6. The characterization techniques strongly reflected that Cu²⁺ was successfully substituted into the CeO₂ lattice and Cu nanoparticles were homogenously dispersed in the nanocomposite. This copper/ceria catalyst was highly active (TOF 4.8 h^-1) and stable for 300 h in the hydrogenolysis of glycerol to 1,2-propanediol. The excellent catalytic performance is due to monodisperse Cu nanoparticles, strong interaction between Cu and CeO₂ species, and tailored mesoporous structure.

Full text of DOI:10.1039/c5gc01766a

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Tailored mesoporous copper/ceria catalysts for selective
hydrogenolysis of biomass-derived glycerol and sugar alcohols†
∗
a
b
a,b
a,b
Shanhui Zhu, Xiaoqing Gao, Yulei Zhu, and Yongwang Li
a
State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese
Academy of Sciences, Taiyuan 030001, PR China
b
Synfuels China Co. Ltd., Taiyuan 030032, PR China
1
1
1
1
1
∗Corresponding author: State Key Laboratory of Coal Conversion, Institute of Coal
Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China.
Eꢀmail address: zhushanhui@sxicc.ac.cn
†Electronic supplementary information (ESI) available.
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Abstract: The selective hydrogenolysis of sugar alcohols is a promising means to
produce valuable products from renewable biomass resources. The previous Cuꢀbased
catalysts generally suffer from low activity and/or poor stability. We report the design
and fabrication of a tailored mesoporous copper/ceria catalyst by oneꢀstep solidꢀstate
grindingꢀassisted nanocasting method. This new catalyst truly replicated the
morphology and mesoporous structure of the silica template, such as SBAꢀ15 and
2
+
KITꢀ6. The characterization techniques strongly reflected that Cu was successfully
substituted into the CeO lattice and Cu nanoparticles were homogenously dispersed
2
ꢀ1
in the nanocomposite. This copper/ceria catalyst was highly active (TOF 4.8 h ) and
stable for 300 h in glycerol hydrogenolysis to 1,2ꢀpropanediol. The excellent catalytic
performance is due to monodisperse Cu nanoparticles, strong interaction between Cu
1
1
1
1
and CeO
2
species, and tailored mesoporous structure.
2

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1. Introduction
2
With declining fossil resources and rising CO emissions, significant efforts have
1
been devoted to the utilization of renewable resources, such as biomass. One of the
critical challenges in converting biomass into chemicals and fuels is to selectively
cleave C−O linkages of highly functionalized molecules to lower the oxygen content.
Sugar alcohols, such as glycerol, xylitol and sorbitol, are important platform
molecules and can be readily available in huge amounts from biodiesel process or
2
ꢀ4
lignocellulose.
Currently, deoxydehydration reaction has been effectively
developed to eliminate two hydroxyl groups from vicinal diols to afford alkenes by
5
ꢀ7
1
1
1
1
1
1
1
1
1
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2
2
2
various Reꢀbased catalysts. For example, glycerol was mainly converted to ally
3 3
alcohol while glucose was primarily yielded hexatriene over [CH ReO ] via
5
deoxydehydration method. Additionally, selective hydrogenolysis strategy offers a
promising possibility because this approach can be used to highꢀyield produce a wide
range of useful chemicals with low oxygen content. Moreover, hydrogenolysis holds
the great potential to bridge currently available petroleumꢀtechnologies and future
2
biomass refinery process. For example, 1,2ꢀpropanediol (1,2ꢀPDO) is an important
precursor of polyester resin and pharmaceutical, which can be synthesized by
8ꢀ15
16
selective hydrogenolysis of glycerol primary C−O bond.
Huber et al. have
reported the aqueousꢀphase hydrogenolysis of sorbitol to valuable alkanes and
17
oxygenates with Pt/SiO
(EG, 32.4%) and 1,2ꢀPDO (24.9%) from xylitol hydrogenolysis over Ru/C in the
presence of Ca(OH)
2 2 3
ꢀAl O . Liu et al. achieved high yields of ethylene glycol
2
.
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Among the catalysts for catalytic sugar alcohol hydrogenolysis, noble metal (e.g.,
Pt, Ru, Pd) have been employed extensively owing to their high activity and
18ꢀ28
stability.
Nevertheless, the expensive cost and limited availability of them have
necessitated the development of base catalysts with earthꢀabundant elements, such as
Fe, Ni and Cu. Copperꢀbased catalysts, if designed elaborately, may be potential
alternative to precious metals for its intrinsic ability to cleave C−O bond
8
,29
selectively.
Nevertheless, copper nanoparticles are susceptible to irreversible
30
deactivation via sintering owing to the low melting point and Tammann temperature.
Some effective strategies to confine particle growth have been established, such as
alloying, regulating pore structure, fabricating core shell material, creating conformal
coatings by atomic layer deposition, increasing metalꢀsupport interaction and
1
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1
1
1
2
2
2
31ꢀ34
optimizing interfacial area.
Recently, the encapsulation of individual nanoparticles
in morphologically wellꢀdefined inorganic tubes or shell has also gained considerable
35
interest owing to the outstanding thermal and chemical stability in catalysis.
Nanocasting is also called hard templating method, and has emerged as a highly
powerful approach for producing encapsulated nanoparticles in tailored nonꢀsilica
36ꢀ38
mesoporous tube or ordered pore.
Although the mesoporous material from
nanocasting has lower orderliness than conventional soft templating method, it
endows abundant surface defects and is beneficial for improving the catalytic
3
2
performance. Tao et al. incorporated Au nanoparticles into mesoporous CeO
(mpꢀCeO ) to synthesize highly active Au@mpꢀCeO in waterꢀgas shift reaction by
postꢀsynthetic method; mpꢀCeO
2
2
2
2
was first made by nanocasting method in which
4

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3 3 2
Ce(NO ) ·6H O was repeatedly impregnated into the pore of SBAꢀ15. As a result of
the weak interaction between the metal ion precursors with Si−OH bonds during the
nanocasting process, it is challenging to fill the mesorpores of silica template
completely. Therefore, the functionalization of silica template by organic groups can
be used to increase the interaction between the organic groups and metal ion precursor,
39
and maximize the quantity of metal ion precursor for good replication. Schüth et al.
have nanocast mesostructured Co with Ia3d symmetry from vinylꢀfunctionalized
3
O
4
cubic mesoporous silica. Despite the great advances, the previous nanocasting
procedure needs multiple impregnation steps, using toxic solvent or surface
32,38,40ꢀ42
1
1
1
1
1
1
1
modification of template by functional agent.
Herein, we report a novel
approach for the fabrication of copperꢀceria mesoporous nanocomposite via
solidꢀstate grindingꢀassisted nanocasting using ethanol as solvent. This oneꢀstep hard
template method not only simplifies the redundant procedures, but also provides a
green and versatile strategy to create mesoporous nanocomposite. This new
copperꢀceria catalyst shows exceedingly high activity in glycerol hydrogenolysis and
exhibited excellent longꢀterm stability for 300 h.
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2. Experimental
2.1 Catalyst preparation
The copperꢀceria mesoporous catalyst was prepared by solidꢀstate
grindingꢀassisted nanocasting method. 1.903 g Cu(NO
3 2 2
) ·3H O (Sinopharm Chemical
Reagent Co., Ltd. (SCRC)), 5.05 g Ce(NO ·6H O (SCRC) and 2.0 g silica template
3
)
3
2
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(including SBAꢀ15 and KITꢀ6, Nanjing XFNANO Materials Technology Co., Ltd)
were mixed with 30 mL ethanol and grounded in a mortar at room temperature.
Subsequently, the mixture was dispersed to 150 mL ethanol solution at room
temperature under vigorous stirring for 24 h. After the ultrasonication for 30 min and
evaporation of ethanol at 80 °C, the sample was calcined at 500 °C for 4 h. Finally,
the silica template was treated three times by 2 M NaOH solution for 24 h. The
asꢀsynthesized samples were labeled as CuCeSBA and CuCeKIT according to the
different silica template, respectively.
The mCeO was fabricated using SBAꢀ15 as a template with the method
2
1
1
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2
2
2
described above. Cu/mCeO
aqueous solution on mCeO
then calcined at 500 °C for 4 h.
CeO nanorods (denoted as rCeO
on the reported procedures. 4.5 mmol Ce(NO ) ·6H O was dissolved in 90 mL
2
was prepared by the impregnation of Cu(NO
3 2 2
) ·3H O
2
. After impregnation, the catalyst was dried at 80 °C and
2
2
) were prepared by hydrothermal method based
43
3
3
2
NaOH solution (6 mol/L) under severe stirring for 10 min at room temperature. After
the mixture transferred into autoclave, hydrothermal treatment was performed at
100 °C for 24 h. Subsequently, the precipitates were collected by centrifugation, dried
at 80 °C overnight, and calcined at 400 °C for 4 h in static air. The Cu/rCeO
synthesized with similar method as Cu/mCeO2.
2
was
2.2 Catalyst characterization
2
N physisorption was measured at –196 °C on a Micromeritics TriStarⅡ 3020
device after the catalysts were pretreated at 250 °C for 8 h in vacuum. BET surface
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area was estimated from the desorption branch of adsorptionꢀdesorption isotherms.
Low angle Xꢀray diffraction (XRD) patterns were measured in D8/maxꢀRA
Xꢀray diffractometer (Bruker, Germany). Wide angle XRD patterns were performed
on a D2/maxꢀRA Xꢀray diffractometer (Bruker, Germany) using Cu Kα radiation at 30
kV and 10 mA with a scanning speed (2θ) of 4°/min. For in situ XRD measurement,
3
ꢀ1
the sample remained in flowing H
2
at a flow rate of 30 cm min and different preset
temperatures. Temperature ramping programs were set from 30 °C to 150, 200, 250,
ꢀ1
300, 350, 400, 450 and 500 °C with a ramping rate of 5 °C min . The XRD patterns
were recorded after the sample temperature reached the preset one for 30 min. The
full width at half maximum (FWHM) of Cu (1 1 1) diffraction at 2θ of 43.2° was
chose to calculate Cu particle size according to Scherrer equation.
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1
1
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2
2
2
TEM and HRTEM were conducted on a JEMꢀ2011F system electron
microꢀscope at 200 kV equipped with a field emission gun. Prior to each test, the
sample was dispersed in ethanol under severe ultrasonication conditions for 20 min
and then deposited on copper grids coated with transparent carbon foil.
Raman spectroscopy was conducted on RenishawꢀUVꢀvis Raman System 1000
using a multichannel air cooled CCD detector at room temperature. An NdꢀYag laser
operating at 532 nm was used as the exciting source with a power of 30 MW.
Temperature programmed reduction of H (H ꢀTPR) was measured in an Auto
2
2
Chem.Ⅱ2920 apparatus (Mircromeritics, USA). At first, ca. 0.10 g sample was
charged into a quartz tube and pretreated in Ar at 150 °C for 30 min. After the catalyst
2
cooled to 30 °C, the Ar flow was changed into 10% H ꢀAr mixed gas. Subsequently, a
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cold trap of 2ꢀpropanolꢀliquid nitrogen slurry was employed to condense the water
vapor. Finally, the catalyst was heated from 30 °C to 500 °C at a ramp rate of
5 °C/min and meanwhile the consumption of hydrogen was recorded by a thermal
conductivity detector (TCD).
NH
catalyst was pretreated in Ar at 400 °C for 20 min, cooled to 100 °C, and saturated
with pure NH for 30 min. Subsequently, the sample was heated to 600 °C at a ramp
3 2
ꢀTPD was performed in the same apparatus as H ꢀTPR. In each run, 0.1 g
3
rate of 10 °C/min and the desorbed NH
detector.
3
was simultaneously monitored by a TCD
1
1
1
1
1
N
2
O chemisorption was conducted in the same equipment as above. The catalyst
sample was loaded into a quartz tube and reduced according to the same H ꢀTPR
2
procedure depicted as above. Subsequently, the catalyst was treated in a 10 vol.%
0
N
2
O/N
2
flow (50 mL/min) for 30 min at 90 °C to oxidize the surface Cu to Cu
2
O.
Finally, the sample was purged by Ar and cooled to 40 °C to start a new H ꢀTPR
2
1
1
1
5
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procedure. The Cu dispersion (DCu) was quantified by the following equation,
D
Cu = 2Y/X
(%)
where Y is the hydrogen consumption in the reduction of Cu O, and X is the
2
1
1
2
2
2
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hydrogen consumption in the reduction of CuO.
XPS was conducted under an ultrahigh vacuum on a VG MiltiLab 2000
spectrometer with Mg Kα radiation and a multichannel detector. Prior to each test, the
2
catalyst was first reduced in H at 250 °C for 2 h in an auxiliary pretreatment chamber
(glove box), and transferred into XPS sample holder. The obtained binding energies
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were calibrated by the C1s peak at 284.6 eV as reference.
ICP optical emission spectroscopy (Optima2100DV, PerkinElmer) was
conducted to analyze the Cu contents of asꢀprepared catalysts.
Cu Kꢀedge Xꢀray absorption spectroscopy (XAS) was measured in transmission
mode at the beam line of Beijing Synchrotron Radiation Facility (BSRF), Institute of
High Energy Physics (IHEP), Chinese Academy of Science (CAS). The XAS spectra
were analyzed on Athena XAS version 0.8.056. Background subtraction and
normalization were processed by fitting linear polynomials to the preꢀedge and
postꢀedge region of absorption spectra, respectively. E value was estimated according
0
1
1
1
1
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2
to the maximum value in the first derivative of the edge region.
2.3 Catalytic test
All the catalytic tests were performed in a vertical fixedꢀbed reactor with an
iceꢀwater trap. Typically, 2.0 g catalyst (20ꢀ40 mesh) was loaded into the constant
temperature section of the reactor with quartz sand fixed in both ends. Subsequently,
the catalyst was in situ reduced at 250 °C and atmospheric pressure for 2 h in flowing
ꢀ1
H
2
(120 mL min ). After reduction, a 10 wt.% glycerol methanol solution was
continuously introduced into the reactor by a microꢀpump along with coꢀfeeding H
2
ꢀ1
(120 mL min ) at 180 °C and 5.0 MPa. The liquid and gas products were cooled
down and collected in a gasꢀliquid separator immersed in an iceꢀwater trap.
The liquid products of glycerol hydrogenolysis were analyzed by a gas
chromatography (GC, Ruihong chromatogram analysis Co., Ltd, China) equipped
with a capillary column (DBꢀWAX, 30 m × 0.32 mm) and a flame ionization detector
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(FID). The tail gas was onꢀline analyzed by a GC (6890N, Agilent, USA) with a
capillary column (OVꢀ101, 60 m × 0.25 mm) and a TCD. These products were also
identified by GCꢀMS (6890N, Agilent, USA). The carbon balance was checked in the
range of 95%ꢀ99%. The quantitative analysis was determined by the following
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6
equations:
moles of glycerol (in) −moles of glycerol (out)
Conversion (%) =
× 100
moles of glycerol (in)
moles of one product
moles of all products
Selectivity (%) =
×100
7
8
The liquid products of xylitol and sorbitol were analyzed by HPLC (Agilent
1260) with a shodex sugar SHꢀ1821 column (300 mm × 8 mm, 5 ꢁm) and a refractive
index detector (RID). The gas products were onꢀline analyzed by GC.
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3. Results and discussion
3.1 Catalyst synthesis and characterization
Scheme 1 shows the preparation procedure of copperꢀceria nanocomposite.
3 2 2 3 3 2
Before the nanocasting, Cu(NO ) ·3H O and Ce(NO ) ·6H O were manually ground
with the hard template (SBAꢀ15 or KIT) in a mortar at room temperature to reach a
homogenous mixture. Subsequently, the mixture was dispersed into ethanol solution
under vigorous stirring. After the evaporation of ethanol, the mixture was calcined to
form mesoporous copperꢀceria composite, and then the silica template was selectively
removed via chemical etching. Notably, solidꢀstate grinding is important to introduce
the precursor species into the channels of mesoporous material and improve the
interaction between metal precursors and silica template. Thereby, this method does
1
0

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not require repeated impregnation of active species into silica template. Additionally,
the synthesized CuCeSBA primarily consisted of short disordered nanorods without
solidꢀstate grinding (Fig. S1†), implying the insufficient pore filling.
44,45
Compared to traditional methods,
the Cu/CeO2 nanocomposites via
nanocasting showed high BET surface area (Table 1). The BET surface area of
2
ꢀ1
2 2
CuCeSBA was up to 160.9 m g , two times as high as that of Cu/mCeO . N
adsorption/desorption isotherms (Fig. S2†) presented typical hysteresis loops and
belonged to type IV, characteristic of mesoporous materials. The ordered mesoporous
structure was verified by lowꢀangle XRD patterns (Fig. S3†). Both the two patterns
displayed a main strong peak at low 2θ value, which were assigned to the (1 0 0) and
1
1
1
1
1
1
1
1
1
1
2
2
2
3
7
(2 1 1) crystalline planes of the p6mm and Ia3d symmetries, respectively. This
indicates the successful replication of CuCeSBA and CuCeKIT from the parent
SBAꢀ15 and KITꢀ6.
As shown in Fig. 1, both the CuCeSBA and CuCeKIT displayed highly ordered
mesoporous structures. TEM images of CuCeSBA was indicative of a hexagonally
packed pore structure with an average diameter of about 7ꢀ8 nm, suggesting the
successful replication from the parent SBAꢀ15. The highꢀresolution TEM image of
reduced CuCeSBA showed various nanocrystallites with wellꢀdefined lattice planes,
corroborating the high crystallinity of the pore walls. The smaller lattice strip of d=
0.208 nm in the pore structure belonged to Cu while in the nearby area another one of
d = 0.310 nm on the framework was assigned to (1 1 1) planes of fluorite CeO
2
30,46
phase,
suggesting that Cu and CeO
2
were dispersed homogenously in the pore
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walls. In addition, the connecting bridges between two nanowires could also be
clearly observed, revealing the strong interaction between Cu and CeO species.
2
Mesoporous CuCeKIT composite, consisting of nanowire arrays, was obtained with
the average pore diameter of 10 nm. The combination of HAADFꢀSTEM (Fig. S4†)
and elemental EDX mapping (Fig. S5†) confirmed the homogenous distribution of Cu,
Ce and O in the mesoporous oxides, indicating that CuO and CeO
2
jointly constructed
the pore wall of mesoporous Cu/CeO nanocomposite. However, Cu nanoparticles
2
were mainly embedded on the internal surface of mCeO
catalyst (Fig. S6†).
2 2
pore wall over Cu/mCeO
1
1
1
1
1
1
1
1
1
1
2
2
2
2
The mCeO with good crystallization was obtained and supported by XRD
analysis (Fig. 2A). The typical diffuse diffraction peaks centered at 28.8°, 33.3°, 47.8°,
56.5°, 59.4° and 69.6° were indexed to the pure faceꢀcenteredꢀcubic structure of (fcc)
3
7
CeO
detected over CuCeSBA and CuCeKIT, suggesting that these Cu species were
highly dispersed or incorporation into the ceria lattice. Contrarily, the Cu/mCeO
exhibited obvious CuO diffraction patterns, reflecting the big Cu nanoparticles. The
ꢀTPR patterns (Fig. 2B) of CuCeSBA and CuCeKIT presented fairly symmetric
2
.
Only extremely weak CuO diffraction patterns at 35.6° and 38.8° were
3
0
2
H
2
reduction peaks at low temperature, presumably implying that only one kind of
nanoꢀsized Cu specie was located on these mesoporous composites because of the
2
formation of monodisperse CuO species. However, Cu/mCeO showed a broad
reduction peak at high temperature, and contained at least two kinds of Cu species,
such as nano and bulk Cu species.
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Strong interaction was convinced by the Raman spectroscopy result (Fig. 2C)
ꢀ1
2
that the characteristic band at 462 cm of F2g vibration mode of CeO lattice shifted
37
remarkably toward low wavenumber over CuCeSBA and CuCeKIT. No shift was
observed over Cu/mCeO . In addition, a new broad band was observed at around
2
ꢀ1
500ꢀ660 cm over CuCeSBA and CuCeKIT, which was ascribed to the structure
44
defects caused by the incorporation of heteroatom copper ions into ceria lattice.
These results from Raman were consistent well with the observation by XPS (Fig.
2D). There was strong electronic interaction between Cu and CeO species in
mesoporous CuCeSBA(KIT) composites, as evidenced by the shift of Cu 2p peak
towards high binding energy. In comparison to Cu/mCeO , the Cu 2p peak of
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
30
CuCeSBA moved from 932.3 eV to 932.7 eV, verifying that the electron
δ+
transformed from Cu to CeO
2
, and led to form Cu . The XPS data can also be
utilized to calculate the content of surface Cu atoms. Despite similar bulk Cu content
from ICP tests (Table 1), CuCeSBA afforded the highest surface Cu content. This was
indicative of the higher surface Cu dispersion of CuCeSBA, in well line with the
result based on N
KIT, 2D hexagonal pore structure of SBAꢀ15 facilitates to restrain CuO and CeO
nanoparticles, forms strong electronic interaction between CuO and CeO species, and
2
O chemisorption (Table 1). Compared to 3D cubic pore structure of
2
2
results in the higher Cu dispersion. Additionally, the poor Cu dispersion of Cu/mCeO2
could tentatively ascribed to the postꢀimpregnation method that the pore confinement
of mesorpores CeO
2
cannot effectively prevent the aggregation of Cu nanoparticles
during heat treatment.
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0
1
2
Because the Raman spectra is a microdomain technique (area < 1 ꢁm) and XPS
explores the catalyst surface (deep < 5 nm), both of them cannot fully reveal the
overall structural information, which can be replenished by XAS spectra. The Cu
Kꢀedge XAS spectra of these Cuꢀbased catalysts showed some interesting results in
2
+
Fig. 3A, B. The CuꢀKꢀedge XANES definitely confirmed the ionic Cu feature for all
the mesoporous copperꢀceria catalysts. The related EXAFS spectra in R space (Fig.
3B) showed a strong contribution on the first shell of Cu−O bond. In bulk CuO, the
4
7
2
corresponding peak located at ca. 1.514 Å. For Cu/mCeO , the characteristic peak
remained and practically unchanged. Nevertheless, this peak underwent remarkable
shift over CuCeSBA and CuCeKIT. Specifically, the peak centered at 1.548 Å over
1
1
1
1
1
1
1
1
1
1
2
2
2
CuCeSBA. This can be caused by the incorporation of CuO to CeO
strong interaction between CuO and CeO species over CuCeSBA and CuCeKIT.
2
It is interesting to explore the thermal stability of CuCeSBA and Cu/mCeO ; in
2
lattice, verifying
2
situ XRD (Fig. 4) was exhibited to monitor the Cu diffraction peaks in flowing H2
upon different temperature. For CuCeSBA, the intensity and sharpness of Cu
diffraction peaks increased slowly in the range of 250ꢀ 600 °C, and the average Cu
particle size determined by Scherrer equation only increased from 4.6 to 10.2 nm (Fig.
4C). Conversely, the Cu particle size sharply increased from 6.7 to 37.0 nm over
Cu/mCeO , reflecting the serious sintering and aggregation of copper nanoparticles
2
upon the same heat treatment. These Cu nanoparticles inside the channels of mCeO
2
cannot be sufficiently stabilized by the pore confinement effect at high temperature,
easily occur interparticle diffusion and subsequent agglomeration.
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3.2 Catalytic performance
Selective hydrogenolysis of glycerol to 1,2ꢀPDO is used to as a model reaction to
evaluate the catalytic behavior of mesoporous copper/ceria catalysts. As illustrated in
Fig. 5A, all the three catalysts obtained high 1,2ꢀPDO selectivity (basically >90%)
because of the higher intrinsic ability to cleave C−O bond in preference to C−C bond
1
3,30
for Cuꢀbased catalysts.
All initial glycerol conversion reached or approached to
100% at low weight hourly space velocity (WHSV). Variations in glycerol conversion
within the series of mesoporous copper/ceria catalysts relate to the differences in
residence time with the change of WHSV. Of them, CuCeSBA gave the lowest
decline rate of glycerol conversion with the increasing WHSV, reflecting its highest
catalytic activity. Turnover frequency (TOF) can be utilized to reveal the intrinsic
active ability and the results are listed in Table 1. The TOF based on accessible
1
1
1
1
1
1
1
1
1
1
2
2
2
ꢀ1
ꢀ1
surface Cu atoms of CuCeSBA was calculated to be 4.8 molglycerol·molCu(surf) ·h and
this value was much higher than that of Cu/mCeO . Under similar conditions, this
2
8
,30,48
TOF was ca. 3~14 times as high as frequently reported Cu/SiO
unequivocally demonstrating the excellent activity of CuCeSBA. Fig. 5B displays a
comparison of longꢀterm performance for the CuCeSBA and Cu/mCeO . The
2
catalysts,
2
CuCeSBA presented unprecedented catalytic behavior and was stable for 300 h.
Contrarily, significant deactivation of Cu/mCeO occurred from 51 h to 171 h, and the
2
conversion decreased to 22.2% in the end.
The excellent catalytic activities presented by CuCeSBA and CuCeKIT
nanocomposites are partly ascribed to the formation of monodisperse Cu
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nanoparticles and high surface Cu dispersion, which is attained through deliberate
design of the catalyst synthesis procedure. The solidꢀstate grindingꢀassisted
hardꢀtemplate method facilitates to form homogenous precursors’ mixture, enhances
the interaction between metal precursors and silica surface during nanocasting,
promotes the infiltration of the precursors into the pore channels, and results in the
synthesis of homogenously dispersed copperꢀceria nanocomposites. Another
important factor is the presence of strong interaction and resultant CuO doped CeO
2
lattice. This can greatly affect planes, corner as well as edge atoms, correspondingly
modify both surface structure and electronic properties, and eventually form new
surface defects. These defects are coordinately unsaturated and endow high catalytic
ability for glycerol activation. Additionally, XPS test confirmed that electron transfer
1
1
1
1
1
1
1
1
1
1
2
2
2
δ+
δ+
from CeO
2
to Cu led to form Cu . The Cu species are favorable to enhance surface
Lewis acidity (Fig. S7†), promote the adsorption and polarization of hydroxyl groups
3
0
of glycerol, and ultimately improve surface reaction rate. This can well explain the
enhanced TOF of CuCeSBA. Finally, the tailored mesoporous structure, which can be
controlled by various silica templates, appears to be another key to determine the
catalytic behavior. When using SBAꢀ15 as template, the obtained copperꢀceria
possesses a small pore size and large wall thickness, which is beneficial to confine
highly dispersed Cu nanoparticles and leads to enhanced reactivity.
Regarding the stability, the confined Cu nanoparticles inside the channels of
2 2
mesoporous mCeO (Cu/mCeO ) cannot effectively restrain their migration, Ostwald
ripening and sintering under longꢀterm reaction. The significant aggregations of Cu
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nanoparticles sharply decreased accessible Cu surface area, and thus led to its rapid
deactivation. Conversely, the existence of strong interaction together with Cu doped
2
CeO lattice in CuCeSBA can restrict Cu nanoparticles migration, further limits their
growth via particle aggregation, and maintain high dispersion of copper species.
Therefore, CuCeSBA exhibited excellent thermal stability and rather steady
performance for glycerol hydrogenolysis under 180 °C and 5.0 MPa H
We also prepared a comparable Cu/rCeO catalyst, wherein Cu nanoparticles
anchored on the external surface of CeO nanorods via postꢀimpregnation. Owing to
the lack of pore confinement effect, the unconfined Cu nanoparticles became
seriously aggregated (Fig. S8†). Expectedly, very poor activity of Cu/rCeO was
observed in glycerol hydrogenolysis, and even much lower than that of Cu/mCeO
2
conditions.
2
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
.
ꢀ1
Under similar WHSV of 0.15 h , 100% and 94.1% conversions of glycerol were
separately given over CuCeSBA and Cu/mCeO , while only 37.2% conversion was
2
obtained for Cu/rCeO . Therefore, sophisticated synthesis approach plays a key role
2
to achieve small and stable Cu nanoparticles and thereby excellent catalytic
performance. Our nanocasting method provides a homogenous copperꢀceria
nanocomposite, wherein the copper has been successfully incorporated into ceria
lattices, and formed highly dispersed and robust Cu nanoparticles. The Cu
nanoparticles of CuCeSBA are smaller, more robust and active than that of Cu/mCeO2,
despite the latter has pore confinement effect. More importantly, from the comparison
of the catalytic activity of various Cu/CeO
2
catalysts, we find that the metal doped
oxide nanocomposite is superior to the counterpart based on pore confinement effect,
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and far superior to unconfined nanoparticles. These results also demonstrate that
highly active and stable Cu nanoparticles can be facilely synthesized by nanocasting
method, by selectively incorporating metal species into the mesorpore of SBAꢀ15 via
solidꢀstate grindingꢀassisted oneꢀstep impregnation after its calcination and sequential
etching.
To explore the versatility of mesoporous CuCeSBA, its catalytic performance
with different sugar alcohol substrates was evaluated and compared (Table 2).
1,2ꢀPDO was predominantly converted to 1ꢀpropanol in 91.2% yield and a small
amounts of 2ꢀpropanol, implying that CuCeSBA preferentially cleaved primary C−O
bond. Similar trend was observed in the case of glycerol. This is related to the higher
barrier for the cleavage secondary C−O bond than that of primary one because of the
1
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1
1
2
2
2
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9
steric hindrance effect.
Hydrogenolysis of 1,3ꢀpropanediol (1,3ꢀPDO) was
exclusively converted to 1ꢀpropanol in 98.2% selectivity. Regarding xylitol and
sorbitol, almost complete conversions were achieved over CuCeSBA, giving high
yields of valued products, including 1,2ꢀPDO, ethylene glycol (EG) and glycerol. The
total yield of 1,2ꢀPDO, EG and glycerol in xylitol hydrogenolysis was up to 71.7%,
which was even superior to the reported noble metal catalysts under similar
17
conditions. Additionally, base promoters like Ca(OH)
2
or KOH are usually required
17,50,51
to promote the cleavage of xylitol and sorbitol C−C bonds,
while our CuCeSBA
did not need any extra additives. The CuCeSBA intrinsically contained large amounts
of acidic sites (Fig. S7†), which was also favorable to break C−C linkages of sorbitol
52,53
and xylitol.
Notably, CuCeSBA showed powerful ability to cleave the C−C as
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well as C−O bonds, and facilely converted sorbitol and xylitol to 1,2ꢀPDO, EG and
glycerol under gentle conditions. However, it is difficult for CuCeSBA to efficiently
break C−C bonds of glycerol. Compared to xylitol and sorbitol, glycerol has a short
carbon chain and should require higher energy barrier to cleave C−C bond.
5
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4. Conclusions
We have presented a facile and simple approach to fabricate mesoporous copper
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2
doped ceria catalyst with oneꢀstep solidꢀstate grindingꢀassisted nanocasting method.
This CuCeSBA nanocomposite exhibited excellent catalytic performance in the
hydrogenolysis of sugar alcohols owing to monodisperse Cu nanoparticles, strong
1
1
1
1
1
1
1
1
1
1
2
2
2
interaction between Cu and CeO
2
species, and tailored mesoporous structure.
lattice provided spatial restriction on
Moreover, the incorporation of CuO into CeO
2
copper nanoparticles, which can hinder their sintering under reaction conditions and
result in an enhanced stability. The Cu doped CeO nanocomposite is superior to the
2
confined Cu/mCeO
2
counterpart, and far superior to unconfined Cu/rCeO
2
nanoparticles. It can be reasonably envisaged that such a lowꢀcost, earthꢀabundant,
environmentally friendly and robust material will hold great potential for a wide range
of metalꢀcatalyzed reactions.
Acknowledgements
We acknowledge the financial support of the National Natural Science Foundation of
China (21403269) and the Youth Innovation Promotion Association CAS (2015140).
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We thank Dr. Pei Sheng for his help with EXAFS technique. Thanks are also given to
Beijing Synchrotron Radiation Facility.
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References
1 S. Zhu, J. Wang and W. Fan, Catal. Sci. Technol. 2015, 5, 3845ꢀ3858.
2 A. M. Ruppert, K. Weinberg and R. Palkovits, Angew. Chem. Int. Ed., 2012, 51
,
2564ꢀ2601.
3 D. Ten, Jeroen and U. Hanefeld, ChemSusChem, 2011,
4
, 1017ꢀ1034.
4 D. Roy, B. Subramaniam and R. V. Chaudhari, ACS Catal., 2011,
1, 548ꢀ551.
1
1
1
1
1
1
1
1
1
1
2
2
5 M. Shiramizu and F. D. Toste, Angew. Chem., 2012, 124, 8206ꢀ8210.
6 Y. Amada, N. Ota, M. Tamura, Y. Nakagawa and K. Tomishige, ChemSusChem
,
2014,
7, 2185ꢀ2192.
7 J. R. Dethlefsen and P. Fristrup, ChemSusChem, 2015,
8, 767ꢀ775.
8 S. Zhu, X. Gao, Y. Zhu, Y. Zhu, H. Zheng and Y. Li, J. Catal., 2013, 303, 70ꢀ79.
9 M. G. Musolino, L. A. Scarpino, F. Mauriello and R. Pietropaolo, ChemSusChem
,
,
,
2011, 4, 1143ꢀ1150.
10 N. D. Kim, J. R. Park, D. S. Park, B. K. Kwak and J. Yi, Green Chem., 2012, 14
2638ꢀ2646.
11 I. Gandarias, P. L. Arias, J. Requies, M. El Doukkali and M. B. Güemez, J. Catal.
2011, 282, 237ꢀ247.
12 S. Xia, R. Nie, X. Lu, L. Wang, P. Chen and Z. Hou, J. Catal., 2012, 296, 1ꢀ11.
2
0

Page 21 of 33
Green Chemistry
View Article Online
DOI: 10.1039/C5GC01766A
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
13 E. S. Vasiliadou, T. M. Eggenhuisen, P. Munnik, P. E. de Jongh, K. P. de Jong and
A. A. Lemonidou, Appl. Catal., B: Environ., 2014, 145, 108ꢀ119.
14 Y. Nakagawa and K. Tomishige, Catal. Sci. Technol., 2011, 1, 179ꢀ190.
15 T. Miyazawa, Y. Kusunoki, K. Kunimori and K. Tomishige, J. Catal., 2006, 240
,
213ꢀ221.
16 N. Li and G. W. Huber, J. Catal., 2010, 270, 48ꢀ59.
17 J. Sun and H. Liu, Green Chem., 2011, 13, 135ꢀ142.
18 I. Gandarias, P. L. Arias, J. Requies, M. B. Guemez and J. L. G. Fierro, Appl.
Catal., B: Environ., 2010, 97, 248ꢀ256.
1
1
1
1
1
1
1
1
1
1
2
2
2
19 C. Deng, X. Duan, J. Zhou, X. Zhou, W. Yuan and S. L. Scott, Catal. Sci. Technol.
2015, , 1540ꢀ1547.
,
5
20 W. Oberhauser, C. Evangelisti, R. P. Jumde, R. Psaro, F. Vizza, M. Bevilacqua, J.
Filippi, B. F. Machado and P. Serp, J. Catal., 2015, 325, 111ꢀ117.
21 J. Oh, S. Dash and H. Lee, Green Chem., 2011, 13, 2004ꢀ2007.
22 F. Mauriello, H. Ariga, M. G. Musolino, R. Pietropaolo, S. Takakusagi and K.
Asakura, Appl. Catal., B: Environ., 2015, 166–167, 121ꢀ131.
23 K. L. Deutsch, D. G. Lahr and B. H. Shanks, Green Chem., 2012, 14, 1635ꢀ1642.
24 S. Zhu, X. Gao, Y. Zhu and Y. Li, J. Mol. Catal. A: Chem., 2015, 398, 391ꢀ398.
25 S. Zhu, Y. Zhu, S. Hao, H. Zheng, T. Mo and Y. Li, Green Chem., 2012, 14
,
2607ꢀ2616.
26 R. Arundhathi, T. Mizugaki, T. Mitsudome, K. Jitsukawa and K. Kaneda,
ChemSusChem, 2013, , 1345ꢀ1347.
6
2
1

Green Chemistry
Page 22 of 33
View Article Online
DOI: 10.1039/C5GC01766A
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
27 P. K. Vanama, A. Kumar, S. R. Ginjupalli and V. R. C. Komandur, Catal. Today
2015, 250, 226ꢀ238.
,
,
,
,
28 J. Ge, Z. Zeng, F. Liao, W. Zheng, X. Hong and S. C. E. Tsang, Green Chem.
2013, 15, 2064ꢀ2069.
29 E. S. Vasiliadou, V. L. Yfanti and A. A. Lemonidou, Appl. Catal., B: Environ.
2015, 163, 258ꢀ266.
30 S. Zhu, X. Gao, Y. Zhu, W. Fan, J. Wang and Y. Li, Catal. Sci. Technol., 2015,
5
1169ꢀ1180.
31 X. Jin, L. Dang, J. Lohrman, B. Subramaniam, S. Ren and R. V. Chaudhari, ACS
Nano, 2013, , 1309ꢀ1316.
32 C. Wen, Y. Zhu, Y. Ye, S. Zhang, F. Cheng, Y. Liu, P. Wang and F. Tao, ACS
Nano, 2012, , 9305ꢀ9313.
1
1
1
1
1
1
1
1
1
1
2
2
7
6
33 G. Prieto, M. Shakeri, K. P. de Jong and P. E. de Jongh, ACS Nano, 2014, 8,
2522ꢀ2531.
34 F. Wang, R. Shi, Z.ꢀQ. Liu, P.ꢀJ. Shang, X. Pang, S. Shen, Z. Feng, C. Li and W.
Shen, ACS Catal., 2013, , 890ꢀ894.
3
35 H. Yue, Y. Zhao, S. Zhao, B. Wang, X. Ma and J. Gong, Nat. Commun., 2013,
2339.
4
,
36 Y. Ren, Z. Ma and P. G. Bruce, Chem. Soc. Rev., 2012, 41, 4909ꢀ4927.
37 H. Yen, Y. Seo, S. Kaliaguine and F. Kleitz, Angew. Chem. Int. Ed., 2012, 51
,
12032ꢀ12035.
2
2

Page 23 of 33
Green Chemistry
View Article Online
DOI: 10.1039/C5GC01766A
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
38 H. Yen, Y. Seo, R. GuilletꢀNicolas, S. Kaliaguine and F. Kleitz, Chem. Commun.
2011, 47, 10473ꢀ10475.
,
39 F. Schüth, Adv. Mater., 2005, 17, 53ꢀ56.
40 A. Rumplecker, F. Kleitz, E.ꢀL. Salabas and F. Schüth, Chem. Mater., 2007, 19
485ꢀ496.
,
41 P. Djinović, J. Batista and A. Pintar, Catal. Today, 2009, 147S, S191ꢀS197.
42 H. Tüysüz, E. L. Salabaꢂ, E. Bill, H. Bongard, B. Spliethoff, C. W. Lehmann and F.
Schüth, Chem. Mater., 2012, 24, 2493ꢀ2500.
43 R. Si and M. FlytzaniꢀStephanopoulos, Angew. Chem. Int. Ed., 2008, 47
,
1
1
1
1
1
1
1
1
1
1
2
2
2
2884ꢀ2887.
44 W.ꢀW. Wang, P.ꢀP. Du, S.ꢀH. Zou, H.ꢀY. He, R.ꢀX. Wang, Z. Jin, S. Shi, Y.ꢀY.
Huang, R. Si, Q.ꢀS. Song, C.ꢀJ. Jia and C.ꢀH. Yan, ACS Catal., 2015,
5,
2088ꢀ2099.
45 A. Aranda, E. Aylon, B. Solsona, R. Murillo, A. M. Mastral, D. R. Sellick, S.
Agouram, T. Garcia and S. H. Taylor, Chem. Commun., 2012, 48, 4704ꢀ4706.
46 L. Wan, X. Cui, H. Chen and J. Shi, Mater. Lett., 2010, 64, 1379ꢀ1382.
47 J. S. Elias, M. Risch, L. Giordano, A. N. Mansour and Y. ShaoꢀHorn, J. Am. Chem.
Soc., 2014, 136, 17193ꢀ17200.
48 Z. W. Huang, F. Cui, H. X. Kang, J. Chen, X. Z. Zhang and C. G. Xia, Chem.
Mater., 2008, 20, 5090ꢀ5099.
49 M. R. Nimlos, S. J. Blanksby, X. Qian, M. E. Himmel and D. K. Johnson, J. Phys.
Chem. A, 2006, 110, 6145ꢀ6156.
2
3

Green Chemistry
Page 24 of 33
View Article Online
DOI: 10.1039/C5GC01766A
1
2
3
4
5
6
7
50 L. Zhao, J. H. Zhou, Z. J. Sui and X. G. Zhou, Chem. Eng. Sci., 2010, 65, 30ꢀ35.
51 M. Banu, S. Sivasanker, T. M. Sankaranarayanan and P. Venuvanalingam, Catal.
Commun., 2011, 12, 673ꢀ677.
52 D. Liang, C. Liu, S. Deng, Y. Zhu and C. Lv, Catal. Commun., 2014, 54, 108ꢀ113.
53 I. M. Leo, M. L. Granados, J. L. G. Fierro and R. Mariscal, Chin. J. Catal., 2014,
35, 614ꢀ621.
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Scheme 1 The procedure of oneꢀstep solidꢀstate grindingꢀassisted nanocasting for the
3
4
preparation of mesoporous copperꢀceria nanocomposite.
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Table 1 The physicochemical properties and turnover frequency (TOF) of various
Cuꢀbased catalysts
Catalyst
S
BET
2
Pore volume Pore size Cu content Surface Cu Cu dispersion TOF
ꢀ1 a
3
ꢀ1 a
a
b
c
d
ꢀ1 e
(
m g )
(cm g )
(nm)
7.8
(wt%)
16.59
content (at%) (%)
(h )
CuCeSBA
CuCeKIT
160.9
86.8
69.3
0.332
17.5
12.7
8.5
24.9
4.8
4.1
3.4
0.224
0.193
10.1
11.1
17.74
20.2
Cu/mCeO
2
16.63
13.8
a
b
c
d
Determined by N2 physisorption. tested by ICP. calculated based on XPS. determined by N O
2
e
chemisorption. TOF is moles of converted glycerol per mole of surface Cu sites and per hour. The reaction
conditions were chosen to determine the rate below 20% conversion.
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Table 2 Catalytic performance for the hydrogenolysis of different substrates over
a
CuCeSBA catalyst
Entry Substrate
Conversion Product selectivity
(
%)
(%)
1
2
HO
OH
100
1,2ꢀPDO (96.9%)
OH
glycerol
HO
100
1ꢀpropanol (91.2%),
OH
2
ꢀpropanol (7.8%)
1
,2ꢀPDO
3
4
HO
OH
93.5
100
1ꢀpropanol (98.2%)
1
,3ꢀPDO
b
OH
1,2ꢀPDO (41.5%), EG
HO
OH
OH
OH
(24.5%), glycerol (5.7%)
xylitol
OH
OH
b
5
OH 99.2
1,2ꢀPDO (32.4%), EG
HO
OH
OH
(10.8%), glycerol (6.8%)
sorbitol
a
Reaction conditions: 180 °C, 5.0 MPa, H
2
/glycerol = 100:1 (molar
b
ratio); 220 °C.
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A
C
1
0 nm
1
D
0
. 31 0n m
2
n m
1
00 nm
2
3
Fig. 1 Representative TEM or HRTEM images of (A) CuCeSBA, (B) CuCeSBA, (C)
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CuCeSBA, (D) CuCeKIT.
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Fig. 2 (A) XRD, (B) H ꢀTPR and (C) Raman spectra of calcined Cuꢀbased catalysts;
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(D) Cu 2p XPS photoemission peaks of reduced Cuꢀbased catalysts.
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